Health Consequences of Vegetarian Diets
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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION CHAPTER 2 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT HealthFOR SALE Consequences OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION of Vegetarian Diets © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Populations consuming vegetarian and semi-vegetarian diets have lower rates of several chronic diseases that typically plague Western countries, including heart disease, hypertension, diabetes, and certain cancers. This is true of vegetarians living in Western countries and of populations consuming© Jones plant-based & Bartlett diets in developingLearning, countries. LLC Migration studies indicate© these Jones differences & Bartlett Learning, LLC are dueNOT to environmental FOR SALE factors. OR TheDISTRIBUTION incidence of heart disease and many cancersNOT increases FOR when SALE OR DISTRIBUTION people from countries where plant-based diets are consumed relocate to countries with diets pre- dominantly based on animal products. Similarly, when people in developing countries become more affluent and begin to add more animal products to their diet, rates of chronic disease increase.1,2 © Jones & BartlettMuch of theLearning, available information LLC about health effects ©of Jonesvegetarian & diets Bartlett comes fromLearning, two LLC NOT FOR largeSALE prospective OR DISTRIBUTION epidemiologic studies. The Adventist HealthNOT Study FOR (AHS)-1 SALE is ORa cohort DISTRIBUTION of 34,192 California Seventh-day Adventists (SDAs) that began in 1974–1976. The European Pro- spective Investigation into Cancer and Nutrition-Oxford (EPIC-Oxford) in the United Kingdom has 65,429 participants and oversampled for vegetarians. In addition, a second study of Adven- tists, the AHS-2, began in 2002 and had enrolled 96,194 participants as of 2007. It includes © Jones & Bartlett Learning,subjects from LLC all 50 states and Canada and© Joneshas provided & Bartlett some preliminary Learning, cross-sectional LLC data NOT FOR SALE OR DISTRIBUTIONbased on enrollment questionnaires. NOT FOR SALE OR DISTRIBUTION Smaller cohorts that also enrolled vegetarians were the Health Food Shoppers Study, the Oxford Vegetarian Study, both in the United Kingdom, and the Heidelberg Vegetarian Study in Germany. Data from the AHS-1 showed that SDAs had longer life expectancies compared to the general population,© Jones which & was Bartlett attributable Learning, to a healthy LLClifestyle that includes exercise, tobacco© Jones avoidance, & Bartlett Learning, LLC and healthfulNOT FOR diet, SALEand also ORthat amongDISTRIBUTION the study participants, Adventist vegetariansNOT FOR had even SALE OR DISTRIBUTION greater life expectancy than nonvegetarians.3 However, results from the EPIC-Oxford and the Oxford Vegetarian Study showed that, although British vegetarians were found to have low mor- tality rates compared to the general population, there was no difference in mortality between vegetarians and other study participants who had healthful lifestyles, although mortality from © Jones &ischemic Bartlett heart Learning, disease was 19% LLC lower among the vegetarians.©4 IdentifyingJones & precisely Bartlett which Learning, dietary LLC NOT FOR SALE OR DISTRIBUTION 13 NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE03_79764_02_013_062.indd OR DISTRIBUTION 13 NOT FOR SALE OR DISTRIBUTION 6/15/10 11:33:16 AM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 14 CHAPTER 2 HEALTH CONSEQUENCES OF VEGETARIAN DIETS factors affect© Jonesdisease rates & Bartlett of vegetarians Learning, is difficult LLCbecause so many differences exist© Jones between & Bartlett Learning, LLC vegetariansNOT and nonvegetarians. FOR SALE It ORis therefore DISTRIBUTION instructive to consider some of these dietaryNOT differ- FOR SALE OR DISTRIBUTION ences within the context of what is known about the relationship between specific dietary com- ponents and disease risk. © JonesDIFFERENCES & Bartlett IN Learning,DIETARY COMPONENTS LLC OF VEGETARIAN© Jones & Bartlett Learning, LLC AND NONVEGETARIAN DIETS NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Dietary Fat and Cholesterol Differences in fat intake between vegetarians and nonvegetarians are not as striking as com- monly thought. In the United States, fat intake has declined and now averages about 34% of 5,6 © Jones & Bartlett caloricLearning, intake. LLC By comparison, lacto-ovo vegetarians© Jones and vegans & Bartlett consume dietsLearning, that are 28–34% LLC and 25–30% fat, respectively, although there is considerable variation among studies (Appendix A). NOT FOR SALE OR DISTRIBUTIONFrom studies involving direct comparisons (AppendixNOT FOR A; Table SALE 2-1), OR it is clearDISTRIBUTION that omnivores consume considerably more saturated fat than vegetarians, although both lacto-ovo vegetarians and omnivores consume more saturated fat than polyunsaturated fat. In contrast, vegans con- sume more polyunsaturated fat than saturated fat. Their lower saturated fat content is likely part of the explanation© Jones for the & reducedBartlett rates Learning, of coronary heart LLC disease (CHD) seen in some© vegetarians Jones & Bartlett Learning, LLC and vegans, although recent research has raised some uncertainty about the relationship between saturated fatNOT intake FOR and CHD SALE risk. OR7 DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Cholesterol intake is also lower among vegetarians. Data from the National Health and Nutri- tion Examination (NHANES)-III indicate average U.S. cholesterol intake is about 300 mg/d.5 Lacto-ovo vegetarian cholesterol intake is typically between 150 and 300 mg/d, and strict vegan © Jonesdiets & contain Bartlett no cholesterol. Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Dietary Fiber and Carbohydrate Intake Fiber intake differs markedly between vegetarians and nonvegetarians. Older dietary surveys indicated that Americans consumed as little as 10 to 12 g of fiber/d,8 but more recent data sug- gest fiber intake may be as high as 17 g/d for men and 16 g/d for women; these figures are more © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Table 2-1 Comparison of Vegetarian and Nonvegetarian Intakes of Protein, Fat, Carbohydrate, Cholesterol, and Fiber Nutrient Nonvegetarian Lacto-Ovo Vegetarian Vegan Fat (% total© Jones calories) & Bartlett Learning,34 LLC 28–34 © 25–30Jones & Bartlett Learning, LLC CholesterolNOT (total FOR grams) SALE OR DISTRIBUTION300 150–300 NOT0 FOR SALE OR DISTRIBUTION Carbohydrate (% total calories) Ͻ50 50–55 50–65 Dietary fiber (total grams) 15–20 20–35 25–50 Protein (% total calories) 14–18 12–14 10–12 © Jones Animal& Bartlett protein (% Learning, total protein) LLC 60–70 ©40–60 Jones & Bartlett0 Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE03_79764_02_013_062.indd OR DISTRIBUTION 14 NOT FOR SALE OR DISTRIBUTION 6/15/10 11:33:17 AM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Cardiovascular Disease 15 consistent© Jones with the & data Bartlett in Appendix Learning, A.9,10 Nevertheless, LLC lacto-ovo vegetarians generally© Jones consume & Bartlett Learning, LLC betweenNOT 50% FOR and 100%SALE more OR fiber DISTRIBUTION than nonvegetarians, and vegans consumeNOT more FORfiber than SALE OR DISTRIBUTION lacto-ovo vegetarians. The U.S. Dietary Guidelines recommend 14 g fiber/1000 kcal.11 Not surprisingly, vegetarian diets are higher in carbohydrate than omnivore patterns. Vegans consume roughly 50–65% of their calories in the form of carbohydrate, lacto-ovo vegetarians about 50–55%, and omnivores generally Ͻ50% (Appendix A). © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORProtein SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Protein accounts for approximately 15% of calories in the diet of Western omnivores. Ameri- cans typically consume 50–100% more than the adult protein recommended dietary allowance (0.8 g/kg body weight). Lacto-ovo vegetarians consume diets containing between 12% and 14% © Jones & Bartlett Learning,protein, and LLC vegan diets are between 10%© and Jones 12% protein& Bartlett (Appendix Learning, A). Clearly, LLC the type of NOT FOR SALE OR DISTRIBUTIONprotein consumed also differs. American omnivoresNOT FOR derive SALE about twoOR thirds DISTRIBUTION of their protein from animal foods; this has changed from the early 20th century when only half of dietary protein was derived from animal sources.12 In contrast to the omnivore diet, about 40–60% of the protein in lacto-ovo vegetarian diets is derived from animal products, whereas vegans consume plant protein only.13–15 In a sample of Ͼ6000 individuals who participated in the NHANES-III survey, Smit et al found© Jones that animal & Bartlett protein intake Learning, was directly LLC associated with