THE EFFECT OF AVOCADO CONSUMPTION ON FOOD DISPLACEMENT IN TERMS OF
CARDIOVASCULAR DISEASE RISK
A Thesis
Presented to the
Faculty of
California State Polytechnic University, Pomona
In Partial Fulfillment
Of the Requirements for the Degree
Master of Science
In
Agriculture
By
Yee‐Chi (Christina) Chen
2014
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SIGNATURE PAGE
THESIS: THE EFFECT OF AVOCADO CONSUMPTION ON FOOD DISPLACEMENT IN TERMS OF CARDIOVASCULAR DISEASE RISK
AUTHOR: Yee-Chi (Christina) Chen
DATE SUBMITTED: Spring 2014
College of Agriculture
Dr. Bonny Burns-Whitmore, RD______Thesis Committee Chair Human Nutrition and Food Science
Dr. David Edens ______Human Nutrition and Food Science
Dr. Harmit Singh ______Human Nutrition and Food Science
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ABSTRACT
Many functional foods have been studied for their ability to lower cardiovascular disease (CVD) risk. Avocados contain significant amounts of cardioprotective components such as monounsaturated fats, polyunsaturated fats, antioxidants, fiber, and potassium, among other nutrients (4). Most studies have been done on the direct health effects of avocado consumption, whereas few have looked at its ability to affect overall diet pattern (5,6). In the present study, the ability of the avocado to affect diet in terms of lowering CVD risk was studied through evaluating nutrient profile, nutrient displacement, and correlation between changes in nutrient intake and changes in plasma cholesterol of 13 free‐living college students.
Participants underwent a 4‐week avocado‐free diet period before the 8‐week treatment period of 5 oz of avocado/day. 24‐hour dietary recalls were collected and blood samples were drawn for lipid profile analyses. Nutrients of interest selected for analyses were based on their ability to affect CVD risk, including but not limited to antioxidant and dietary fat components.
Although the results obtained was almost consistently insignificant with the exception of soluble fiber displacement, results still indicated a pattern in compositional and displacement values of MUFA, PUFA, soluble fiber, and total energy intake that supports previous findings of improved diet quality with avocado consumption (Fulgoni et al., 2013). It can’t be concluded that avocados should be recommended as a supplement to obtain the cardiovascular benefits.
However, these results should be regarded as a basis for future research where they can be reexamined and reevaluated.
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TABLE OF CONTENTS
Signature Page ...... ii
Abstract ...... iii
List of Tables...... v
Chapter 1: Introduction ...... 1
Chapter 2: Literature Review ...... 11
Chapter 3: Methods ...... 33
Chapter 4: Results ...... 42
Chapter 5: Discussion ...... 51
Chapter 6: Conclusion ...... 71
References ...... 73
Appendix A: IRB Approval Letter ...... 86
Appendix B: 24‐Hour Recall Worksheet...... 88
Appendix C: Participant characteristics from Cal Poly Avocado Study...... 91
Appendix D: Research certificate...... 93
Appendix E: Journal Article...... 95
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LIST OF TABLES
Table 1 Nutrient Composition of Hass Avocado (per 1 Fruit, 5 oz) ...... 14
Table 2 Comparison between Nutrient Profiles of Hass Avocado, Almonds, Pistachios, and Walnuts ...... 17
Table 3 Clinical Trials that have Examined the Effect of Avocado Consumption on Cardiovascular Disease Risk as Measured by the Lipid Profile ...... 18
Table 4 Summary of Studies that Support Nutrient Components Found in Fruit and Vegetables that Lower CVD Risk ...... 22
Table 5 Summary of Studies that Examined the Effect of Fatty Acids on Lipid Profile ...... 26
Table 6 Nutrient Components Analyzed for this Study ...... 38
Table 7 Mean Diet Compositional Changes of Participants between the Two Study Periods ...... 44
Table 8 Mean Nutrient Displacement Values ...... 46
Table 9 Associations between Nutrient Displacement or Intake and Plasma Lipids ...... 50
Table 10 Summary for Diet Compositional Changes that Lower and Raise CVD Risk ...... 56
Table 11 Summary of Nutrient Displacement Values that Lower and Raise CVD Risk ...... 62
Table 12 Two‐tailed t‐Test Results for Group Differences in Baseline Participant Characteristics ...... 95
Table 13 Post Hoc Statistical Power and Required Sample Size Calculations for Diet Composition ...... 67
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Table 14 Post Hoc Statistical Power and Required Sample Size Calculations for Nutrient Displacement ...... 68
Table 15 Post Hoc Statistical Power and Required Sample Size Calculations for Associations ...... 69
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CHAPTER 1
INTRODUCTION
Statement of the Problem
Cardiovascular disease (CVD) has been found to be the leading cause of morbidity and mortality in Americans (Lichtenstein et al., 2006). The American Heart Association,
National Cholesterol Education Program, Dietary Guidelines for Americans, and Total
Lifestyle Change program are some examples of the effort put forth by government as well as voluntary organizations to reduce the risk of CVD in the US population (Lichtenstein et al.,
2006; National Heart, Lung, and Blood Institute (NHLBI), 2001; U.S. Department of
Agriculture (USDA) and U.S. Department of Health and Human Services (USDHHS), 2010;
NHLBI, 2005). What is consistent among these guidelines is the restriction of saturated fat, trans fat, and cholesterol intake along with consumption of fish and other sources of polyunsaturated or monounsaturated fats. Diets rich in fruit and vegetables are promoted as they are excellent sources of fiber and antioxidants. Other restrictions include added sugars and sodium. These guidelines are based on research findings that have found these nutrient components to be contributing factors to the development of CVD. Functional foods, defined by the US Institute of Medicine as “any food or food ingredient that may provide a health benefit beyond the traditional nutrients it contains”, have been a research area of intensive interest (Institute of Medicine/National Academy of Sciences (IOM/NAS),
1 1994). Examples of these foods include nuts such as almonds, pistachios, and walnuts
among numerous other food items studied for their cardiprotective functions (Dreher &
Davenport, 2013). Cardioprotective properties of these tree nuts have been compared to the avocado fruit due to their similar nutritional components. Although the research on several of these foods are extensive, most focus on the direct health implications determined by measures such as lipid profiles (Jaceldo‐Siegl, Sabat`e, Rajaram, & Fraser,
2004). Since nutritional guidelines target the overall diet, there should be a measure of how a functional food can affect the overall diet pattern besides its direct biological effects.
Avocado
Research shows that the consumption of avocado has led to improved lipid profile, anthropometric measures, overall diet quality, and satiety (Jaceldo‐Siegl et al., 2004; Grant,
1960; Colquhoun, Moores, Somerset, & Humphries, 1992; Carranza et al., 1995; Lopez‐
Ledesma, Frati Munari, & Hernandez Domingquez, 1996; Fulgoni, Dreher, & Davenport,
2013; Wein, Haddad, Oda, & Sabate, 2013). Findings suggest that the avocado fruit can be incorporated into the diet for its benefits in lowering CVD risk. In determining the ability of the avocado to affect the overall diet pattern of the consumer, we can more effectively evaluate its impact on CVD risk. Furthermore, an examination into how much of the resulting changes in lipid profile can be attributed to these diet pattern changes can provide a deeper understanding of its health benefits.
2 Food Displacement
The effect of avocado consumption on the overall diet pattern was measured by food displacement (Jaceldo‐Siegl et al., 2004). This measure is defined by Jaceldo‐Siegl as “an inverse measure of the degree to which the supplement induced a change in the content of a particular nutrient in the supplemented diet” (Jaceldo‐Siegl et al., 2004). Results from her study done on almond‐supplementation suggested that almonds were able to induce an overall change in diet pattern to support cardioprotection and meet guidelines for lowering
CVD risk. Although existing literature supports avocado consumption in lowering CVD risk, there seems to lack research that focuses on its ability to lower CVD risk in terms of its effect on the overall diet pattern.
Purpose of the Study
The general purpose of this study is to address the lack of knowledge in the field of overall dietary impact as a result of avocado consumption. Based on the similarity between nutrient profile and heart‐health claims of some tree nuts and avocados, we examined the ability of avocados to affect the overall diet pattern as almond supplementation did (Jaceldo‐Siegl et al., 2004).
Specifically, we will be examining dietary impact via 1) calculating diet composition
changes of selected nutrients, 2) calculating nutrient displacement percentages of selected nutrients, and 3) examining the association between nutrient displacement and changes in
3 the lipid profile components. The nutrients of interest will be selected based on existing
research findings on their ability to affect CVD risk. Lipid profile components will include total cholesterol (TC), low‐density‐lipoprotein cholesterol (LDL), high‐density lipoprotein cholesterol (HDL), and ratios of TC:HDL and LDL:HDL.
Statement of the Hypotheses
The following hypotheses will be listed according to the specific objective they are addressing.
Diet Composition
1. H0: Total calories consumed, monounsaturated and polyunsaturated fat, fiber, and
antioxidant vitamin and minerals will be the same in the avocado‐supplementation
period and the avocado‐free period.
Ha: Total calories consumed, MUFA and PUFA, fiber, and antioxidant vitamin and minerals
will be significantly greater in the avocado‐supplementation period than in the avocado‐
free period.
2. H0: Carbohydrates, cholesterol, saturated and trans fats will be the same in the avocado‐
supplementation period and the avocado‐free period.
Ha: Carbohydrates, cholesterol, saturated and trans fats will be significantly lower in the
avocado‐supplementation period than in the avocado‐free period.
4 Food Displacement
3. H0: Displacement of MUFA and PUFA, fiber, and antioxidant vitamin and minerals in the
avocado‐supplemented period relative to the avocado‐free period will be 0%.
Ha: Displacement of MUFA and PUFA, fiber, and antioxidant vitamin and minerals in the
avocado‐supplemented period relative to the avocado‐free period will be<0% or < 100%.
4. H0: Displacement of carbohydrate and saturated fat in the avocado‐supplementation
period relative to the avocado‐free period will be 0%.
Ha: Displacement of carbohydrate and saturated fat in the avocado‐supplementation
period relative to the avocado‐free period will be > 100%.
Association with Lipids
5. H0: Displacement of monounsaturated fat will not be associated with change in plasma
total cholesterol, LDL, and TC:HDL.
Ha: Displacement of monounsaturated fat will be positively associated with change in
plasma total cholesterol, LDL, and TC:HDL.
6. H0: Displacement of fiber will not be associated with change in plasma total cholesterol,
LDL, and TC:HDL.
Ha: Displacement of fiber will be positively associated with change in plasma total
cholesterol, LDL, and TC:HDL.
5 7. H0: Displacement of PUFA will not be associated with change in plasma LDL and LDL:HDL.
Ha: Displacement of PUFA will be positively associated with change in plasma LDL and
LDL:HDL.
8. H0: Displacement of antioxidants will not be associated with change in plasma LDL and
LDL:HDL.
Ha: Displacement of antioxidants will be positively associated with change in plasma LDL
and LDL:HDL.
9. H0: Displacement of carbohydrate will not be associated with change in HDL and change
in TC:HDL.
Ha: Displacement of carbohydrate will be positively associated with change in HDL and
negatively associated with change in TC:HDL.
10. H0: Change in trans fat intake will not be associated with change in HDL and change in
TC:HDL.
Ha: Change in trans fat intake will be positively associated with change in HDL and
negatively associated with change in TC:HDL.
11. H0: Change in dietary cholesterol intake will not be associated with change in plasma
HDL.
Ha: Change in dietary cholesterol intake will be positively associated with change in
plasma HDL.
6 12. H0: Displacement of total calories, carbohydrate, and saturated fat will not be associated
with change in plasma total cholesterol and LDL.
Ha: Displacement of total calories, carbohydrate, and saturated fat will be negatively
associated with change in plasma total cholesterol and LDL.
Significance of the Study
The dietetics profession often utilizes the knowledge pool provided by nutrition research on functional foods such as the avocado to aid in the counseling of clients. In order to effectively and more accurately cater to dietary needs of an individual, dietetics professionals need to thoroughly understand health implications of food items they are recommending. Since nutrition is a science where the relationships and interactions between nutrients are important considerations in health effects, dietitians not only have to realize the direct biological effects such as changes in biochemistry, they need to pay attention to changes in dietary patterns as a whole as well. This study aims to address the gap in literature regarding the effect of avocados on overall diet patterns. Additionally, it provides further support for the consumption of whole foods over individual supplements in promoting a healthy diet (Ye, Li, & Yuan, 2013).
Besides equipping the dietetics professionals with more knowledge on the context of supplementing avocados in a diet, economic implications are also present for this study.
Per capita consumption of fresh avocado has steadily increased between 1994 and 2012
7 with grower prices remaining relatively stable throughout this period of approximately 200%
increase in consumption (Carman, Saitone, & Sexton, 2013). This tells us that demand for avocados is significant, and the current study can provide further understanding of the full benefits of the fruit, leading to a better‐informed public as well as economic opportunity.
Definitions
Cardiovascular Disease (CVD). CVD refers to a cluster of health conditions including, but not limited to, hypercholesterolemia, atherosclerosis, hypertension, diabetes, and heart failure (Cai & Harrison, 2000). The AHA describes it as equivalent to “heart disease” or
“coronary heart disease”, referring to health problems related to plaque buildup in the arterial walls, as in atherosclerosis (“What is heart disease?”, n.d.). Heart attack and stroke can result from heart disease. The AHA guidelines provide dietary as well as other lifestyle recommendations to help lower the CVD risk (Lichtenstein et al., 006).
Monounsaturated Fatty Acid (MUFA). MUFAs are fatty acids that contain only one double
bond (Mahan, Escott‐Stump, & Raymond, 2012).
Polyunsaturated Fatty Acid (PUFA). PUFAs are fatty acids that contain two or more double bonds (Mahan et al., 2012).
Trans‐Fatty Acids. Trans‐fatty acids are fatty acids that have carbons participating in a
double bond arranged on either side of the double bond, causing it to pack into the membrane as if they were fully saturated (Mahan et al., 2012).
8 Saturated Fatty Acids. Saturated fatty acids are fatty acids that contain only single bonds
(Mahan et al., 2012).
Antioxidant. Antioxidants refer to any molecule that has the ability to stabilize or deactivate free radicals, preventing them from attacking cells or its components and reducing or eliminating oxidative stress (Raman, 2007). Antioxidants can be endogenous, in the form of enzyme systems, or exogenous, obtained from the diet.
Food Displacement. Food displacement can be measured as percentage nutrient
displacement (Jaceldo‐Siegl et al., 2004). “This is an inverse measure of the degree to which the supplement induced a change in the content of a particular nutrient in the supplemented diet.”
Low‐Density Lipoprotein (LDL). LDL is a cholesterol‐carrying lipoprotein in the plasma
produced by the liver (Lichtenstein et al., 2006). As levels of LDL increase, so does the risk for CVD. In elevated CVD risk, there is an accumulation of LDL in the plasma eventually leading to endothelial dysfunction (Mahley, Innerarity, & Weisgraber, 1984). Optimal levels for LDL are set at <100 mg/dL (Lichtenstein et al., 2006). Dietary influences on LDL levels include intake of saturated fatty acids and trans fatty acids.
High‐Density Lipoprotein (HDL). HDL levels have been inversely related to the risk of CVD
(Lichtenstein et al., 2006). This relationship is mostly due to its role in reverse cholesterol transport where cholesterol from peripheral tissues are returned to the liver for excretion.
9 Levels <50 mg/dL in women and <40 mg/dL in men are associated with risk of metabolic
syndrome.
Total Cholesterol (TC). This is a measure of non‐HDL and HDL particles in the plasma (Tian et al., 2011). Elevated plasma TC is a marker for increased CVD risk.
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CHAPTER 2
LITERATURE REVIEW
Cardiovascular Disease and the American Heart Association Diet
Cardiovascular disease (CVD) is a cluster of health conditions including hypercholesterolemia, atherosclerosis, hypertension, diabetes, and heart failure (Cai &
Harrison, 2000). It has long been a leading cause of morbidity and mortality in the US population (Lichtenstein et al., 2006). Several factors contribute to the development of
CVD, including oxidative stress, excessive dietary fat intake, and other lifestyle factors that lead to deterioration of vascular health (Cai & Harrison, 2000; Siri‐Tarino, Sun, Hu, & Krauss,
2010).
Oxidative stress is usually present in the form of reactive oxygen species (ROS). They
are molecules with unpaired electrons, examples of which are superoxide anion, hydroxyl radical, nitric oxide and lipid radicals. ROS are usually produced through radical chain reactions where one ROS molecule attacks another molecule and transforms it into an ROS which can go on to do the same (Betteridge, 2000).
Endothelial dysfunction results from increased oxidative stress interfering with the bioavailability of nitric oxide, causing platelet aggregation, loss of vasodilation, inflammation, and smooth muscle cell growth (Cai & Harrison, 2000). In the presence of
ROS, the nitric oxide‐generating enzyme, endothelial nitric oxide synthase (eNOs) also loses
11
its ability to generate nitric oxide and instead further contributes to the oxidative stress by generating more ROS (Förstermann & Li, 2011).
Dietary fats is also a major component in determining CVD risk (Fernandez & West,
2005). It plays a role in modulating plasma cholesterol concentrations. Intake of certain dietary fats such as saturated and trans fatty acids have been shown to increase CVD risk by increasing plasma LDL levels. Oxidation of LDL particles that migrate across endothelial cell walls become oxidized by oxygen radicals (Davies & Woolf, 1993). Upon being taken up by monocytes that are attracted to the site in response to inflammatory signaling, a foam cell is formed. Intercellular lipids in the foam cell accumulate until it eventually bursts and leads to thrombus and plaque formation.
In an effort to reduce the CVD risk of the US population, organizations such as the
American Heart Association (AHA) has come up with guidelines for dietary and lifestyle recommendations (Lichtenstein et al., 2006). The AHA 2006 Diet and Lifestyle
Recommendations for Cardiovascular Disease Risk Reduction states the importance of balanced calorie intake for healthy body weight maintenance, consumption of fruit and vegetables, whole‐grain, high‐fiber alternatives, oily fish, and restricted intake of saturated fat, trans fat, cholesterol, added sugar, and sodium, among a few other points (Lichtenstein et al., 2006). These guidelines will be addressed once again as we look at the change in diet composition of the participants in the present study in terms of CVD risk.
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Avocado Nutrient Composition
Hass avocado became the leading global avocado variety in the 1970s, when a significant expansion of the industry occurred (Witney, Arapia, Clegg, & Douhan, 2005).
Health benefits from the avocado fruit are mostly attributed to its MUFA‐rich oils, found in a water‐based matrix that improves the bioavailability of its nutrients as well as the taste and texture from its high dietary fiber content (Unlu, Bohn, Clinton, & Schwartz, 2005).
Avocados are categorized as a medium energy dense fruit due to 80% of its edible portion being made up of water and dietary fiber, suggesting benefits in weight control (Bes‐
Rastrollo et al., 2008). A detailed analysis of its nutritional components is listed in Table 1.
13 Table 1
Nutrient Composition of Hass Avocado (per 1 Fruit, 5 oz).
Value Value Value Value Nutrient Nutrient Nutrient Nutrient per 5 oz per 5 oz per 5 oz per 5 oz Vitamin E Sodium Weight (g) 142 Fiber (g) 9.656 (alpha‐toc) 2.7974 11.36 (mg) (mg) Soluble Calories (kcal) 237.14 2.8968 Folate (mcg) 126.38 Zinc (mg) 0.9656 fiber (g) Fat calories Vitamin K 196.812 Sugar (g) 0.426 29.82 Choline 36.352 (kcal) (mcg) Pantothenic Fat (g) 21.868 Water (g) 102.666 2.0732 acid (mg) Saturated fat Vitamin A Calcium 27.2214 9.94 18.46 (kcal) (RAE) (mg) Saturated fat Carotene Copper 3.0246 21.016 0.2414 (g) (RE) (mg) Beta‐
MUFA (g) 13.916 carotene 89.46 Iron (mg) 0.8662 (mcg) Vitamin B1 Magnesium PUFA (g) 2.5844 0.1136 41.18 (mg) (mg) Vitamin B2 Manganese Omega 3 (g) 0.21868 0.1988 0.213 (mg) (mg) Vitamin B3 Phosphorou Omega 6 (g) 2.9536 2.7122 76.68 (mg) s (mg) Vitamin B6 Potassium Protein (g) 2.7832 0.4118 719.94 (mg) (mg) Carbohydrate Vitamin C Selenium 12.2688 12.496 0.568 (g) (mg) (mcg)
(U.S. Department of Agriculture (USDA), 2011)
Several of the nutrient components of the avocado have cardioprotective properties similar to some tree nuts such as almonds, pistachios, and walnuts. All share a similar
14 nutrient profile as well (Table 2) (USDA, 2011). The nutrients that have cardioprotective
properties include fatty acids, dietary fiber, sugars, potassium, magnesium, antioxidant vitamins, vitamin K, B vitamins, carotenoids, phenolics, and phytosterols.
The fatty acids are made up of 71% MUFA, 13% PUFA, and 16% saturated fatty acids.
The composition of these fatty acids change according to seasonal growth stages, e.g. saturated fat decreases while the monounsaturated oleic acid increases as ripening progresses (Lu et al., 2009).
The carbohydrates in the avocado are made up of approximately 80% dietary fiber which is 70% insoluble and 30% soluble (Marlett & Cheung, 1997). Containing a very minimal sugar content of sucrose, glucose, and fructose, the avocado has a glycemic index of approximately zero, making it an excellent food source in blood glucose control and weight management (Roth et al., 2009). The predominant sugar in the avocado is a seven‐carbon sugar called D‐mannoheptulose, which is not included as a sugar as it does not have the same biological effects as conventional sugar (Shaw, Wilson, & Knight, 1980). Rather, it is classified under the phytochemical component.
Avocados contain a very significant amount of potassium, a mineral that has been linked with lowering blood pressure (Whelton et al., 1997). At the same time there is very little sodium present, which is a mineral recommended in minimal amounts by the AHA
15 guidelines (Lichtenstein et al.,2006). The fruit is also a good source of magnesium, low
levels of which has been linked with cardiac ischemia (Institute of Medicine (IOM), 1997).
Vitamins C and E are antioxidants present in significant levels in the avocado. Clinical studies have shown that vitamin C and E in combination may slow atherosclerosis in individuals with hypercholesterolemia (Salonen et al., 2003). Vitamins K and B can lead to increased CVD risk (IOM, 2001; IOM, 1998).
Phytochemicals in avocados include carotenoids, phenolics, and phytosterols.
Avocados have the highest lipophilic total antioxidant capacity among fruits and vegetables
(Wu, Beecher, Holden, Haytowitz, & Prior, 2004). Xanthophylls are the primary carotenoids found in avocados, which include beta‐carotene, lutein, cryptoxanthin, and zeaxanthin.
Higher plasma xanthophyll levels were found to be inversely related to the progression of vascular wall thickening that occurs in atherosclerosis (Dwyer, Paul‐Labrador, Fan, Shircore,
Bairey‐Merz, & Dwyer, 2004). Carotenoid and fatty acid levels increase as the season progresses from January to September (Lu et al., 2009). Absorption of carotenoids and phytosterols from avocados is enhanced due to the unsaturated oil and water matrix of the fruit (Ashton et al., 2006; Deuster, 2001). Phenolics present in the fruit reduces CVD risk by reducing oxidative and inflammatory stress (Chong, Macdonald, & Lovegrove, 2010).
Having a total antioxidant capacity of 600 micromol Trolox Equivaent (TE) per 30 g of fruit, it is classified in the mid‐range of fruit phenolic levels (Wu et al., 2004).
16 Table 2
Comparison between Nutrient Profiles of Hass Avocado, Almonds, Pistachios, and Walnuts.
Hass avocado Almonds Pistachios Walnuts Nutrient (136 g, 1 fruit) (42.5 g, 1.5 oz) (42.5 g, 1.5 oz) (42.5 g, 1.5 oz) Water (g) 98.4 1.1 0.8 1.7 Calories (kcal) 227 254 240 278 Total fat (g) 21.0 22.1 19.1 27.7 MUFA (g) 13.3 13.8 10.1 3.8 PUFA (g) 2.5 5.5 5.7 20 Saturated fat (g) 2.9 1.7 2.3 2.6 Protein (g) 2.7 9.0 9.0 6.5 Total carbohydrate (g) 11.8 9.0 12.2 5.8 Dietary fiber (g) 9.2 4.6 4.2 2.9 Potassium (mg) 690 303 450 188 Magnesium (mg) 39.0 120 48 68 Vitamin C (mg) 12.0 0 1.4 0.6 Folate (mcg) 121 23 21 42 Vitamin B‐6 (mg) 0.4 0.05 0.5 0.2 Niacin (mg) 2.6 1.5 0.6 0.5 Riboflavin (mg) 0.2 0.4 0.1 0.06 Thiamin (mg) 0.1 0.04 0.3 0.15 Pantothenic acid (mg) 2.0 0.1 0.2 0.2 Vitamin K (mcg) 28.6 0 6.3 1.2 Vitamin E, alpha‐toc 2.7 10.1 0.9 0.3 (mg) Gamma‐toc (mg) 0.44 0.3 9.0 8.9 Lutein+zeaxanthin 369 0 494 4.5 (mcg) Total phytosterols 113 54 123 30 (mg)
(USDA, 2011)
17
Avocado Clinical Trials
There is limited research done on CVD and avocado consumption. Clinical trials that have used avocados are summarized in Table 3.
Table 3
Clinical Trials that have Examined the Effect of Avocado Consumption on Cardiovascular
Disease Risk as Measured by the Lipid Profile.
Objectives Methods Findings Reference
Evaluate avocado N=16, patients from Subjects showed both (Grant, 1960) consumption on the Veteran’s unchanged total serum cholesterol Administration cholesterol (TC) and and phospholipids. Hospital In Coral significantly lowered Gales, Florida, aged total cholesterol by 9‐ 27‐72. 43%. 75% of subjects Dietary supplement: had lost weight or Fuerte and Hass maintained weight. avocado variety; 0.5‐ 1.5 avocados consumed per day. Compare the effects N=15, females, aged Both diets lowered TC, (Colquhoun of an avocado‐ 37‐58 but AE decreased by et al., 1992) enriched (AE) diet Dietary supplement: 8.2% whereas AHA‐III and high‐ AE diet followed by lowered by 4.9%. LDL carbohydrate (AHA‐ AHA‐III diet, 3 weeks and apo B decreased III) diet on lipid each. significantly in AE but profile. not AHA‐III. HDL didn’t change in AE but decreased by 13.9% in AHA‐III.
18 Table 3 continued
Objectives Methods Findings Reference
Study effects of N=16, Both diets significantly (Carranza et avocado hypercholesterolemic reduced TC and LDL. al., 1995) consumption via two patients with Triglycerides were diets on plasma lipid phenotype I and II slightly raised by diet 2 concentrations in dyslipidemias. Dietary and mildly reduced by dyslipidemia supplement: Diet 1) diet 1. HDL was patients. avocado rich diet significantly increased in (75% fat from diet 1 while the effect avocado), diet 2) low was less pronounced for saturated fat diet; diet 2. Each diet was four weeks, cross‐over design utilized. Study effects of high N=67, 30 Healthy participants (Lopez‐ MUFA diet on plasma normolipdemic and 37 showed 16% decrease Ledesma et lipids in hypercholesterolemic/ in TC for avocado diet al., 1996) normolipidemic and hypertriglyceridemic. and an increase in TC for hypercholesterolemic Dietary supplement: control diet. or Avocado enriched diet Hypercholesterolemic hypertriglyceridemic compared with participants showed patients. control diet; 7 day significant decrease of study period. 17% in TC, 22% in LDL, 22% in triglycerides, and an increase in HDL by 11% in the avocado diet and no significance in the control diet.
Avocado Consumption, Diet Quality, and Nutrient Intake
Besides its favorable effects on lipid profile in lowering CVD risk, avocado consumption has been associated with better diet quality, nutrient intake, and lower metabolic syndrome
19 risk (Fulgoni et al., 2013). In a study that was done with data collected from the National
Health and Nutrition Examination Survey (NHANES 2001‐2008), avocado consumption and nutrition data from 24‐hour dietary recalls were analyzed. There were 17,567 subjects involved, including 347 avocado consumers.
Results from the study showed that avocado‐consumers had significantly higher fruit
and vegetable intake, better diet quality, higher intake of MUFA, PUFA, dietary fiber, vitamins
E and K, Mg, and K. Diet quality was assessed using the US Department of Agriculture
(USDA) Healthy Eating Index (2005), an assessment tool that measures conformance to federal dietary guidance (Healthy Eating Index (HEI), 2013). Additionally, body weight, BMI, and waist circumference were significantly lower (Fulgoni et al., 2013). Plasma HDL levels were found to be higher for avocado consumers as well.
Data such as those provided by the described study contributes different aspects of the health benefits offered by a functional food such as the avocado, allowing dietetics professionals to provide better informed advice to clients. The cross‐sectional and observational design utilized by this study presents limitations in terms of the ability to attribute health outcomes to avocado consumption. The present study will be able to address these limitations due to its randomized and controlled parallel design.
20 Nutrient Components that are Associated with CVD Risk
Since the purpose of the present study is to address the ability of avocado supplementation to affect overall diet pattern, the following sections will be a discussion on selected food items that can contribute nutrients known to affect CVD risk.
Fruit and Vegetable Consumption
Antioxidants. Platelet activation and aggregation, caused by excessive levels of superoxide in the vascular environment, leads to thrombus formation in atherosclerosis
(Pashkow, 2011). Inhibition of the platelets by antioxidants can be indirect, via ROS scavenging or interfering with ROS metabolism. ROS scavenging by antioxidants will also help in restoring the bioavailability of nitric oxide, which can improve endothelial dysfunction in atherosclerosis. Oxidative stress can also be reduced via activating endogenous antioxidant enzyme systems such as glutathione peroxidase (Franzini et al.,
2012). It has been studied that dietary antioxidants, measured by total antioxidant capacity (TAC), is correlated with plasma antioxidant status. Therefore, consuming antioxidant‐rich foods can reduce oxidative stress and alleviate CVD risk.
Fiber. Soluble fibers from fruit and vegetables are found to lower LDL by binding to bile acids and inhibiting cholesterol synthesis (Erkkila & Lichtenstein, 2006). It has also been found to improve insulin resistance. Insoluble fibers, found mostly in cereal grains, have consistently yielded results that show benefit in lower CVD risk as well.
21 Potassium. Potassium intake has been shown by large scale studies such as the
Intersalt study, to be an independent determinant of population blood pressure (Intersalt
Cooperative Research Group, 1988). Clinical trials have shown that increasing potassium intake lowers blood pressure for hypertensive and normotensive individuals (Whelton et al.,
1997). It has been found to improve CVD risk by reducing risk of stroke and ventricular arrhythmias (He & MacGregor, 2001). Its effects on blood pressure are additive when combined with reduced sodium intake. Ideally, potassium intake should be in the form of fresh fruit and vegetables.
Table 4
Summary of Studies that Support Nutrient Components Found in Fruit and Vegetables that
Lower CVD Risk.
Objectives Methods Findings References
Investigate the N=49, hemodialysis Plasma lycopene and (Roehrs et relationships between and healthy patients. glutathione peroxidase al., 2011) plasma levels of Dependent were decreased. TC, carotenoids, tocopherols, measures: Plasma LDL, MDA, superoxide endogenous antioxidants, carotenoid, dismutase, and oxidative damage and tocopherol, and catalase were lipid profiles relative to malondialdehyde increased. Lycopene CVD risk in hemodialysis (MDA) as well as was negatively patients. erythrocyte reduced correlated with MDA, glutathione (GSH) LDL, and LDL:HDL and were measured; positively correlated plasma antioxidant with glutathione enzymes and lipid activity. profiles analyzed.
22 Table 4 continued
Objectives Methods Findings References
Examine the relationship 12 study populations Both vitamins showed (Gey & between vitamins E and analyzed. inverse relationship Puska, 1989) A with mortality for with ischemic heart ischemic heart disease. disease mortality. In combination, they showed a strong inverse relationship with ischemic heart disease mortality (r2 = 0.89‐0.94 at p<0.001). Examine if higher intake N=39,876, healthy Significant inverse (Liu et al., of dietary fiber is female health association between 2002) inversely related to the proessionals asked to dietary fiber (soluble risk of CVD and fill out food and insoluble) intake myocardial infarction frequency and CVD risk. (MI). questionnaires. 6 years duration. Dependent measures: record for incidence of MI, stroke, and other CVD events. Examine controlled trials Meta‐analysis of 67 2‐10 g/d of soluble (Brown, to quantify the controlled trials. fiber was associated Rosner, cholesterol‐lowering Regression analyses with decreases in TC Willett, & effect of major dietary used to test effect of and LDL. Triglycerides Sacks, 1999) fibers. pectin, oat bran, guar and HDL were not gum, and psyllium on significantly influenced. blood lipids.
23 Table 4 continued
Objectives Methods Findings References
Assess the effects of Meta‐analysis of 33 Potassium (Whelton et al., supplementation randomized supplementation 1997) with oral potassium controlled trials was associated with on blood pressure in (2609 participants). significant reduction humans. Potassium in men systolic and supplementation diastolic blood was the only pressure of 3.11 mm difference between Hg and 1.9 mm Hg, intervention and respectively. control. Examine the N=10,079 men and Sodium excretion (Intersalt relationship women, aged 20‐59 was positively Cooperative between electrolyte from 52 centers associated with Research Group, excretion and blood around the world. blood pressure. 1988) pressure (Intersalt Regression analyses Potassium excretion Study). were used. was negatively Urine samples associated with collected to blood pressure. measure excretion Sodium:potassium of sodium and ratio positively potassium. associated with Dependent blood pressure. measure: blood pressure Examine whether N=39,876 healthy Significant inverse (Lu et al., 2000) higher fruit and female health association between vegetable intake professionals. fruit and vegetable reduces CVD risk in Collected food‐ intake and CVD risk. a prospective frequency cohort of women questionnaires. (Women’s Health Followed for 5 years. Study). Measured nonfatal MI, stroke, other CVD events. 24
Fats. Dietary fat is a major component in determining CVD risk, as they play a role in modulating plasma cholesterol concentrations (Fernandez & West, 2005). While fish and nuts are excellent sources of PUFAs and MUFAs, other fat sources such as hydrogenated oils and animal fat can contribute to increased levels of trans and saturated fatty acids (Alissa &
Ferns, 2012). While saturated fatty acids are the single dietary component that has the greatest LDL‐cholesterol raising effect, trans fatty acids also have shown increased risk for
CVD by increasing LDL and decreasing HDL in the plasma (Alissa & Ferns, 2012). MUFA and
PUFAs have long been studied for their positive effects in modulating VLDL metabolism and reducing plasma triglycerides to lower CVD risk.
The omega‐6 and omega‐3 PUFAs are known to have modulating effects on plasma cholesterol and triglycerides (Fernandez & West, 2005). Omega‐6 modulates plasma cholesterol through a few mechanisms: 1) increasing LDL receptor mRNA and protein in the liver to increase hepatic clearance of LDL, 2) increasing CYP7 (cholesterol hydroxylase) by inducing the LXRalpha (liver x receptor) gene to increase conversion of cholesterol into bile acids for excretion, and 3) decreasing the conversion of VLDL to LDL. Omega‐3 modulates plasma triglycerides through: 1) suppressing SREBP‐1 expression that leads to decreased lipogenesis and decreased VLDL secretion, 2) increased lipoprotein lipase (LPL) activity and decreased apo C‐III levels both of which promote hepatic clearance, and 3) increasing the reverse cholesterol transport process via HDL.
25 Table 5
Summary of Studies that Examined the Effect of Fatty Acids on Lipid Profile.
Objectives Methods Findings Reference
Examine the N=59 patients with CVD. Significant decrease in (Durrington triglyceride lowering Supplement: received 2 serum triglycerides by et al., effectiveness of g/d twice a day of fish oil 20‐30% and in VLDL 2001) omega‐3 supplement supplement. Study over by 30‐40%. No from fish oil. 1 year. Dependent deleterious effect on measure: serum LDL or HDL. triglycerides and VLDL. Calculate the effect of 27 controlled trials were Predictive equations (Mensink & changes in analyzed by multiple indicate that: 1) HDL Katan, carbohydrate and fatty regression analysis using was raised when 1992) acid intake on serum isocaloric exchanges of carbohydrates were lipid ad lipoprotein SFA, MUFA, PUFA with substituted with SFA, levels in 27 controlled carbohydrates. Data MUFA, and PUFA; 2) trials. points were used to LDL was raised with create predictive SFA but lowered with equations. MUFA and PUFA; 3) triglycerides were lowered in all cases where fatty acids were substituted for carbohydrates. Examine whether 14 studies with No differences found (Gardner & MUFA or PUFA have intervention diets varied between the two. Kraemer, differential effect on in MUFA and PUFA Both lowered TC and 1995) serum lipid using meta‐ content were analyzed. LDL. analysis.
Calorie Restriction
Since weight gain and obesity has been linked with the development of CVD, studies have shown that a reduction in weight of 5% body weight can improve CVD risk in women
26 (Lindstrom & Uusitupa, 2008). Studies using the intermittent fasting strategy, where 75‐
90% of the energy needs are restricted on 1‐2 days a week, have shown reductions in LDL and triglycerides by 10% and 17%, respectively (Harvie et al, 2011). In another study with obese women, minimized intermittent fasting is combined with a daily calorie restriction of
20% reduction in total energy needs (Klempel, Kroeger, Bhutani, Trepanowski, & Varady,
2012). They found even more pronounced reductions in body weight, fat mass, visceral fat, as well as plasma LDL levels.
These studies support calorie restriction in providing benefits in lowering CVD risk.
Research on the ability of avocado consumption to increase satiety might suggest that decreased total energy consumption can yield the same cardioprotective effects on anthropometric and lipid profile as calorie‐restricted diets.
Avocado and Satiety
As mentioned previously, the ability of a food to affect satiety is an important aspect of the overall diet pattern effect that can be related to decreased total energy consumption.
Satiety is defined as “a process that leads to increased fullness after a meal, a decline in hunger, and inhibition of further eating in the postprandial period”. Avocados are nutrient‐ dense foods with properties that can affect energy balance via influencing satiety (Klempel et al., 2012). Based on the previously discussed lipid‐lowering effect of calorie‐restriction, this may be a favorable property in terms of improving CVD risk.
27 Hass avocados can affect satiety (Wein, Haddad, Oda, & Sabate, 2013). In a 3x3
single‐blind crossover study, 26 healthy overweight adults participated for 3 study days scheduled one week apart. The dietary intervention for each of those days was a test meal at lunch designed to meet recommended levels of macronutrients as developed by the
Institute of Medicine. There were three test meals for control (C), avocado‐inclusive (AI), or avocado‐added (AA). Each study day began with a standardized breakfast. At lunch, the C test meal included a salad, French baguette, and chocolate chip cookies. The AI and
AA test meals included or added sliced Hass avocados into the C test meal, respectively.
The amount of avocado ranged from 50‐90 g depending on the energy needs of the participant. Dinner on the test days was provided as a buffet meal where participants chose sweet and savory food items that were pre‐measured for portion weight, macronutrient, and calorie content. An evening snack was also offered as an option.
Their selection is then recorded for assessing postprandial food intake and dietary compensation.
Four dependent variables were measured that included satiety, dietary compensation
score, blood glucose and insulin levels. Satiety was measured by a validated tool, the
Visual Analog Scale (VAS). Dietary compensation score, the measurement of the ability of a single food to offset energy reduction at the next meal, was determined by measuring food intake at dinner and evening snack. Blood glucose and insulin levels, both of which have
28 been linked to satiety signaling, were measured using enzyme‐linked immunosorbent assay
(ELISA) and glucose‐oxidase‐peroxidase enzymatic assay.
Results from the study indicated that the addition of one half of a Hass avocado increased satiety, reduced dietary compensation, and decreased insulin levels. Satiety was determined as a 24% decreased desire to eat and 22% increased satisfaction for the AI group. Dietary compensation scores showed a reduction in 66% energy, 36% fat, 235% protein, and 118% carbohydrate at dinner and evening snacks. It should be noted that these percentages are relative to their values in the Hass avocado.
Results from this study support the ability of the avocado to reduce total energy intake
due to its effect on satiety. The fat composition, volume and weight of pulp, as well as high content of dietary fiber are all components that contribute to its ability to enhance satiety
(Ouyang, Yin, & Chen, 2006; Rolls, 2009; Jones & Schoeller, 1988; Piers, Walker, Stoney,
Soares, & O’Dea, 2002; Dreher & Davenport, 2013; Burton‐Freeman, 2000).
Food Displacement
It is important to understand the ability of a food to impact the overall diet pattern when considering its health implications. As discussed earlier, this is an aspect in the nutrition research field that is lacking and should be seriously addressed. Although studies have been done on avocado and its ability to improve CVD risk because of its effect on lipid profile, not much emphasis has been placed on its ability to affect diet pattern. Avocado
29 consumption was associated with better diet quality and nutrient intake of dietary
components that are often deficient in the diets of the US population (Fulgoni et al., 2013).
However, specific measures of its effect on displacing certain nutrients in the diet have not been studied.
Food displacement is defined by Jaceldo‐Siegl as “a measure of the degree to which the supplementation induced a change in the intake of a specific nutrient in the supplemented diet” (Jaceldo‐Siegl et al., 2004). The food displacement equation used in their study on almond‐supplementation is as follows.
Hi is the intake of a nutrient during baseline, Si is the nutrient contained in the avocado
(obtained from literature), and Ai is the intake of that nutrient during the supplemented
period. This equation determines a percentage nutrient displacement value Di.
The study on almond supplementation was able to meaningfully fulfill a gap in the large pool of literature that exists to support nut consumption in lowering CVD risk (Jaceldo‐Siegl et al., 2004). Calculating nutrient displacement values for certain nutrient components in the diet of the participants provided valuable insight on the ability of almonds to not only improve lipid profile, a notion that is widely accepted, but also favorably impact the overall diet pattern to meet the needs of several dietary guidelines that promote disease prevention.
30
Participants followed their habitual diets for the first 6 months and then added 52 g/d of almond supplement (1286 kJ) in the following 6 months. Data was obtained from seven
24‐hour recalls collected on random days over each 6 month period.
Results from the study showed that intakes of MUFA, PUFA, fiber, vegetable proein, alpha‐tocopherol, Cu, and Mg significantly increased by 42, 24, 12, 19, 66, 15, and 13%, respectively. MUFA and PUFA were displaced in the diet during almond supplementation by a value of 16 and 26%, respectively. This means that only 16% of the MUFA content found in almonds was reduced from the rest of the diet, leaving an overall increase of 84% of its value found in almonds. Displacements in total energy, total protein, total fat, SFA, total fiber, Ca, Fe, Mg, P, K, Zn and alpha‐tocopherol were approximately 54, 34, 26, 98, 29, 89, 92,
22, 43, 64, 24, and 52%, respectively. Displacement for total food weight, carbohydrate, sugars, and Se were >245%. This can be interpreted to mean that the almonds more than displaced its own value for these components, resulting in lower amounts in the supplemented diet. These results line up with guidelines that help promote cardiovascular health.
Based on the literature that we have reviewed here, we know that avocados have similar nutrient and phytochemical profiles to some tree nuts such as almonds, walnut, and pistachios, leading to similar cardiovascular health benefits as well (Dreher & Davenport,
2013). Additionally, data on food displacement values of almond supplementation show
31
that its effect on the overall diet also support cardiovascular health (Jaceldo‐Siegl et al.,
2004). Considering what we know about the favorable effects avocado consumption has on diet quality, nutrient intake, and satiety, it will be of valuable interest for the dietetics profession as well as the general public, to further examine if its effect on overall dietary pattern is similar to that of almonds (Fulgoni et al., 2013; Wein et al., 2013).
32
CHAPTER 3
METHODS
This study was done as a follow‐up to Maxwell Johnson’s study on “The effect of regular
avocado feedings on the serum lipids and body composition of healthy, free‐living students” conducted at the California State Polytechnic University, Pomona in 2012 (Johnson, 2012).
Results from the present study is meant to build on his previous findings. Therefore, subsequent sections in this chapter will outline the methodology that was used in the primary study. Some data that was obtained in that study was used for the purposes of the present study. These data will be discussed as well.
Participants
Participants selected for the primary study were all students attending California State
Polytechnic University, Pomona. The study was conducted to examine the effects of avocado consumption on serum lipid profile and body composition of free‐living and healthy individuals. The study and all forms used were approved by the California State Polytechnic
University, Pomona Institutional Review Board under Protocol 11‐136. The approval letter is included in Appendix A. Recruitment was done on the school campus over flyers and emails. Consent forms and study questionnaires were utilized in the screening and selection process to determine if they are eligible for participation in the study.
33
The exclusion criteria for the study are as follows: younger than 18, older than 40, had a preexisting chronic disease with the exception of high blood cholesterol, had a recently altered diet or exercise pattern, consumed avocados daily as normal routine, currently on antibiotics, steroid, o cholesterol‐lowering medication, were pregnant or had been in the last 12 months, or were on hormonal medications with the exception of birth control.
The inclusion criteria are as follows: between the ages of 18 and 40, free from chronic disease with the exception of high blood cholesterol, had stable diet and exercise pattern, were open to eating avocados daily, were not on antibiotic, steroid, or cholesterol‐lowering medication, were not pregnant and had not been for the previous 12 months, and were not on hormonal medications with the exception of birth control.
Participant records were stored in folders labeled only with participant ID in a locked
file container at the Principal Investigator’s house.
Experimental Design
26 participants, between the ages of 18‐40, were included in the study. The study was a parallel design with two dietary interventions: 1) avocado‐free control and 2) avocado‐ enriched. Participants were randomly assigned to each of the two interventions, making sure that equal numbers of each gender were in each group.
All 26 participants began with a four‐week avocado‐free run‐in period followed by an eight‐week dietary intervention period in which they were randomly assigned to either the
34
control or avocado‐enriched group. For the purposes of the present study, only the data from those participants assigned to the avocado‐enriched treatment group will be included.
Since all participants were put on a 4‐week avocado‐free run in period, the included participants will serve as their own control.
Dietary Treatment
Participants were asked to complete a consent form that included information on the dietary and health implications as well as inclusion and exclusion criteria. The screening questionnaire was completed after the consent form to assess the participant’s background on diet and exercise routine. Participants were also asked to maintain normal diet and exercise routine for the duration of the study, the only exception being avocados for the avocado‐enriched dietary intervention group. Changes in dietary and exercise patterns, as well as dietary adherence, were assessed with 24‐hour recalls and an unusual diet diary.
Avocados that were used in this study were provided by Index and Fresh and picked up
at the distribution facility in Colton, CA by study personnel. All avocados were Hass variety, grown in Chile, size #70, and obtained in an unripe condition. Each avocado contained approximately 5 oz of pulp. They were ripened in a dark room at approximately 22 degrees
Celsius in their shipping containers. Ripened avocados, assessed by finger pressing, were stored in a refrigerator at 2 degrees Celsius for participant pick‐up on a weekly basis. All participants consumed avocados that were similar in ripeness to maintain consistency.
35
The avocado‐free diet, utilized by all participants in the four‐week run‐in and those assigned to the control diet during the eight‐week treatment period, requires participants to maintain normal dietary and exercise patterns while avoiding ingestion of any avocado or avocado‐derived products.
The avocado‐enriched diet was utilized by the avocado‐enriched treatment group
during the eight‐week treatment period. Normal diet and exercise patterns were required of the participants while consuming 5 oz of avocado a day. They were instructed to avoid ingesting other sources of avocado, and were encouraged to incorporate it rather than add it into their diet.
Data Collection
The Cal Poly Avocado study procedure included anthropometric data collection, blood sampling and handling details as well as 24‐hour diet recalls. We will only discuss the blood sampling and 24‐hour diet recall collection methods as they pertain to this study.
Blood Sampling
Blood samples were collected at weeks 0, 4, and 12. Trained phlebotomists at the
Student Health Center on the California State Polytechnic University, Pomona campus carried out blood draws on participants. A 12‐hour fast was instructed prior to the blood draw to ensure serum lipids were stabilized. Collected blood samples were centrifuged and refrigerated to await pick‐up for lipid analysis by Quest Diagnostics.
36
24‐Hour Diet Recall
One recall was completed by participants during the run‐in period and three more during the treatment period. The days on which these recalls were collected were randomly chosen. Emails were sent out to the participants with an attached 24‐hour recall worksheet, as included in Appendix II. The digital copies were stored in study personnel’s computers and then printed out to be included with other participant data. The recall data, initially meant for adherence assessment, were not used due to budgetary constraints.
Nutrient Component Analysis
A nutrient component analysis was conducted by the primary study personnel using
data collected from the 24‐hour diet recalls. Nutrient analyses were generated using ESHA software. The analyses provided nutrient composition values in the diets of the 26 participants. Only a selection nutrients from the nutrient component analysis was included for the present study based on relevance to the study purpose.
Adherence Assessment
An unusual diet diary was kept by all participants detailing any deviations from dietary or exercise pattern as specified for the purposes of the study. Deviations include prohibited avocado consumption, failure to consume avocados as assigned by dietary treatment, binging or fasting, excessive exercise or lack thereof, or use of medication that was not reported at the beginning of the study.
37
Data Analysis
Selection of Nutrients of Interest
The nutrient components selected for the purpose of this study is listed in Table 6.
Table 6
Nutrient Components Analyzed for this Study.
Food weight (g) Chol (mg) Vit E‐a‐Toco (mg) Omega3 (g) Cals (kcal) Water (g) Folate (mcg) Omega6 (g) FatCals (kcal) Vit A‐RAE (RAE) Vit K (mcg) Alc (g) SatCals (kcal) Caroten (RE) Panto (mg) Caff (mg) Prot (g) Retinol (RE) Calc (mg) Chln (mg) Carb (g) BetaCaro (mcg) Copp (mg) Fib (g) Vit B1 (mg) Iron (mg) SolFib (g) Vit B2 (mg) Magn (mg) Sugar (g) Vit B3 (mg) Mang (mg) Fat (g) Vit B6 (mg) Phos (mg) SatFat (g) Vit B12 (mcg) Pot (mg) MonoFat (g) Vit C (mg) Sel (mcg) PolyFat (g) Vit D‐IU (IU) Sod (mg) TransFat (g) Vit D‐mcg (mcg) Zinc (mg)
These nutrients were selected based on the existing literature reviewed that supports their roles in affecting CVD risk. Since nutrient displacement calculations are based on the nutrient’s value in the avocado, not all of the listed nutrients can be included for the displacement analysis. For example, since “alcohol (Alc)” and “Caff (caffeine)” are not found in avocados, displacement won’t be calculated and only an absolute change value will be determined.
38
For convenient referencing between results and data analytical methods, the following sections will be organized according to the objectives of the study.
Analysis for Objective 1: Nutrient Profile
A nutrient profile on the nutrient components listed in Table 6 was analyzed for changes in diet composition. Values for each nutrient component during run‐in (R) and the avocado‐supplemented (A) period were obtained. Percentage differences, calculated by (A
– R)/R x 100, allowed us to evaluate changes in nutrient composition of the participants’
diets between the run‐in and supplemented period.
Analysis Objective 2: Nutrient Displacement
Nutrient displacement calculations were done for the nutrients listed in Table 6 with the exception of trans fat, cholesterol, retinol, vitamin B12, vitamin D, alcohol, and caffeine.
Values for these nutrients were listed for the run‐in and avocado‐supplemented period. To calculate nutrient displacement percentage, the displacement equation developed by a previous study that examined food displacement was used (Jaceldo‐Siegl, 2004). The equation adapted to the present study is [(S + R – A)/S] x 100, where R=nutrient value from run‐in period, A=nutrient value from avocado‐supplemented period, and S=nutrient value in the supplemented 5 oz Hass avocado. The nutrient values for the avocado supplement was obtained from the USDA National Nutrient Database (USDA, 2011). All individual values were presented in the table along with calculated values. Nutrient displacement
39 percentages determined the degree to which a specific nutrient was displaced by the
avocado supplement in the supplemented diet of the participants.
Analysis Objective 3: Associations between Nutrient Changes and Lipid Profile
Findings from the Cal Poly Avocado study found that non‐HDL to HDL cholesterol ratio increased in the control group but didn’t in the avocado‐enriched treatment group (Johnson,
2012). Furthermore, the avocado‐enriched group showed increases in mean cholesterol ratio during the run‐in period and a slowed decline over the treatment period.
Since LDL, HDL, and TC values were analyzed by Quest Diagnostics for the Cal Poly
Avocado study, these values were analyzed for association with nutrient displacement and intake changes of certain nutrients as stated in the hypotheses. Since lipid ratios are used for CVD risk indicators, ratios of LDL:HDL or TC:HDL were calculated as lipid profile components for analysis as well. The lipid profile values were from blood samples collected on week 4 and 12, prior to and post treatment period, respectively. The values for lipid profile components were plotted against nutrient displacement percentages in a bivariate scatterplot. Relationship between nutrient displacement and plasma lipid components were examined using regression analysis since we are testing if plasma lipid changes is a function of specific nutrient displacement.
40 Statistical Methods
Out of the 26 participants that were selected for the primary study, 13 were included for the present study. Mean values for each nutrient component among the 13 participants are calculated and presented for each nutrient value in nutrient profile and nutrient displacement analyses. Respective standard deviation (SD) and standard error of the mean (SEM) values were calculated. Due to the nature of the study, the paired sample
Wilcoxon signed ranking test was used to determine the significance (p‐value) of the differences between nutrient values from the run‐in and avocado‐supplemented period.
For displacement values, the same statistical method was used to test the null hypothesis that displacement equals zero. Since multiple hypotheses are being tested on the same data set, the Bonferroni adjustment method is utilized where the new critical level for determining significance was 0.001 for both diet composition and nutrient displacement data. For examining relationships between lipid profile components and nutrient displacement, individual values were used to create a bivariate scatterplot for regression analysis. The p‐value determined for the regression analysis tests the null hypothesis that the regression coefficient is equal to zero, i.e. plasma lipid does not change as nutrient displacement changes. The statistical analyses were performed using Prism GraphPad 6.0 software for Windows statistical software package (Motulsky, 2014).
41
CHAPTER 4
RESULTS
Primary study results included an analysis of participant characteristics as well as
baseline plasma lipids and found that there were no significant group differences among them (Johnson, 2012). Tables detailing the characteristics that were analyzed by the primary study personnel are included in Appendix C. Percent adherence was also calculated by using the unusual diet diaries for the primary study. This was calculated to be
99.0% + 0.02% for the run‐in diet, 98.4% + 0.03% for the treatment phase, 99.5% + 0.01% for the avocado‐free control group, and 97.3% + 0.05% for the avocado‐enriched group.
Hypothesis 1
Hypothesis 1 states that total calories consumed, monounsaturated and polyunsaturated fat, fiber, and antioxidant vitamin and minerals will be significantly greater in the avocado‐supplementation period than in the avocado‐free period. Percent changes in mean values of the above‐mentioned diet components are presented in Table 7.
Although total calories increased by 1.85%, MUFA increased by 150%, PUFA increased by
79.8%, soluble fiber increased by 6.48%, retinol increased by 29.3%, and selenium increased by 76.4%, the other components stated in the hypothesis showed decreases. Total fiber decreased by 12.0%, vitamin A decreased by 7.15%, carotene decreased by 15.5%, beta‐ carotene decreased by 8.10%, vitamin C decreased by 8.34%, vitamin E decreased by
42 25.56%, and iron decreased by 14.35%. No significance was determined by the Wilcoxon
signed ranking test. Therefore,the data does not support hypothesis 1.
Hypothesis 2
Hypothesis 2 states that carbohydrates, cholesterol, saturated and trans fats will be significantly lower in the avocado‐supplementation period than in the avocado‐free period.
Table 7 shows us that carbohydrates and trans fat decreased by 22.07% and 19.87%, respectively. However, saturated fat and cholesterol were increased by 33.87% and
36.70%, respectively. The data was not significant, and the increases in saturated fat and cholesterol does not support hypothesis 2.
43 Table 7
Mean Diet Compositional Changes of Participants between the Two Study Periods.
Avocado‐ Run‐in period (H) (A‐H) % ((A‐H)/H x 100) supplemented period mean SD mean SD mean SEM % p‐value* Wgt (g) 2197.11 709.63 2131.30 762.17 ‐65.81 172.16 ‐3.00 0.74 Cals (kcal) 2539.28 962.13 2586.26 1525.18 46.98 491.48 1.85 0.64 FatCals (kcal) 838.57 404.08 1150.17 1138.13 311.60 340.00 37.16 0.64 SatCals (kcal) 245.19 131.61 328.23 339.18 83.04 91.92 33.87 0.59 Prot (g) 90.19 49.63 100.73 89.53 10.54 27.10 11.68 >0.999 Carb (g) 344.25 167.76 268.27 85.43 ‐75.97 55.44 ‐22.07 0.45 Fib (g) 31.24 30.07 27.49 7.70 ‐3.76 8.62 ‐12.03 0.95 SolFib (g) 0.93 1.13 0.99 0.78 0.06 0.37 6.48 0.64 Sugar (g) 107.04 63.22 93.13 43.48 ‐13.91 18.43 ‐13.00 0.59 Fat (g) 93.33 45.03 127.98 126.53 34.65 37.84 37.13 0.64 SatFat (g) 27.24 14.62 36.47 37.69 9.23 10.21 33.87 0.59 MonoFat (g) 14.23 15.16 35.61 45.42 21.38 14.75 150.28 0.31 PolyFat (g) 5.73 5.76 10.30 13.00 4.57 4.36 79.84 0.50 TransFat (g) 1.44 2.53 1.15 0.95 ‐0.29 0.81 ‐19.87 0.59 Chol (mg) 245.23 161.76 335.23 429.70 90.00 118.20 36.70 0.95 Water (g) 1273.95 611.85 1209.85 712.46 ‐64.10 212.73 ‐5.03 0.38 Vit A‐RAE (RAE) 379.10 643.16 351.98 284.79 ‐27.12 181.78 ‐7.15 0.74 Caroten (RE) 616.69 1264.74 521.01 630.90 ‐95.68 349.79 ‐15.51 0.64 Retinol (RE) 70.76 90.21 91.47 93.74 20.71 41.80 29.27 0.74 BetaCaro (mcg) 3012.20 6247.96 2768.31 3484.22 ‐243.89 1799.81 ‐8.10 0.59 Vit B1 (mg) 0.92 0.99 1.52 1.79 0.60 0.63 64.56 0.41 Vit B2 (mg) 0.95 1.00 2.03 2.33 1.07 0.80 112.48 0.24 Vit B3 (mg) 14.26 18.54 20.09 26.25 5.83 9.68 40.87 0.41 Vit B6 (mg) 1.24 1.46 2.10 2.48 0.86 0.87 69.56 0.24 Vit B12 (mcg) 3.25 5.71 3.70 3.54 0.45 1.92 13.96 0.50 Vit C (mg) 128.09 113.11 117.41 119.75 ‐10.68 51.27 ‐8.34 0.45 Vit D‐IU (IU) 40.75 74.28 152.64 369.01 111.89 107.25 274.56 0.27 Vit D‐mcg (mcg) 1.01 1.85 3.79 9.22 2.78 2.68 276.36 0.27 Vit E‐a‐Toco (mg) 6.59 8.36 4.91 3.04 ‐1.68 2.31 ‐25.56 0.89 Folate (mcg) 244.32 277.74 288.62 73.66 44.30 79.81 18.13 0.19 Vit K (mcg) 55.04 126.06 60.51 77.04 5.48 38.21 9.95 0.50 Panto (mg) 2.95 3.74 4.47 3.73 1.52 1.69 51.72 0.41 Calc (mg) 641.03 382.00 682.59 408.44 41.56 93.26 6.48 0.68 Copp (mg) 0.76 0.63 1.00 0.52 0.23 0.25 30.55 0.41 Iron (mg) 16.72 10.45 14.32 7.49 ‐2.40 3.41 ‐14.35 0.34 Magn (mg) 151.47 157.22 183.10 88.65 31.62 46.55 20.88 0.54 Mang (mg) 2.25 2.83 2.00 0.77 ‐0.26 0.71 ‐11.43 0.79 Phos (mg) 553.93 618.71 734.88 673.68 180.95 270.98 32.67 0.45 Pot (mg) 1380.85 1296.92 2054.48 1372.24 673.63 589.21 48.78 0.27 Sel (mcg) 43.74 72.42 77.16 127.83 33.43 42.98 76.43 0.38 Sod (mg) 3652.21 1293.25 3029.01 1371.74 ‐623.21 450.05 ‐17.06 0.24 Zinc (mg) 9.17 14.04 10.87 15.05 1.70 6.25 18.51 0.54 Omega3 (g) 0.36 0.35 0.56 0.59 0.20 0.22 55.25 0.54 Omega6 (g) 4.00 4.39 8.16 12.28 4.15 3.88 103.68 0.59 Alc (g) 2.45 5.92 1.72 4.15 ‐0.73 2.17 ‐29.94 >0.999 Caff (mg) 25.29 71.14 21.17 38.39 ‐4.13 22.39 ‐16.31 0.55 Chln (mg) 88.84 159.12 158.33 310.76 69.49 102.11 78.21 0.19
Note: *Wilcoxon signed ranking test used; significance is determined at 0.05/47 = 0.001.
44 Hypothesis 3
Hypothesis 3 states that displacement of monounsaturated and polyunsaturated fat, fiber, and antioxidant vitamin and minerals in the avocado‐supplementation period relative to the avocado‐free period will be < 100%. Table 8 shows that MUFA was displaced by ‐
53.6 %, PUFA by ‐77.0%, and soluble fiber by 97.9%. Total fiber was displaced by 139%,
vitamin A by 373%, carotene by 555%, beta‐carotene by 373%, vitamin C by 185%, vitamin E by 160%, and iron by 377%. The insignificant values do not support hypothesis 3.
Hypothesis 4
Hypothesis 4 states that the displacement of carbohydrate and saturated fat in the
avocado‐supplementation period relative to the avocado‐free period will be >100%. Table
8 shows that carbohydrates were displaced by 719% while saturated fat was displaced by ‐
205%. The values were non‐significant, and do not support hypothesis 4.
45 Table 8
Mean Nutrient Displacement Values.
Avocado Nutrient Habitual Avocado diet Absolute (D) % displacement supplement H A S S+H‐A D/S * 100 SEM p value* Wgt (g) 2197.11 2131.30 142.00 207.81 146.34 121.24 0.31 Cals (kcal) 2539.28 2586.26 237.14 190.16 80.19 207.25 0.68 FatCals (kcal) 838.57 1150.17 196.81 ‐114.79 ‐58.32 172.75 0.79 SatCals (kcal) 245.19 328.23 27.22 ‐55.82 ‐205.06 337.67 0.95 Prot (g) 90.19 100.73 2.78 ‐7.75 ‐278.59 973.53 0.95 Carb (g) 344.25 268.27 12.27 88.24 719.22 451.90 0.24 Fib (g) 31.24 27.49 9.66 13.41 138.91 89.23 0.17 SolFib (g) 0.93 0.99 2.90 2.84 97.92 12.70 0.0002 Sugar (g) 107.04 93.13 0.43 14.34 3365.86 4326.87 0.59 Fat (g) 93.33 127.98 21.87 ‐12.78 ‐58.45 173.04 0.79 SatFat (g) 27.24 36.47 3.02 ‐6.20 ‐205.05 337.68 0.95 MonoFat (g) 14.23 35.61 13.92 ‐7.47 ‐53.65 106.00 0.95 PolyFat (g) 5.73 10.30 2.58 ‐1.99 ‐76.95 168.70 0.74 Water (g) 1273.95 1209.85 102.67 166.76 162.43 207.21 0.38 Vit A‐RAE (RAE) 379.10 351.98 9.94 37.06 372.88 1828.82 0.79 Caroten (RE) 616.69 521.01 21.02 116.69 555.26 1664.38 0.95 BetaCaro (mcg) 3012.20 2768.31 89.46 333.35 372.62 2011.86 0.84 Vit B1 (mg) 0.92 1.52 0.11 ‐0.48 ‐424.56 553.73 0.68 Vit B2 (mg) 0.95 2.03 0.20 ‐0.87 ‐439.26 402.53 0.49 Vit B3 (mg) 14.26 20.09 2.71 ‐3.12 ‐114.95 356.81 0.45 Vit B6 (mg) 1.24 2.10 0.41 ‐0.45 ‐109.46 211.12 0.84 Vit C (mg) 128.09 117.41 12.50 23.18 185.47 410.32 0.34 Vit E‐a‐Toco (mg) 6.59 4.91 2.80 4.48 160.22 82.49 0.04 Folate (mcg) 244.32 288.62 126.38 82.08 64.95 63.15 0.74 Vit K (mcg) 55.04 60.51 29.82 24.34 81.63 128.12 0.31 Panto (mg) 2.95 4.47 2.07 0.55 26.52 81.55 0.74 Calc (mg) 641.03 682.59 18.46 ‐23.10 ‐125.15 505.18 0.74 Copp (mg) 0.76 1.00 0.24 0.01 3.24 104.60 > 0.9999 Iron (mg) 16.72 14.32 0.87 3.26 376.89 393.42 0.24 Magn (mg) 151.47 183.10 41.18 9.56 23.21 113.04 0.84 Mang (mg) 2.25 2.00 0.21 0.47 220.98 333.71 > 0.9999 Phos (mg) 553.93 734.88 76.68 ‐104.27 ‐135.98 353.39 0.84 Pot (mg) 1380.85 2054.48 719.94 46.31 6.43 81.84 0.68 Sel (mcg) 43.74 77.16 0.57 ‐32.86 ‐5785.11 7567.64 0.38 Sod (mg) 3652.21 3029.01 11.36 634.57 5585.97 3961.68 0.24 Zinc (mg) 9.17 10.87 0.97 ‐0.73 ‐75.75 647.26 0.79 Omega3 (g) 0.36 0.56 0.22 0.02 8.66 99.83 0.41 Omega6 (g) 4.00 8.16 2.95 ‐1.20 ‐40.55 131.24 0.38 Chln (mg) 88.84 158.33 36.35 ‐33.13 ‐91.15 280.89 0.89 Note: * Wilcoxon signed ranking test used because of small sample and lack of normality in distribution; The values are tested against the H0 of 0% displacement.**To control for number of variables measured, significance is determined at 0.05/39 = 0.001.
46 Hypothesis 5
Hypothesis 5 states that the displacement of monounsaturated fat will be positively associated with change in plasma TC, LDL, and TC:HDL. Table 9 shows that there is a positive slope determined by regression analysis. However, since the values were insignificant, hypothesis 5 was not supported.
Hypothesis 6
Hypothesis 6 states that the displacement of fiber will be positively associated with change in plasma TC, LDL, and TC:HDL. Table 9 shows that there is a positive slope value for TC and TC:HDL when regressed on % fiber displacement, and a negative slope for LDL on % fiber displacement. These values were non‐significant, therefore hypothesis 6 was not supported.
Hypothesis 7
Hypothesis 7 states that the displacement of PUFA will be positively associated with change in plasma LDL and LDL:HDL ratios. Table 9 shows that there is a positive slope determined by regression analysis for LDL and LDL:HDL against % PUFA displacement.
However the values were non‐significant, therefore they did not support hypothesis 7.
Hypothesis 8
Hypothesis 8 states that the displacement of antioxidants will be positively associated
with change in plasma LDL and LDL:HDL ratios. Table 9 shows that there is a positive slope
47 determined for both LDL and LDL:HDL ratios when regressed on the antioxidants vitamin A,
carotene, beta‐carotene, vitamin E, iron, and selenium. However vitamin C shows a negative slope for LDL:HDL and positive slope for LDL. All values were non‐significant, therefore hypothesis 8 was not supported.
Hypothesis 9
Hypothesis 9 states that the displacement of carbohydrate will be positively associated with change in HDL and negatively associated with change in TC:HDL ratio. Table 9 shows that there is a positive slope determined between carbohydrate and HDL and a negative slope between carbohydrate and TC:HDL. However, due to non‐significant values, hypothesis 9 was not supported.
Hypothesis 10
Hypothesis 10 states that the change in trans fat intake will be positively associated with change in HDL and negatively associated with change in TC:HDL ratio. Table 9 shows a positive slope between trans fat intake and HDL and a negative slope between trans fat and
TC:HDL. Due to insignificant values, hypothesis 10 was not supported.
48 Hypothesis 11
Hypothesis 11 states that change in dietary cholesterol intake will be positively associated with change in plasma HDL. Table 9 shows that there is a negative slope value between dietary cholesterol intake and plasma HDL, determined to be insignificant.
Therefore, hypothesis 11 was not supported.
Hypothesis 12
Hypothesis 12 states that displacement of total calories, carbohydrate, and saturated fat will be negatively associated with change in plasma total cholesterol and LDL. Table 9 shows that negative slope values were determined between total calorie displacement and
LDL, carbohydrate displacement and TC, carbohydrate displacement and LDL, and saturated fat displacement and LDL. However positive slope values were determined for total calorie displacement and TC and saturated fat displacement and TC. These results were determined to be insignificant, therefore hypothesis 12 was not supported.
49 Table 9
Associations between Nutrient Displacement or Intake and Plasma Lipids.
Nutrient % displacement or Change in plasma lipid Regression coeffecient* p‐value nutrient intake
TC 0.004944 ± 0.009006 0.59 Hypothesis 6 MUFA % displacement vs TC:HDL 0.004296 ± 0.002926 0.55 LDL 0.004279 ± 0.006994 0.17 TC 0.003152 ± 0.01080 0.78 Hypothesis 7 Fiber % displacement vs LDL -0.003473 ± 0.008384 0.69 TC:HDL 0.002874 ± 0.003691 0.45 LDL 0.002508 ± 0.004404 0.58 Hypothesis 8 PUFA % displacement vs LDL:HDL 0.003374 ± 0.001853 0.10 LDL 0.0001908 ± 0.0004082 0.65 Vitamin A % displacement vs LDL:HDL 4.094e-005 ± 0.0001952 0.84
LDL 4.266e-005 ± 0.0004528 0.93 Carotene % displacement vs LDL:HDL 8.986e-005 ± 0.0002127 0.68 Beta‐carotene % LDL 8.274e-008 ± 0.0003747 1.00 vs displacement LDL:HDL 8.378e-005 ± 0.0001755 0.64
LDL 0.0009603 ± 0.001814 0.61 Hypothesis 9 Vitamin C % displacement vs LDL:HDL -0.0009290 ± 0.0008255 0.29 LDL 0.01656 ± 0.007654 0.05 Vitamin E % displacement vs LDL:HDL 0.01161 ± 0.006290 0.09 LDL 0.001719 ± 0.001845 0.37 Iron % displacement vs LDL:HDL 0.0006859 ± 0.0008816 0.45 LDL 5.802e-005 ± 9.807e-005 0.57 Selenium % displacement vs LDL:HDL 5.614e-005 ± 4.373e-005 0.23 Carbohydrate % HDL 0.0003935 ± 0.001589 0.81 Hypothesis 10 vs displacement TC:HDL -0.0001090 ± 0.0007499 0.89 HDL 0.1043 ± 0.8904 0.91 Hypothesis 11 Trans fat intake vs TC:HDL -0.5352 ± 0.3847 0.19 Hypothesis 12 Dietary cholesterol intake vs HDL -0.003683 ± 0.004007 0.38 Total calories % TC 0.0002635 ± 0.004668 0.96 vs displacement LDL -0.0007920 ± 0.003630 0.83
Carbohydrate % TC -0.0006125 ± 0.002133 0.78 Hypothesis 13 vs displacement LDL -0.0007340 ± 0.001653 0.67 Saturated fat % TC 0.0009267 ± 0.002852 0.75 vs displacement LDL -0.0001370 ± 0.002232 0.95 Note: *Regression analysis was used, the slope is calculated to measure the degree to which y is a function of x (e.g. plasma lipid changes is a function of nutrient displacement).
50
CHAPTER 5
DISCUSSION
The aim of the present study was to examine the effect of avocado consumption on the overall diet through looking at changes in diet composition, nutrient displacement, and the relationship between nutrient displacement and changes in plasma lipids. Although insignificant values were obtained for almost all nutrient components with the exception of soluble fiber in nutrient displacement, each analyses was still discussed in comparison to literature and in terms of CVD risk to explore potential for future studies with improved statistical power. Despite the insignificance of the results, values for some diet composition, nutrient displacement and some associations between nutrient displacement and lipid profile changes were found to be congruent with existing literature.
Diet Composition
The effect of avocado consumption on diet composition was analyzed looking at the nutrient profile of the participants’ diets during run‐in and supplemented periods. Based on existing research data that supports the ability of avocado consumption to improve diet quality and nutrient intake of some shortfall nutrients, it became an interest for the present study to look at whether dietary composition of certain nutrients was changed in favor of improving CVD risk (Fulgoni et al., 2013). The primary diet components of interest were total calories, MUFA, PUFA, fiber, antioxidant vitamin and minerals, carbohydrates,
51 cholesterol, saturated fat and trans fat. These nutrient components were originally
selected based on existing literature support for their ability to improve CVD risk (Wein et al., 2013; Erkkila & Lichtenstein, 2006). As was mentioned previously, although results for diet composition are determined to be insignificant, the values will still be discussed to explore the potential for cardiovascular benefits as a basis for future research.
Results indicated that there were increases in total calories, MUFA, PUFA, soluble fiber, retinol, and selenium. Total fiber, vitamin A, carotene, beta‐carotene, vitamin C, vitamin E, and iron were decreased. MUFA and PUFA had the greatest increases by 150% and 79.8%, respectively. This is in accordance with data obtained from NHANES, where they found avocado consumers to have higher intake of MUFA (by 18 %) and PUFA (by 12%) as compared with non‐avocado consumers (Fulgoni et al., 2013). Since MUFA and PUFA have been shown to improve CVD risk, the significant increases in these components show cardioprotective potential (Durrington et al., 2001; Mensink & Katan, 1992; Gardner &
Kraemer, 1995). Similarly, total calories was also higher for avocado‐consumers compared to non‐consumers. We found that participants also had increases in total calories by 1.85% after being supplemented with avocados. This is understandable since the avocado contains approximately 230 kcal per 136 g fruit, approximately 2% of 2000 kcal diet (Dreher
& Davenport, 2013). Fiber and antioxidants are known for their ability to improve lipid
profile and reduce oxidative stress, important in lowering CVD risk (Roehrs et al., 2011; Gey
52 & Puska, 1989; Liu et al., 2002; Brown et al., 1999; Lu et al., 2000). Since avocados contain
significant sources of dietary fiber, vitamin A, vitamin C, and vitamin E, it was hypothesized that these components would be increased in the supplemented diet (Dreher & Davenport,
2013). However, since they were all found to have decreased, perhaps a reason for this is that they were displaced by avocado consumption. Fiber was consumed at an average of
31g and 27 g at run‐in and treatment. Compared to the DRI levels of 25 g/d for women and 38g/d for men, these levels are not drastically inadequate (IOM, 1997a). Vitamin C, despite a decrease, was still above the DRI whereas vitamins A and E were below the recommended levels throughout both periods (IOM 1997b). Although total fiber content decreased, the soluble component was increased. Some studies show a decrease in total cholesterol and LDL from soluble fiber intake (Brown et al., 1999).
Carbohydrates and trans fats were decreased by 22% and 20% whereas saturated fat and cholesterol were increased by 34% and 36% in the supplemented diet. The ability of simple carbohydrates, trans fats, saturated fat, and cholesterol to raise CVD risk through modification of plasma lipids and susceptibility to developing risk factors (e.g. high blood glucose, obesity, hypertension, etc.) is well documented (Aller, Abete, Astrup, Martinez, & van Baak, 2011; Alissa & Ferns, 2012; Mensink & Katan, 1992). NHANES data indicated that avocado‐consumers were more likely to consume less carbohydrate and meats, a significant source of some saturated fat, but greater discretionary fat in the form of oils and solid. The
53 data obtained in the present study partially supports NHANES results in showing decreased
carbohydrate consumption. Although trans fat consumption was significantly decreased, increases in saturated fat and cholesterol may not indicate improvement in CVD risk.
Participants were advised to incorporate the avocado supplement into their diets for the study period, and were provided recipes for ideas (Johnson, 2012). Since the mean total energy increase was only 1.85%, and total food weight was decreased by approximately
3%, this indicates that the avocado supplement was most likely incorporated rather than simply added into the diet of the participants. In a study done on avocado and satiety, it was observed that including an avocado (e.g. iso‐caloric to the control diet) in a diet yields similar results to adding an avocado to the diet (Wein et al., 2013). Increased satisfaction and a reduced desire to eat were observed for both. It was also suggested that increased calorie intake, fat, and fiber components in the avocado diets may contribute to feelings of fullness (Burton‐Freeman, 2000). Although the supplemented diets showed an increase in total energy intake, the average increase was only approximately 47 kcal. In the context of a standard 2000 kcal diet, this may not be a significant difference in diet composition.
Taken together, the minimal energy increase, decrease in total food weight, decrease in carbohydrate and total fiber intake may be partly explained by increased satiety promoted by participants including the avocado in the meals (Burton‐Freeman, 2000).
54 The ability of avocados to affect the overall diet composition is similar to that of
almonds as they both show potential to reduce CVD risk (Jaceldo‐Siegl et al., 2004). Tree nuts such as almonds have been compared to avocados for their similarities in nutrient profile and cardioprotective properties (Dreher & Davenport, 2013). Significant increases in intake of MUFA and PUFA are similar to that in the avocado supplemented diet of the present study (Jaceldo‐Siegl et al., 2004). Additionally, decreases were observed in both avocado and almond‐supplemented diets for total cholesterol and trans fat. Other similarities include reductions in sodium and sugars. Both items are associated with increased CVD risk factors (Intersalt Cooperative Research Group, 1988; Aller et al., 2011).
It was suggested by the researchers that individuals on the supplemented diet may have regarded the almond supplementation as healthy and felt less need to supplement, resulting in the decreases in vitamins A, C, and E, as well as Ca, Se, and Zn (Jaceldo‐Siegl et al., 2004).
The same explanation might be applied to the avocado consumers in the present study, where intake of vitamins A, C, and E were also reduced during supplementation.
Although there are dietary component changes detrimental to cardiovascular health
observed in the diet composition of the participants, there are also changes that are in favor of lowered CVD risk. The large increase in powerful cardioprotective components such as
MUFA and PUFA provided by avocado supplementation should be a reason to support its role in lowering CVD risk. Although B vitamins are less emphasized by literary research for
55 CVD risk, they have been found to lower homocysteine levels (Lutsey et al., 2006).
Therefore, their amounts within or above DRI levels may also contribute to lowering CVD risk
(IOM, 1998). Increased vitamin D also supports cardiovascular health as it is known to be involved in several signaling systems for cardiac function (Bae et al., 1985). Although the effect of caffeine on cardiovascular health is still controversial, alcohol intake has been associated with several cardiovascular events (Frishman, Del Vecchio, Sanal, & Ismail, 2003).
Reduced intake of both can only improve CVD risk. Table 10 provides a summary of the dietary composition changes that are in favor of lowering CVD risk and those that are not.
Table 10
Summary for Diet Compositional Changes that Lower and Raise CVD Risk.
Components that reduce CVD risk Components that increase CVD risk Reduced food weight Increased fat Reduced carbohydrate Increased saturated fat Increased soluble fiber Reduced total fiber Reduced sugar Increased total cholesterol Decreased vitamin A, carotene, beta‐ Increased MUFA carotene Increased PUFA (omega 3 and omega 6) Reduced vitamin C Reduced trans fat Reduced vitamin E Increased retinol Reduced iron Increased B vitamins Reduced sodium Increased vitamin D Increased magnesium Increased potassium Increased selenium Reduced alcohol and caffeine
56
Nutrient Displacement
Nutrient displacement describes the degree to which the nutrient intake from the rest of the diet (not including avocado) was changed due to the avocado supplementation. All results analyzed for nutrient displacement was non‐significant with the exception of soluble fiber (p‐value 0.0002). The non‐significance may be due to inadequate sample size, therefore future studies might consider including more participants to improve statistical power of the study. In the preceding paragraphs, displacement values will be discussed regardless of insignificance to explore the results in comparison with literature.
With a displacement value of ‐54% and ‐77%, not only was there no displacement of
MUFA and PUFA by avocado, there were additional amounts of these nutrients contributed to the supplemented diet from other foods. This additional contribution is measured relative to the supplement, in this case 54% of the MUFA and 77% of the PUFA found in avocado. It can be suggested that consuming avocados might have increased the intake of other MUFA and PUFA‐rich foods such as fish, nuts and oils (Alissa & Ferns, 2012). For example, in salads where avocados are often added, other MUFA‐rich ingredients such as olive oil and some nuts will also be more likely to be incorporated. In this way avocado consumption could be said to help encourage MUFA and PUFA intake from other food sources that are cardioprotective. On the other hand, total fiber was displaced by more than its amount, at 139%, indicating that the reduction of fiber intake from the rest of the
57 diet exceeded the fiber content in avocados by 39%. Other displacements of greater than
100% were observed for the antioxidants vitamins A, C, E, and iron, indicating that these amounts were displaced by more than the amounts provided by the avocado. Since these levels were below DRI levels throughout both run‐in and supplemented periods, with the exception of vitamin C, this may be a contributing factor increased CVD risk (IOM, 1997b).
As was discussed before, perhaps avocado supplementation led to the notion that its health benefits made it less necessary to make healthy choices in terms of selecting foods rich in fiber and vitamins A and E (e.g. fruit and vegetables) (Roehrs et al., 2011; Gey & Puska, 1989;
Lu et al., 2000).
Carbohydrate was displaced by 719%, perhaps due to the large decreases in fiber and sugar intake observed. Sugar was displaced by 3365%. Since sugar is present in a very small amount, 0.426 g, it is not surprising that this amount is displaced by such large percentage. However, the decrease in sugar intake from other food sources in the diet helps lower CVD risk (Aller et al., 2011). Additionally, D‐mannoheptulose, the primary sugar found in avocados (approximately 4 g/fruit) has a glycemic index of about zero, and has been shown to support blood glucose control and weight management, contributing positive effects in lowering CVD risk as well (Shaw et al., 1980). The displacement in total fiber may be due to satiety effects by avocado supplementation (Wein et al, 2013).
58 Saturated fat displacement was ‐205%, indicating that there was an increased intake of
saturated fat from the rest of the diet during supplementation. This has negative implications in lowering CVD risk as saturated fat is known to have the greatest effect on raising LDL in the lipid profile as compared with other dietary fats (Alissa & Ferns, 2012).
These displacement values indicate that there are increased sources of saturated fat in the supplemented diet such as animal fats.
Total food weight was displaced by approximately 146% while the total calorie intake
was displaced by 80%. This reflects that the avocado supplemented to the participants were incorporated rather than added into their diets during the study period. If they were simply added to the diet, food weight and energy intake would both be closer to 0% displacement. These displacement values tell us that the diets supplemented with avocado most likely consisted of less amounts of food with approximately the same caloric value, indicating that the foods consumed may have been more calorically dense. There is a great likelihood that the large increases in MUFA and PUFA may account for these calorically dense foods. However there is a chance that increased saturated fat food sources could have also contributed.
Satiety induced by avocados is supported by the displacement of dietary fiber (138%).
Because avocados provide several nutrients that promote feelings of fullness such as fats and fiber, this may have discouraged the intake of other sources of fiber that can lead to
59 digestive discomfort (Wein et al., 2013). Although the previous study on the effect of
avocado on satiety indicated a decrease total energy intake, this was not observed in the present study (Wein et al., 2013). However, considering that food weight was reduced in the overall diet, perhaps the consumption of greater amounts of fats were incorporated in the form of oils and nuts that were added to salads, a popular method for integration of avocados into the meal. Oils are calorically dense but don’t contribute to the overall volume of the meal, a determinant for satiety (Ouyang et al., 2006; Rolls, 2009).
The caloric displacement was 80%, indicating that there was a reduction in total energy from the diet excluding avocados. Despite introducing a calorically dense food such as avocados (medium‐energy dense category) into the diet, the total energy intake was only raised minimally, further supporting its effect on satiety.
Although the avocado supplementation diets did not show a significantly decreased level of total energy intake, its ability to displace 80% of its total energy suggests potential in caloric restriction. Caloric restriction studies have shown reduced levels of total cholesterol, LDL, and triglycerides in obese women who were calorie‐restricted by 30%
(Klempel et al., 2012). Perhaps through its effect on satiety, avocado consumption can be incorporated into the diet to aid in the lowering of total energy intake so that the same improvements in lipid profile can be achieved.
60 Compared to NHANES data for avocado consumers, their findings of increased diet
quality and intake of some shortfall nutrients is congruent with some of the displacement results from the present study (Fulgoni et al., 2013). MUFA, PUFA, vitamin K, magnesium, potassium and sodium were all displaced in favor of lowering CVD risk (Table 11).
Although there was insignificance in the displacement results, the values support
existing literature on improved diet quality and cardiovascular health effects (Fulgoni et al.,
2013). Implications of improving CVD risk is similar to that of almond‐supplementation.
Food weight, carbohydrate intake, sugar intake, MUFA, and PUFA were similarly displaced in both supplementation diets in favor of improving cardiovascular health. In Table 11, although there are displacement results that may indicate the potential to raise CVD risk, it should be noted that some components such as dietary fiber and vitamin C are still consumed in adequate amounts whereas those that may be deficient were consistently deficient between run‐in and supplementation periods. Therefore, considering the positive effects of avocado in displacement discussed, in this paper recommendation for lowering
CVD risk should be reasonable. However, because of the lack of significance, future studies should consider utilizing larger sample sizes and perhaps longer study periods, as was done in the almond‐supplementation study (Jaceldo‐Siegl et al., 2004).
61 Table 11
Summary of Nutrient Displacement Values that Lower and Raise CVD Risk.
Components that reduce CVD risk Components that increase CVD risk Food weight = 146% Fat= ‐58% Total energy = 80% Saturated fat = ‐205% Carbohydrate = 719% Protein = ‐278% Sugar = 3365% Fiber = 139% MUFA = ‐54% Soluble fiber = 98% PUFA = ‐77% Vitamin A = 373% Omega 3 = 8.66% Carotene = 555% Omega 6 =‐40.5 Beta‐carotene = 373% Vitamins B1, B2, B3, B6 = ‐425%, ‐439%, Vitamin C = 185% ‐115%, ‐109 Vitamin K = 82% Vitamin E = 160% Magnesium = 23.2% Iron = 377% Potassium = 6.43% Sodium = 5586% Selenium = ‐5785%
Relationship between Nutrient Displacement and Plasma Lipid Changes
As a follow‐up study to the Cal Poly Avocado study that examined the effect of avocado consumption on lipid profile, one of the objectives of the present study was to determine if there is a relationship between the displacement of certain nutrients and changes in lipid profile. Since the relationship between the two variables is such that the change in plasma lipids may be a function of the displacement of a specified nutrient, the regression analysis method was most appropriate.
The results of the primary study indicated that there was an increase in non‐HDL to HDL
ratio in the control but not in the avocado‐enriched treatment group (Johnson, 2012).
62 Additionally, the avocado‐enriched group showed an increase in cholesterol ratio during run‐
in and a decline over the treatment period. Since only 13 of the original participants that underwent the avocado‐enriched treatment were included for the purposes of the present study, results were not directly comparable. None of the relationships examined in the present study yielded significant regression coefficients, this is possibly due to inadequate sample size. Although non‐significant t‐statistics shouldn’t be interpreted since the regression coefficient has a high probability of being zero, we will still discuss some relationships observed as almost all of them correspond to literature. Due to the non‐ significance and small value of the regression coefficients for all the relationships examined, we will only consider whether the relationship is negative or positive.
Relationship between MUFA displacement and TC, LDL, and TC:HDL was positive,
meaning that these plasma lipid components increase as MUFA is removed from the diet, congruent with randomized clinical trial results that substituted carbohydrate intake with
MUFA (Mensink & Katan, 1992; Gardner & Kraemer, 1995). The same positive relationship observed between PUFA displacement and LDL and LDL:HDL is similarly supported. The role of MUFA and PUFA in modification of plasma cholesterols and triglycerides can contribute to lower CVD risk (Fernandez & West, 2005).
The positive relationship between saturated fat displacement and LDL and negative relationship between trans fat intake on total cholesterol:HDL was also found in other
63 studies (Alissa & Ferns, 2012; Mensink & Katan, 1992). This may suggest that the
displacement of saturated fat observed in this study can increase LDL while the changes in trans fat intake can increase total cholesterol.
The positive relationship between fiber displacement and total cholesterol might imply that removing fiber from the diet will increase total cholesterol levels, as supported by controlled trials which found decreased total cholesterol and LDL using the same method of regression analysis (Brown et al., 1999). The 5 oz pulp of avocado supplemented in the present study provides approximately 9‐10 g of total fiber to the diet, which corresponds to the 2‐10 g/d of fiber supplemented in these controlled trials. In our study, there was a negative relationship between fiber displacement and LDL levels, however. A possible reason for this might be that the fiber is consumed as food items that also contains higher levels of LDL‐raising nutrients such as carbohydrate (Wylie‐Rosett, J., Aebersold, K., Conlon,
B., Isasi, C.R., & Ostrovsky, N.W., 2014).
Several randomized controlled clinical trials have found negative relationships between antioxidant supplementation or fruit and vegetable intake on lipid profile (Roehrs et al.,
2011; Gey & Puska, 1989; Lu et al., 2000). All antioxidants measured in the present study showed a positive relationship between its displacement and plasma lipid components, in support of the popular claim that antioxidants can decrease CVD risk. Perhaps these lipid effects can be related to studies that have found that vitamin A, carotenoids, and vitamin E
64 to be inversely associated with cardiovascular events such as ischemic heart disease
mortality or myocardial infarctions (Gey & Puska, 1989; Morris, Kritchevsky, & Davis, 1994).
Vitamin C displacement was positively associated with change in LDL, perhaps contributing to a decrease total cholesterol as supported by a recent randomized crossover trial (Soriano‐
Maldonado, Hidalgo, Arteaga, de Pascual‐Teresa, & Nova, 2014). The regression coefficient of selenium is the smallest out of all variables examined, so it will not be discussed, however it should be noted here that its cardioprotective potential is still controversial, as its ability to increase LDL and total cholesterol might counterbalance its effects as an antioxidant
(Stranges et al., 2011; Laclaustra, stranges, Navas‐Acien, Ordovas, & Guallar, 2010).
As stated previously, relationships as interpreted by regression coefficients from regression analyses conducted between nutrient displacement values and plasma lipid changes were not significant. However, it is interesting to note that most of the relationships examined for this study yielded direction of changes that were congruent with most of the existing literature. It should also be noted that the magnitude of these changes are very minimal, with the greatest coefficient being 0.5352. Considering the lack of statistical significance of the regression analyses, it is concluded that there is no relationship between nutrient displacement and plasma lipid changes in the present study. However, we saw that most of the relationships observed here, however non‐significant or small, were
65 supported by literature. A repeated study in the future might include more participants to
increase the sample size for better statistical power and analysis of these relationships.
Limitations
Several limitations exist in the present study that may have set boundaries for the ability to fully comprehend the extent of overall dietary impact of avocados in cardiovascular health implications. Since the present study was not developed at the time of the primary study when data was collected, the procedure utilized was not designed to obtain the data for our purposes. As a result, accuracy and representability may have been compromised.
The 24‐hour recall data that was used was originally obtained to measure adherence, therefore not many recalls were obtained from the participants. The lack of significance in the data might be attributed to an inadequate sample size as well as inadequate representability of data from each study period. Post hoc statistical power results are provided in Tables 13, 14, and 15. The statistical power of the study in terms of each nutrient variable analyzed as well as the required sample size to detect the observed difference at a significant level were included. The nutrient component analysis for the dietary recalls was also carried out during the primary study. Therefore, its process was not catered to the purposes of the present study either. Although the majority of the nutrient components provided contributed to our evaluation of CVD risk, a few of those that might have yielded meaningful findings were not included.
66 Table 13
Post Hoc Statistical Power and Required Sample Size Calculations for Diet Composition.
Nutrient Power (%) Sample Size Nutrient Power (%) Sample Size Wgt (g) 5 453 Vit E‐a‐Toco (mg) 3 2611 Cals (kcal) 7 228 Folate (mcg) 26 29 FatCals (kcal) 7 228 Vit K (mcg) 10 110 SatCals (kcal) 7 228 Panto (mg) 13 74 Prot (g) 7 228 Calc (mg) 6 294 Carb (g) 11 88 Copp (mg) 13 74 Fib (g) 3 12,700 Iron (mg) 16 55 SolFib (g) 7 228 Magn (mg) 9 133 Sugar (g) 8 172 Mang (mg) 5 704 Fat (g) 7 228 Phos (mg) 11 88 SatFat (g) 8 172 Pot (mg) 20 41 MonoFat (g) 17 48 Sel (mcg) 5 535 PolyFat (g) 10 110 Sod (mg) 22 36 TransFat (g) 8 172 Zinc (mg) 9 133 Chol (mg) 3 12,700 Omega3 (g) 9 133 Water (g) 65 14 Omega6 (g) 8 172 Vit A‐RAE (RAE) 5 453 Alc (g) 3 317,997 Caroten (RE) 7 228 Caff (mg) 9 140 Retinol (RE) 5 453 Chln (mg) 26 29 BetaCaro (mcg) 8 172 Vit B1 (mg) 13 74 Vit B2 (mg) 22 36 Vit B3 (mg) 13 74 Vit B6 (mg) 22 36 Vit B12 (mcg) 10 110 Vit C (mg) 11 88 Vit D‐IU (IU) 20 41 Vit D‐mcg (mcg) 20 41
67 Table 14
Post Hoc Statistical Power and Required Sample Size Calculations for Nutrient Displacement.
Nutrient Power (%) Sample Size Nutrient Power (%) Sample Size Wgt (g) 17 48 Folate (mcg) 5 453 Cals (kcal) 6 294 Vit K (mcg) 17 48 FatCals (kcal) 5 704 Panto (mg) 5 453 SatCals (kcal) 3 12700 Calc (mg) 5 453 Prot (g) 3 12700 Copp (mg) 3 317997 Carb (g) 22 36 Iron (mg) 22 36 Fib (g) 28 27 Magn (mg) 4 1225 SolFib (g) 96 4 Mang (mg) 3 317997 Sugar (g) 8 172 Phos (mg) 4 1225 Fat (g) 5 704 Pot (mg) 6 294 SatFat (g) 3 12700 Sel (mcg) 14 65 MonoFat (g) 3 12700 Sod (mg) 22 36 PolyFat (g) 5 453 Zinc (mg) 5 704 Water (g) 14 65 Omega3 (g) 13 74 Vit A‐RAE (RAE) 5 704 Omega6 (g) 14 65 Caroten (RE) 3 12700 Chln (mg) 3 2611 BetaCaro (mcg) 4 1225 Vit B1 (mg) 6 294 Vit B2 (mg) 10 105 Vit B3 (mg) 11 88 Vit B6 (mg) 4 1225 Vit C (mg) 16 55 Vit E‐a‐Toco (mg) 54 12
68 Table 15
Post Hoc Statistical Power and Required Sample Size Calculations for Associations.
Power (%) Sample Size
TC 8 172 MUFA % displacement vs TC:HDL 9 140 LDL 28 27 TC 5 640
Fiber % displacement vs LDL 6 314 TC:HDL 11 88 LDL 8 163 PUFA % displacement vs LDL:HDL 38 18 LDL 7 243 Vitamin A % displacement vs LDL:HDL 4 1225 LDL 3 6472 Carotene % displacement vs LDL:HDL 6 294 LDL 2 N/A Beta‐carotene % displacement vs LDL:HDL 7 228 LDL 7 192 Vitamin C % displacement vs LDL:HDL 18 45 LDL 50 13 Vitamin E % displacement vs LDL:HDL 40 17 LDL 14 62 Iron % displacement vs LDL:HDL 11 88 LDL 8 155 Selenium % displacement vs LDL:HDL 22 35 HDL 4 864 Carbohydrate % displacement vs TC:HDL 3 2611 HDL 3 3908 Trans fat intake vs TC:HDL 26 29 Dietary cholesterol intake vs HDL 14 65 TC 3 19,854 Total calories % displacement vs LDL 4 1083 TC 5 640 Carbohydrate % displacement vs LDL 6 275 Saturated fat % displacement vs TC 5 492 69
For future research in this field, a few more things can be considered to achieve results that can allow us to more successfully understand the dietary implications of avocado supplementation in terms of CVD risk. First, increasing the number of participants as well as the number of randomly selected days on which 24 hour recalls will be collected might result in better statistical power and representability of the sample population. Also, as we were previously speculating the effects of satiety induced by avocados to affect dietary measures such as total energy intake, food weight, and fiber intake, providing a measure for satiety such as the Visual Analog Scale (VAS) would allow us to accurately determine if changes in these components can be attributed to its effects. Finally, expanding the nutrient component analyses to include other nutrients known to have significant effects on cardiovascular health, will help gain a more extensive understanding of the dietary implications from avocados. An example of one such nutrient would be lycopene, studied for its role as an antioxidant and anti‐inflammatory agent in CVD risk reduction (Bohm,
2012). Also, including different aspects of diet analysis such as source of protein can also provide insight into CVD risk raising and lowering effects (e.g. animal protein have higher
CVD risk implications than plant proteins) (Jaceldo‐Siegl et al., 2004).
70
CHAPTER 6
CONCLUSION
Implications of the Study
Realizing the full potential of a recommended food item requires that we understand its ability to not only affect the biology of the human body, but also its effect on the individual’s lifestyle, such as dietary pattern. It remains to be a component in nutrition research that should be developed.
There are economic as well as professional implications associated with the results from the present study. As was discussed previously, avocado remains to be a popular food item that is high in demand and supplied in increasing amounts in the US market. For this reason, it becomes all the more important to understand its health implications so that the public can be better informed and economic opportunities can be developed. The results of this study helped us move one step closer towards understanding the full potential of avocado consumption in improving cardiovascular health. Knowing that it can improve dietary pattern by encouraging increased intake of other cardioprotective food items will help dietetics professionals provide dietary recommendations and achieve health results much more successfully.
Although the results obtained from this study was almost consistently insignificant with
the exception of soluble fiber displacement, values for each aspect of the analyses was still
71
able to provide valuable insight into the potential for avocados to benefit cardiovascular health. Our study set out to fulfill its purpose of gaining a better understanding of the ability of avocado consumption to affect dietary pattern as measured by diet compositional changes, nutrient displacement values, and relationships between these displacement values and plasma lipid changes. Results have indicated a pattern in compositional and displacement values of MUFA, PUFA, soluble fiber, and total energy intake that supports previous findings of improved diet quality (Fulgoni et al., 2013). Although it can’t be concluded that avocados should be recommended as a supplement to obtain the cardiovascular benefits as observed in this study, these results should be regarded as a basis for future research studies in which they can be reexamined and reevaluated.
72
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85
APPENDIX A
IRB APPROVAL LETTER
86 87
APPENDIX B 24‐
HOUR RECALL WORKSHEET
88
24‐Hour Recall Worksheet
Instructions: Please fill out the following worksheet to the best of your ability. It is important that you include both foods and beverages. Please be sure to list the approximate quantity (count, volume, weight) of each listed food or beverage, and how it was prepared (cooking method) if applicable.
Participant Number:
Date of Recall:
Meal Foods and Beverages Breakfast
Snack
Lunch
89
Snack
Dinner
Snack
90
APPENDIX C
PARTICIPANT CHARACTERISTICS FROM CAL POLY AVOCADO STUDY
91
Table 12 Two‐tailed t‐test results for group differences in baseline participant characteristics
(Johnson, 2012).
Characteristic p‐value Age 0.640 Gender 1.000 Height (cm) 0.368 Weight (kg) 0.356 BMI (kg/m2) 0.397 Percent fat (%) 0.356 Total cholesterol (mg/dL) 0.457 HDL cholesterol (mg/dL) 0.521 LDL cholesterol (mg/dL) 0.457 Cholesterol ratio 0.979 Triglycerides (mg/dL) 0.837
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APPENDIX D
RESEARCH CERTIFICATE
93
94
APPENDIX E
JOURNAL ARTICLE
95
The effect of avocado consumption on food displacement in terms of cardiovascular disease risk
Yee‐Chi (Christina) Chen, Dr. Bonny Burns‐Whitmore, Dr. David Edens, Dr. Harmit Singh, and Dr. Thomas Spalding
California State Polytechnic University, Pomona
Abstract
Many functional foods have been studied for their ability to lower cardiovascular disease (CVD) risk. Avocados contain significant amounts of cardioprotective components such as monounsaturated fats, polyunsaturated fats, antioxidants, fiber, and potassium, among other nutrients (1). Most studies have been done on the direct health effects of avocado consumption, whereas few have looked at its ability to affect overall diet pattern (2,3). In the present study, the ability of the avocado to affect diet in terms of lowering CVD risk was studied through evaluating nutrient profile, nutrient displacement, and correlation between changes in nutrient intake and changes in plasma cholesterol of 13 free‐living college students. Participants underwent a 4‐week avocado‐free diet period before the 8‐ week treatment period of 5 oz of avocado/day. Twenty‐four‐hour dietary recalls were collected and blood samples were drawn for lipid profile analyses. Nutrients of interest selected for analyses were based on their ability to affect CVD risk, including but not limited to antioxidant and dietary fat components. Although the results obtained was almost consistently insignificant with the exception of soluble fiber displacement, results still indicated a pattern in compositional and displacement values of MUFA, PUFA, soluble fiber, and total energy intake that supports previous findings of improved diet quality with avocado consumption (2). It can’t be concluded that avocados should be recommended as a supplement to obtain the cardiovascular benefits. However, these results should be regarded as a basis for future research where they can be reexamined and reevaluated.
Introduction
Cardiovascular disease (CVD) has been found to be the leading cause of morbidity and mortality in Americans (4). The American Heart Association, National Cholesterol Education Program, Dietary Guidelines for Americans, and Total Lifestyle Change program are some examples of the effort put forth by government as well as voluntary organizations to reduce the risk of CVD in the US population (4,5,6,7). What is consistent among these guidelines is the restriction of saturated fat, trans fat, and cholesterol intake along with consumption of fish and other sources of polyunsaturated or monounsaturated fats. Diets rich in fruit and vegetables are promoted as they are excellent sources of fiber and antioxidants. Other restrictions include added sugars and sodium. These guidelines are based on research findings that have found these nutrient components to be contributing factors to the development of CVD. Cardioprotective properties of tree nuts have been compared to the avocado fruit due to their similar nutritional components (1). Although the
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research on many similar functional foods are extensive, most focus on the direct health implications determined by measures such as lipid profiles (8).
Since nutritional guidelines target the overall diet, there should be a measure of how a recommended functional food, such as the avocado, can affect the overall diet pattern besides its direct biological effects. One such measure is food displacement, defined by Jaceldo‐Siegl as “an inverse measure of the degree to which the supplement induced a change in the content of a particular nutrient in the supplemented diet” (8). It has been supported by several research studies that the consumption of avocado has led to improved lipid profiles, anthropometric measures, overall diet quality, and satiety (2,3,8,9,10,11,12). Their findings suggest that the avocado fruit can be incorporated into the diet for its benefits in lowering CVD risk.
The general purpose of this study is to address the lack of knowledge in the field of overall dietary impact as a result of avocado consumption. Specifically, we will be examining dietary impact via 1) calculating diet composition changes of selected nutrients, 2) calculating nutrient displacement percentages of selected nutrients, and 3) examining the association between nutrient displacement and changes in the lipid profile components.
Materials and Methods
This study was done as a follow‐up to another study on “The effect of regular avocado feedings on the serum lipids and body composition of healthy, free‐living students” conducted at the California State Polytechnic University, Pomona in 2012 (Cal Poly Avocado study) (13). Results from the present study was meant to build on previous findings. Therefore, we will outline the methodology that was used in the primary study.
Participants
Participants selected for the primary study were all students attending California State Polytechnic University, Pomona. The study was conducted to examine the effects of avocado consumption on serum lipid profile and body composition of free‐living and healthy individuals. The study was approved by the California State Polytechnic University, Pomona Institutional Review Board under Protocol 11‐136. Participants involved met the following criteria: between the ages of 18 and 40, free from chronic disease with the exception of high blood cholesterol, had stable diet and exercise pattern, were open to eating avocados daily, were not on antibiotic, steroid, or cholesterol‐lowering medication, were not pregnant and had not been for the previous 12 months, and were not on hormonal medications with the exception of birth control.
Experimental Design
The study was a parallel design with two dietary interventions: 1) avocado‐free control and 2) avocado‐enriched. Participants were randomly assigned to each of the two interventions, making sure that equal numbers of each gender were in each group. All 26
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participants began with a four‐week avocado‐free run‐in period followed by an eight‐week dietary intervention period in which they were randomly assigned to either the control or avocado‐enriched group. For the purposes of the present study, only the data from those participants assigned to the avocado‐enriched treatment group were included. Since all participants were put on a 4‐week avocado‐free run in period, the included participants served as their own control.
Dietary treatment
Avocados that were used in this study were provided by Index and Fresh and picked up at the distribution facility in Colton, CA by study personnel. All avocados were Hass variety, grown in Chile, size #70, and obtained in an unripe condition. Each avocado contained approximately 5 oz of pulp. Ripened avocados, assessed by finger pressing, were stored in a refrigerator at 2 degrees Celsius for participant pick‐up on a weekly basis. In this way, all participants consumed avocados that were similar in ripeness to maintain consistency.
The avocado‐free diet, utilized by all participants in the four‐week run‐in and those assigned to the control diet during the eight‐week treatment period, required participants to maintain normal dietary and exercise patterns while avoiding ingestion of any avocado or avocado‐derived products. The avocado‐enriched diet was utilized by the avocado‐enriched treatment group during the eight‐week treatment period. Normal diet and exercise patterns were required of the participants while consuming 5 oz of avocado a day. They were instructed to avoid ingesting other sources of avocado, and were encouraged to incorporate it rather than add it into their diet. Changes in dietary and exercise patterns, as well as dietary adherence, were assessed with 24‐hour recalls and an unusual diet diary.
Data collection
We only used data collected from the blood sampling and 24‐hour diet recall from the original Cal Poly Avocado study. Blood samples were collected at weeks 0, 4, and 12. One recall was completed by participants on a randomly chosen day from the run‐in period, and three more from the treatment period.
A nutrient component analysis was conducted with ESHA computer software by the primary study personnel using data collected from the 24‐hour diet recalls. The analyses provided nutrient composition values in the diets of the 26 participants.
Data analysis
The nutrients of interest for this study were selected based on evidence for their role in affecting CVD risk. Nutrient profile were analyzed for changes in diet composition where percentage differences will be calculated for each nutrient. To calculate the nutrient displacement values, we used the same equation that was used in Jaceldo‐Siegl’s study where they studied food displacement in almond supplementation (8). The equation is as
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follows: [(S + R – A)/S] x 100, where R=nutrient value from run‐in period, A=nutrient value from avocado‐supplemented period, and S=nutrient value in the supplemented 5 oz Hass avocado. In order to analyze associations between nutrient changes and lipid profile, regression analysis was conducted to test if plasma lipid changes was a function of specific nutrient displacement.
Statistical methods
13 participants were included for the present study. Respective standard deviation (SD) and standard error of the mean (SEM) values were calculated. Due to the nature of the study, the paired sample Wilcoxon signed ranking test was used to determine the significance (p‐value) of the differences between nutrient values from the run‐in and avocado‐supplemented period. For displacement values, the same statistical method was used to test the null hypothesis that displacement equals zero. Since multiple hypotheses were tested on the same data set, the Bonferroni adjustment method was utilized where the new critical level for determining significance was 0.001 for both diet composition and nutrient displacement data. For examining relationships between lipid profile components and nutrient displacement, individual values were used for regression analysis. The p‐value determined for the regression analysis tests the null hypothesis that the regression coefficient is equal to zero, i.e. plasma lipid does not change as nutrient displacement changes. The statistical analyses were performed using Prism GraphPad 6.0 software for Windows statistical software package (14).
Results
Primary study results included an analysis of participant characteristics as well as baseline plasma lipids and found that there were no significant group differences among them (13). Percent adherence was also calculated by using the unusual diet diaries for the primary study. This was calculated to be 99.0% + 0.02% for the run‐in diet, 98.4% + 0.03% for the treatment phase, 99.5% + 0.01% for the avocado‐free control group, and 97.3% + 0.05% for the avocado‐enriched group.
In analyzing the diet composition for total calories consumed, monounsaturated and polyunsaturated fat, fiber, antioxidant vitamin and minerals, carbohydrates, cholesterol, saturated fat, and trans fat, there were no significant differences observed for the nutrient profile as calculated by the Wilcoxon signed ranking test (Table 1). For nutrient displacement of monounsaturated and polyunsaturated fat, fiber, antioxidant vitamin and minerals, carbohydrate, and trans fat, again, no significant differences were observed (Table 2). Soluble fiber was the only component that showed significance in displacement of approximately 97% in the supplemented diet. Regression analysis between either nutrient displacement or changes in intake and plasma lipid changes, also yielded no significant results. For the associations observed, the trends were presented as either positive or negative due to the small regression coefficients that were calculated (Table 3).
99 Table 7 Mean diet compositional changes of participants between run‐in and supplemented period.
Avocado‐ Run‐in period (H) (A‐H) % ((A‐H)/H x 100) supplemented period mean SD mean SD mean SEM % p‐value* Wgt (g) 2197.11 709.63 2131.30 762.17 ‐65.81 172.16 ‐3.00 0.74 Cals (kcal) 2539.28 962.13 2586.26 1525.18 46.98 491.48 1.85 0.64 FatCals (kcal) 838.57 404.08 1150.17 1138.13 311.60 340.00 37.16 0.64 SatCals (kcal) 245.19 131.61 328.23 339.18 83.04 91.92 33.87 0.59 Prot (g) 90.19 49.63 100.73 89.53 10.54 27.10 11.68 >0.999 Carb (g) 344.25 167.76 268.27 85.43 ‐75.97 55.44 ‐22.07 0.45 Fib (g) 31.24 30.07 27.49 7.70 ‐3.76 8.62 ‐12.03 0.95 SolFib (g) 0.93 1.13 0.99 0.78 0.06 0.37 6.48 0.64 Sugar (g) 107.04 63.22 93.13 43.48 ‐13.91 18.43 ‐13.00 0.59 Fat (g) 93.33 45.03 127.98 126.53 34.65 37.84 37.13 0.64 SatFat (g) 27.24 14.62 36.47 37.69 9.23 10.21 33.87 0.59 MonoFat (g) 14.23 15.16 35.61 45.42 21.38 14.75 150.28 0.31 PolyFat (g) 5.73 5.76 10.30 13.00 4.57 4.36 79.84 0.50 TransFat (g) 1.44 2.53 1.15 0.95 ‐0.29 0.81 ‐19.87 0.59 Chol (mg) 245.23 161.76 335.23 429.70 90.00 118.20 36.70 0.95 Water (g) 1273.95 611.85 1209.85 712.46 ‐64.10 212.73 ‐5.03 0.38 Vit A‐RAE (RAE) 379.10 643.16 351.98 284.79 ‐27.12 181.78 ‐7.15 0.74 Caroten (RE) 616.69 1264.74 521.01 630.90 ‐95.68 349.79 ‐15.51 0.64 Retinol (RE) 70.76 90.21 91.47 93.74 20.71 41.80 29.27 0.74 BetaCaro (mcg) 3012.20 6247.96 2768.31 3484.22 ‐243.89 1799.81 ‐8.10 0.59 Vit B1 (mg) 0.92 0.99 1.52 1.79 0.60 0.63 64.56 0.41 Vit B2 (mg) 0.95 1.00 2.03 2.33 1.07 0.80 112.48 0.24 Vit B3 (mg) 14.26 18.54 20.09 26.25 5.83 9.68 40.87 0.41 Vit B6 (mg) 1.24 1.46 2.10 2.48 0.86 0.87 69.56 0.24 Vit B12 (mcg) 3.25 5.71 3.70 3.54 0.45 1.92 13.96 0.50 Vit C (mg) 128.09 113.11 117.41 119.75 ‐10.68 51.27 ‐8.34 0.45 Vit D‐IU (IU) 40.75 74.28 152.64 369.01 111.89 107.25 274.56 0.27 Vit D‐mcg (mcg) 1.01 1.85 3.79 9.22 2.78 2.68 276.36 0.27 Vit E‐a‐Toco (mg) 6.59 8.36 4.91 3.04 ‐1.68 2.31 ‐25.56 0.89 Folate (mcg) 244.32 277.74 288.62 73.66 44.30 79.81 18.13 0.19 Vit K (mcg) 55.04 126.06 60.51 77.04 5.48 38.21 9.95 0.50 Panto (mg) 2.95 3.74 4.47 3.73 1.52 1.69 51.72 0.41 Calc (mg) 641.03 382.00 682.59 408.44 41.56 93.26 6.48 0.68 Copp (mg) 0.76 0.63 1.00 0.52 0.23 0.25 30.55 0.41 Iron (mg) 16.72 10.45 14.32 7.49 ‐2.40 3.41 ‐14.35 0.34 Magn (mg) 151.47 157.22 183.10 88.65 31.62 46.55 20.88 0.54 Mang (mg) 2.25 2.83 2.00 0.77 ‐0.26 0.71 ‐11.43 0.79 Phos (mg) 553.93 618.71 734.88 673.68 180.95 270.98 32.67 0.45 Pot (mg) 1380.85 1296.92 2054.48 1372.24 673.63 589.21 48.78 0.27 Sel (mcg) 43.74 72.42 77.16 127.83 33.43 42.98 76.43 0.38 Sod (mg) 3652.21 1293.25 3029.01 1371.74 ‐623.21 450.05 ‐17.06 0.24 Zinc (mg) 9.17 14.04 10.87 15.05 1.70 6.25 18.51 0.54 Omega3 (g) 0.36 0.35 0.56 0.59 0.20 0.22 55.25 0.54 Omega6 (g) 4.00 4.39 8.16 12.28 4.15 3.88 103.68 0.59 Alc (g) 2.45 5.92 1.72 4.15 ‐0.73 2.17 ‐29.94 >0.999 Caff (mg) 25.29 71.14 21.17 38.39 ‐4.13 22.39 ‐16.31 0.55 Chln (mg) 88.84 159.12 158.33 310.76 69.49 102.11 78.21 0.19
Note: *Wilcoxon signed ranking test used because of small sample and lack of normality in distribution; The values are tested against the H0 of 0% displacement. **To control for number of variables measured, significance is determined at 0.05/47 = 0.001.
100 Table 8 Mean nutrient displacement values.
Avocado Nutrient Habitual Avocado diet Absolute (D) % displacement supplement H A S S+H‐A D/S * 100 SEM p value* Wgt (g) 2197.11 2131.30 142.00 207.81 146.34 121.24 0.31 Cals (kcal) 2539.28 2586.26 237.14 190.16 80.19 207.25 0.68 FatCals (kcal) 838.57 1150.17 196.81 ‐114.79 ‐58.32 172.75 0.79 SatCals (kcal) 245.19 328.23 27.22 ‐55.82 ‐205.06 337.67 0.95 Prot (g) 90.19 100.73 2.78 ‐7.75 ‐278.59 973.53 0.95 Carb (g) 344.25 268.27 12.27 88.24 719.22 451.90 0.24 Fib (g) 31.24 27.49 9.66 13.41 138.91 89.23 0.17 SolFib (g) 0.93 0.99 2.90 2.84 97.92 12.70 0.0002 Sugar (g) 107.04 93.13 0.43 14.34 3365.86 4326.87 0.59 Fat (g) 93.33 127.98 21.87 ‐12.78 ‐58.45 173.04 0.79 SatFat (g) 27.24 36.47 3.02 ‐6.20 ‐205.05 337.68 0.95 MonoFat (g) 14.23 35.61 13.92 ‐7.47 ‐53.65 106.00 0.95 PolyFat (g) 5.73 10.30 2.58 ‐1.99 ‐76.95 168.70 0.74 Water (g) 1273.95 1209.85 102.67 166.76 162.43 207.21 0.38 Vit A‐RAE (RAE) 379.10 351.98 9.94 37.06 372.88 1828.82 0.79 Caroten (RE) 616.69 521.01 21.02 116.69 555.26 1664.38 0.95 BetaCaro (mcg) 3012.20 2768.31 89.46 333.35 372.62 2011.86 0.84 Vit B1 (mg) 0.92 1.52 0.11 ‐0.48 ‐424.56 553.73 0.68 Vit B2 (mg) 0.95 2.03 0.20 ‐0.87 ‐439.26 402.53 0.49 Vit B3 (mg) 14.26 20.09 2.71 ‐3.12 ‐114.95 356.81 0.45 Vit B6 (mg) 1.24 2.10 0.41 ‐0.45 ‐109.46 211.12 0.84 Vit C (mg) 128.09 117.41 12.50 23.18 185.47 410.32 0.34 Vit E‐a‐Toco (mg) 6.59 4.91 2.80 4.48 160.22 82.49 0.04 Folate (mcg) 244.32 288.62 126.38 82.08 64.95 63.15 0.74 Vit K (mcg) 55.04 60.51 29.82 24.34 81.63 128.12 0.31 Panto (mg) 2.95 4.47 2.07 0.55 26.52 81.55 0.74 Calc (mg) 641.03 682.59 18.46 ‐23.10 ‐125.15 505.18 0.74 Copp (mg) 0.76 1.00 0.24 0.01 3.24 104.60 > 0.9999 Iron (mg) 16.72 14.32 0.87 3.26 376.89 393.42 0.24 Magn (mg) 151.47 183.10 41.18 9.56 23.21 113.04 0.84 Mang (mg) 2.25 2.00 0.21 0.47 220.98 333.71 > 0.9999 Phos (mg) 553.93 734.88 76.68 ‐104.27 ‐135.98 353.39 0.84 Pot (mg) 1380.85 2054.48 719.94 46.31 6.43 81.84 0.68 Sel (mcg) 43.74 77.16 0.57 ‐32.86 ‐5785.11 7567.64 0.38 Sod (mg) 3652.21 3029.01 11.36 634.57 5585.97 3961.68 0.24 Zinc (mg) 9.17 10.87 0.97 ‐0.73 ‐75.75 647.26 0.79 Omega3 (g) 0.36 0.56 0.22 0.02 8.66 99.83 0.41 Omega6 (g) 4.00 8.16 2.95 ‐1.20 ‐40.55 131.24 0.38 Chln (mg) 88.84 158.33 36.35 ‐33.13 ‐91.15 280.89 0.89
Note: * Wilcoxon signed ranking test used because of small sample and lack of normality in distribution; The values are tested against the H0 of 0% displacement.**To control for number of variables measured, significance is determined at 0.05/39 = 0.001.
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Table 9 Relationship between a nutrient displacement percentage or nutrient intake and change in plasma lipid component.
Nutrient % displacement or Change in Association* nutrient intake plasma lipid
TC + Hypothesis 6 MUFA % displacement vs TC:HDL + LDL +
TC + Hypothesis 7 Fiber % displacement vs LDL - TC:HDL + LDL + Hypothesis 8 PUFA % displacement vs LDL:HDL + LDL + Vitamin A % displacement vs LDL:HDL +
LDL + Carotene % displacement vs LDL:HDL +
LDL + Beta‐carotene % displacement vs LDL:HDL +
LDL + Hypothesis 9 Vitamin C % displacement vs LDL:HDL - LDL + Vitamin E % displacement vs LDL:HDL + LDL + Iron % displacement vs LDL:HDL + LDL + Selenium % displacement vs LDL:HDL + HDL + Hypothesis 10 Carbohydrate % displacement vs TC:HDL - HDL + Hypothesis 11 Trans fat intake vs TC:HDL - Hypothesis 12 Dietary cholesterol intake vs HDL - TC + Total calories % displacement vs LDL -
TC - Hypothesis 13 Carbohydrate % displacement vs LDL - TC + Saturated fat % displacement vs LDL - Note: *Regression analysis was used, the slope is calculated to measure the degree to which y is a function of x (e.g. plasma lipid changes is a function of nutrient displacement).
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Discussion
The aim of the present study was to examine the effect of avocado consumption on the overall diet through looking at changes in diet composition, nutrient displacement, and the relationship between nutrient displacement and changes in plasma lipids. Insignificant values were obtained for almost all nutrient components with the exception of soluble fiber in nutrient displacement. Despite the insignificance of the results, values for some diet composition, nutrient displacement and some associations between nutrient displacement and lipid profile changes were found to be congruent with existing literature.
Based on what is known about the cardiovascular benefits of caloric restriction and the effects of avocado on satiety, avocado supplementation was expected to affect total energy intake and food weight (3,15). However, non‐significant results were obtained for nutrient intake and nutrient displacement values, preventing us from drawing a sound conclusion that can have overall dietary implications from the effects on satiety caused by avocado.
Studies on the ability of avocado consumption to improve diet quality in terms of the Healthy Eating Index (HEI) as well as increased number of servings of fruit, vegetables, and other cardioprotective dietary habits was observed in the NHANES study (2). The only significance observed from the present study was the displacement of soluble fiber in the supplemented diet by approximately 97%. Since soluble fiber has been associated with cardioprotective function, its large displacement percentage does not support the improved diet quality as observed by NHANES data.
Although nutrients such as monounsaturated fats, polyunsaturated fats, fiber, and other nutrient components studied have been shown in clinical trials to improve plasma lipid profile, this was not reflected in the present study where nutrient displacement and intake changes were examined for its relationship with plasma lipid changes. No significance in regression coefficients were observed, therefore no relationships can be drawn.
Several limitations exist in the present study that may have set boundaries for the ability to fully comprehend the extent of overall dietary impact of avocados in cardiovascular health implications. Since the present study was not developed at the time when data was collected for the primary study, the procedure utilized was not designed to obtain the data for our purposes. As a result, accuracy and representability may have been compromised. The 24‐hour recall data that was used was originally obtained to measure adherence, therefore not many recalls were obtained from the participants. The lack of significance in the data might be attributed to an inadequate sample size as well as inadequate representability of data from each study period. The nutrient component analysis for the dietary recalls was also carried out during the primary study. Therefore, its process was not catered to the purposes of the present study either. Although the majority of the nutrient components provided contributed to our evaluation of CVD risk, a few of those that might have yielded meaningful findings were not included. 103
For future research in this field, a few more things can be considered to achieve results that can allow us to more successfully understand the dietary implications of avocado supplementation in terms of CVD risk. First, increasing the number of participants as well as the number of randomly selected days on which 24 hour recalls will be collected might result in better statistical power and representability of the sample population. Also, as we were previously speculating the effects of satiety induced by avocados to affect dietary measures such as total energy intake, food weight, and fiber intake, providing a measure for satiety such as the Visual Analog Scale (VAS) would allow us to more accurately determine if changes in these components can be attributed to its effects. Finally, expanding the nutrient component analyses to include other nutrients known to have significant effects on cardiovascular health, will help us gain a more extensive understanding of the dietary implications from avocados. An example of one such nutrient would be lycopene, studied for its role as an antioxidant and anti‐inflammatory agent in CVD risk reduction (16). Also, including different aspects of diet analysis such as source of protein can also provide insight into CVD risk raising and lowering effects (e.g. animal protein have higher CVD risk implications than plant proteins) (8).
Realizing the full potential of a recommended food item requires that we understand its ability to not only affect the biology of the human body, but also its effect on the individual’s lifestyle, a component of which is dietary pattern. It remains to be an aspect in nutrition research that should be developed.
There are economic as well as professional implications associated with the results from the present study. As was discussed previously, avocado remains to be a popular food item that is high in demand and supplied in increasing amounts in the US market. For this reason, it becomes all the more important to understand its health implications so that the public can be better informed and economic opportunities can be developed. The results of this study helped us move one step closer towards understanding the full potential of avocado consumption in improving cardiovascular health. Knowing that it can improve dietary pattern by encouraging increased intake of other cardioprotective food items will help dietetics professionals provide dietary recommendations and achieve health results much more successfully.
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Conclusion
Although the results obtained from this study was almost consistently insignificant with the exception of soluble fiber displacement, values for each aspect of the analyses was still able to provide valuable insight into the potential for avocados to benefit cardiovascular health. Our study set out to fulfill its purpose of gaining a better understanding of the ability of avocado consumption to affect dietary pattern as measured by diet compositional changes, nutrient displacement values, and relationships between these displacement values and plasma lipid changes. Results have indicated an interesting pattern in compositional and displacement values of MUFA, PUFA, soluble fiber, and total energy intake that supports previous findings of improved diet quality (2). Although it can’t be concluded that avocados should be recommended as a supplement to obtain the cardiovascular benefits as observed in this study, these results should be regarded as a basis for future research where they can be reexamined and reevaluated.
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1. Dreher, M.L. & Davenport, A.J. (2013). Hass avocado composition and potential health effects. Critical Reviews in Food Science and Nutrition, 53, 738‐750. 2. Fulgoni, V.L. III, Dreher, M., & Davenport, A.J. (2013). Avocado consumption is associated with better diet quality and nutrient intake, and lower metabolic syndrome risk in US adults: results from the National Health and Nutrition Examination Survey (NHANES) 2001‐2008. Nutrition Journal, 12, 1. 3. Wein, M., Haddad, E., Oda, K., & Sabate, J. (2013). A randomized 3x3 crossover study to evaluate the effect of Hass avocado intake on post‐ingestive satiety, glucose and insulin levels, and subsequent energy intake in overweight adults. Nutrition Journal, 12, 155. 4. Lichtenstein, A.H., Appel, L.J., Brands, M., Camethon, M., Daniels, S., Franch H.A., … Wylie‐ Rosett, J. (2006). Diet and lifestyle recommendations revision 2006: a scientific statement from the American Heart Association Nutrition Committee. Circulation, 114, 82‐96. 5. National Heart, Lung, and Blood Institute. (2001). National cholesterol education program: ATP III guidelines at‐a‐glance quick desk reference (NIH Publication No. 01‐3305). Washington, DC: US Government Printing Office. 6. U.S. Department of Agriculture and U.S. Department of Health and Human Services. (2010). Dietary guidelines for Americans, 2010. Washington, DC: US Government Printing Office. 7. National Heart, Lung, and Blood Institute. (2005). Your guide to lowering your cholesterol with TLC (NIH Publication No. 06‐5235). Washington, DC: US Government Printing Office. 8. Jaceldo‐Siegl, K., Sabat`e, J., Rajaram, S., and Fraser, G.E. (2004). Long‐term almond supplementation without advice on food replacement induces favorable nutrient modifications to the habitual diets of free‐living individuals. British Journal of Nutrition, 92, 533‐540. 9. Grant, W.C. (1960). Influence of avocados on serum cholesterol. Proceedings of the Society for Experimental Biology and Medicine, 104, 45‐47. 10. Colquhoun, D., Moores, D., Somerset, S.M., & Humphries, J.A. (1992). Comparison of the effects on lipoproteins and aplipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high‐carbohydrate diet. American Journal of Clinical Nutrition, 56, 671‐677. 11. Carranza J., Alvizouri, M., Alvarado, M.R., Chaves, F., Gomez, M., & Herera, J.E. (1995). Effects of avocado on the level of blood lipids in patients with phenotype II and IV dyslipidemias. Archivos de cardiología de México, 65, 342‐348. 1 Lopez‐Ledesma, R., Frati Munari, A.C., & Hernandez Dominguez, B.C. (1996).
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106 16. Bohm, V. (2012). Lycopene and heart health. Molecular Nutrition & Food Research, 56, 296‐ 303. 17. Dreher, M.L. & Davenport, A.J. (2013). Hass avocado composition and potential health effects. Critical Reviews in Food Science and Nutrition, 53, 738‐750. 18. Fulgoni, V.L. III, Dreher, M., & Davenport, A.J. (2013). Avocado consumption is associated with better diet quality and nutrient intake, and lower metabolic syndrome risk in US adults: results from the National Health and Nutrition Examination Survey (NHANES) 2001‐2008. Nutrition Journal, 12, 1. 19. Wein, M., Haddad, E., Oda, K., & Sabate, J. (2013). A randomized 3x3 crossover study to evaluate the effect of Hass avocado intake on post‐ingestive satiety, glucose and insulin levels, and subsequent energy intake in overweight adults. Nutrition Journal, 12, 155. 20. Lichtenstein, A.H., Appel, L.J., Brands, M., Camethon, M., Daniels, S., Franch H.A., … Wylie‐ Rosett, J. (2006). Diet and lifestyle recommendations revision 2006: a scientific statement from the American Heart Association Nutrition Committee. Circulation, 114, 82‐96. 21. National Heart, Lung, and Blood Institute. (2001). National cholesterol education program: ATP III guidelines at‐a‐glance quick desk reference (NIH Publication No. 01‐3305). Washington, DC: US Government Printing Office. 22. U.S. Department of Agriculture and U.S. Department of Health and Human Services. (2010). Dietary guidelines for Americans, 2010. Washington, DC: US Government Printing Office. 23. National Heart, Lung, and Blood Institute. (2005). Your guide to lowering your cholesterol with TLC (NIH Publication No. 06‐5235). Washington, DC: US Government Printing Office. 24. Jaceldo‐Siegl, K., Sabat`e, J., Rajaram, S., and Fraser, G.E. (2004). Long‐term almond supplementation without advice on food replacement induces favorable nutrient modifications to the habitual diets of free‐living individuals. British Journal of Nutrition, 92, 533‐540. 25. Grant, W.C. (1960). Influence of avocados on serum cholesterol. Proceedings of the Society for Experimental Biology and Medicine, 104, 45‐47. 26. Colquhoun, D., Moores, D., Somerset, S.M., & Humphries, J.A. (1992). Comparison of the effects on lipoproteins and aplipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high‐carbohydrate diet. American Journal of Clinical Nutrition, 56, 671‐677. 27. Carranza J., Alvizouri, M., Alvarado, M.R., Chaves, F., Gomez, M., & Herera, J.E. (1995). Effects of avocado on the level of blood lipids in patients with phenotype II and IV dyslipidemias. Archivos de cardiología de México, 65, 342‐348. 2 Lopez‐Ledesma, R., Frati Munari, A.C., & Hernandez Dominguez, B.C. (1996). Monounsaturated fatty acid (avocado) rich diet for mild hypercholesterolemia. Archives of Medical Research, 27, 519‐523. 29. Johnson, M. (2012). The effect of regular avocado feedings on the serum lipids and body composition of healthy, free‐living students (Unpublished Master’s thesis). California State Polytechnic University, Pomona, California. 30. Motulsky, H. (2014). Prism, GraphPad Software (Version 6.0) (Software). Available from http://www.graphpad.com/scientific‐software/prism/ 31. Klempel, M.C., Kroeger, C.M., Bhutani, S., Trepanowski, J.F., & Varady, K.A. (2012). Intermittent fasting combined with calorie restriction is effective for weight loss and cardio‐ protection in obese women. Nurition Journal, 11, 98.
107 32. Bohm, V. (2012). Lycopene and heart health. Molecular Nutrition & Food Research, 56, 296‐ 303.
108