Zespri ® Scientific Nutrition & Health Attributes Pack of Kiwifruit Index

® Zespri Research...... 03 • Introduction ...... 05 • Zespri® Scientific Activities...... 05 • Strategic Research and Scientific Advisory Steering Group ...... 06 • Regulatory Relationships...... 07 • International Research Partnerships...... 07

Nutrient Richness...... 09 • Zespri® Kiwifruit Consistently Rank as One of the Most Nutrient Rich Fruits...... 11 • Kiwifruit Has a High Vitamin C Content ...... 15 • Kiwifruit Facilitates Iron Uptake ...... 16 • Kiwifruit is Rich in Fibre ...... 16 • Kiwifruit is a Good Source of Potassium ...... 17 • Kiwifruit Has a High Level and Variety of Antioxidant Vitamins and Phytonutrients ...... 18 • Kiwifruit is a Natural Source of Folate ...... 19 • Conclusions ...... 20 • References ...... 21

Digestive Health ...... 23 • Common Digestive Disorders Cause Significant Discomfort ...... 25 • Kiwifruit Components Effect on Gastric and Intestinal Digestion ...... 26 • Kiwifruit as a Digestive Aid: What is the Evidence? ...... 29 • Upcoming Research ...... 35 • Conclusions ...... 36 • References ...... 37

Vitamin C and Health ...... 39 • Vitamin C is an Essential Vitamin that Cannot Be Synthesised by the Human Body ...... 41 • Vitamin C Has an Important Role in Human Metabolic Processes ...... 42 • How Much Vitamin C Do We Need? ...... 43 • One Zespri® Kiwifruit a Day Gives the Daily Requirement of Vitamin C ...... 44 • Zespri® Kiwifruit is Very Effective at Increasing Plasma Levels of Vitamin C ...... 44 • Kiwifruit and Vitamin C-Related Health: What is the Evidence? ...... 45 • Upcoming Research ...... 55 • Conclusions ...... 56 • References ...... 57

Metabolic Health ...... 59 • Kiwifruit Has a Low Glycaemic Index ...... 61 • Kiwifruit Modulates Carbohydrate Digestion and Absorption ...... 62 • The Glycaemic Response Per Kiwifruit Is Low ...... 62 • Kiwifruit Can Help Manage Blood Sugar Levels in People With Diabetes ...... 63 • Kiwifruit Affects Gut Microbiota ...... 63 • Kiwifruit and Metabolic Health: In Vitro and In Vivo Studies ...... 63 • Upcoming Research ...... 65 • Conclusions ...... 66 • References ...... 67

1 Research ® Nutrition Zespri Zespri® and HealthResearch Attributes of Kiwifruit3 Zespri® Research

Introduction

Welcome to the Zespri® Scientific Pack, where you will find a high-quality body of evidence on the nutrition and health attributes of kiwifruit. At Zespri® we believe in the integrity of our product, and in order to build trust with our loyal consumers, we know the importance of demonstrating the scientific efficacy of our kiwifruit.

This Scientific Pack provides authorities, health advocates and the scientific community with an overview of evidence-based findings on the nutritional profile and health benefits associated with consumption of kiwifruit, including underpinning fundamental science explaining the mechanisms of observed outcomes. The pack includes current and emerging data in four core areas:

• Nutrient Richness • Digestive Health • Vitamin C and Health • Metabolic Health

Zespri® Scientific Activities

In 2008, Zespri® put in place a world-class health and nutrition research programme around the health benefits of kiwifruit by joining forces with the Riddet Institute to form the Strategic Research and Scientific Advisory (SRSA). The Riddet Institute is a New Zealand government- funded Centre of Research Excellence with a widely acknowledged international standing.

The main aims of the SRSA are to ensure that Zespri® research projects are independently reviewed by experienced and respected scientists in the nutrition and health field. The projects are considered for their fit with the overarching Zespri® Health Strategy and the SRSA also reviews the scientific protocols and ensures that the research provider is the best science team for the required work. The composition of the steering group has been carefully put together to cover the range of activities that we are working on, such as laboratory-based research, animal model research and human clinical trials.

5 Strategic Research and Scientific Advisory Steering Group

Dr Juliet Ansell Dr Abby Thompson Lynley Drummond DPhil (Oxon): PhD, BTech: Director of BSc: Strategy, Innovation Innovation Leader Health Riddet Innovation at & Science advisor & Nutrition at Zespri Massey University at Drummond International Ltd Food Advisory Ltd

Dr Jocelyn Eason Professor Distinguished BSc, PhD, MBA: General Richard Gearry Professor Paul Moughan Manager Food Innovation MBChB, FRACP, PhD: BAgrSc (Hons), PhD, DSc, at Plant & Food Research Professor of Medicine at the Hon DSc, FRSNZ, FRSC: University of Otago Co-director of the Riddet Institute at Massey University

Dr Véronique Parmentier Professor Carol Ward BSc, PhD: David Richardson General Manager Global Health Marketing BSc, MSc, PhD, FIFST, FRSM: Marketing at Zespri Manager at Zespri Specialist Consultant in International Ltd International Ltd Nutrition and Food Science

6 Although all projects pass by the SRSA board for scientific merit and strategic fit, the ongoing clinical trial project management and troubleshooting is carried out by a smaller team. This consists primarily of Professor David Richardson, Professor Richard Gearry, Lynley Drummond and Dr Juliet Ansell, with principal investigators for each country involved in protocol development and ongoing trial management.

Figure 1. Overarching Zespri® Business Strategy

Scientific Business Research Provider Scientific Peer Review Approval Engagement Quarterly meetings Bi-monthly review of new projects for Proposal sought by of the SRSA board financial approval Innovation Leader: review on merit with consideration of non-competitive. and strategic fit. strategic priorities and commercial return.

Zespri® has established a number of research partnerships in New Zealand and internationally, who provide world class input into nutrition and health science.

Regulatory Relationships

Zespri® works in accordance to European Food Safety Authority (EFSA) guidelines and the Australia New Zealand Food Standards Code and in conjunction with the Ministry for Primary Industries, New Zealand.

International Research Partnerships

7 Nutrition

Nutrient Nutrient Richness and HealthRichness Attributes of Kiwifruit Nutrient Richness

Zespri® Kiwifruit Consistently Rank as One of the Most Nutrient Rich Fruits

Kiwifruit is known as a nutritionally dense fruit based on the level of nutrients present (Table 1)1. With nutrient adequacy scores of 18.8 and 11.4, Zespri SunGold and Zespri Green kiwifruit, respectively, have the highest nutritional value score among the most popular fruit varieties (Breakout box 1; Figure 1). Kiwifruit are also relatively low in calories and consequently their consumption is appropriate in weight control diets.

11 Table 1. Nutrient content of Zespri SunGold and Zespri Green kiwifruit

Nutrient Units/100 g Zespri® Green* Zespri® SunGold** Edible Flesh

Proximates Water g 83.5 82.4 (EC) EU † Energy kcal 81 79 (USDA) US † Energy kcal 57 63 Protein g 1.2 1.02 Total lipid (fat) g 0.7 0.28 Ash g 0.65 0.47 Carbohydrate, available g 9.1 15.8 Fibre, total dietary g 3 1.4 Sugars, total g 8.8 12.3 Minerals Calcium, Ca mg 27 17 Iron, Fe mg 0.2 0.21 Magnesium, Mg mg N/A 12 Phosphorus, P mg 34 25 Potassium, K mg 300 315 Sodium, Na mg 2.3 3 Zinc, Zn mg 0.1 0.08 Copper, Cu mg N/A 0.151 Manganese, Mn mg N/A 0.048 Selenium, Se µg 0.6 0.4 Vitamins Vitamin C, total ascorbic acid mg 85.1 161.3 Vitamin B1 - thiamin mg 0 0 Vitamin B2 - riboflavin mg 0.05 0.074 Vitamin B3 - niacin mg 0.83 0.231 Vitamin B5 - panthothenic acid mg N/A 0.12 Vitamin B6 - pyrridoxine mg 0.07 0.079 Vitamin B9 - folate (DFE) µg 38 31 Choline mg N/A 1.9 Vitamin B12 µg 0 0.08 Vitamin A µg 9 N/A Vitamin A, retinol activity equivalents µg N/A 1 (RAE) Vitamin A IU N/A 23 Vitamin E - a-tocopherol mg 0.86 1.4 Vitamin K µg N/A 6.1

Other Carotene, beta µg 54 14 Lutein + zeaxanthin µg N/A 24 NUTRIENT ADEQUACY SCORE 11.4 18.8 NUTRIENT DENSITY /100 kcal 20 29.8 GLYCAEMIC INDEX 39 38

Sources of data * Crop & Food Research, New Zealand Nutrient composition of New Zealand Zespri Green kiwifruit, 2015. ** Combined data from NVIG2010, Japan market analysis 2010 and ZESPRI analysis 2011. † There are a number of equations to calculate energy as noted by the European Commission (2014) and USDA (2009). The first line in the table refers to the European Commission legislature that calculates energy as total carbohydrate plus fibre http://ec.europa.eu/food/safety/labelling_nutrition/labelling_legislation/index_en.htm The second line in the table refers to USDA legislature that calculates energy as total carbohydrate by difference minus insoluble fibre http://www.fda.gov/food/guidanceregulation/guidancedocumentsregulatoryinformation/labelingnutrition/ ucm2006828.htm Nutrient Adequacy Score and Nutrient Density calculated based on the methods of Darmon N, et al. A Nutrient Density Standard for Vegetables and Fruits: Nutrients per Calorie and Nutrients per Unit Cost. J Am Diet Assoc 2005:105:1881-7

12 Figure 1. Zespri® kiwifruit has the highest nutrient adequacy score of commonly eaten fruits2

Zespri SunGold Kiwifruit 18.8

11.4 Zespri Green Kiwifruit

Orange 8.1

8.0 Strawberry

Lemon 7.0

4.9 Banana

Pomegranate 4.8

3.7 Cranberry

Melon 3.6 Nutrient adequacy score Nutrient

2.9 Blueberry

Grape 2.4

2.1 Pear

Watermelon 2.1

1.8 Apple

Based on the method of Darmon N, et al (2005)2

13 Breakout box 1: Nutrient adequacy score

The nutrient adequacy of a certain food refers to how many nutrients it provides relative to its weight. This is different to the nutrient density of a food, which refers to how many nutrients it provides relative to the number of calories it contains.

A nutrient adequacy score is determined as the mean percentage of daily values (amount per 100 g / recommended dietary allowance [RDA]) of 17 selected nutrients, including: protein, fibre, calcium, iron, magnesium, potassium, zinc, vitamin C, thiamin (vitamin B1), riboflavin (vitamin B2), niacin, pantothenic acid, pyridoxine (vitamin B6), folic acid, vitamin B12, vitamin A and vitamin E.

The high amount of vitamin C in kiwifruit is the primary driver of its high nutrient adequacy score1. Other key nutrients include fibre, folate, potassium and vitamin 1E . Kiwifruit also contains a wide variety of antioxidants, phytonutrients and enzymes with known digestive benefits, and is low in calories, containing just 57 kcal/100 g1. The combination of all these unique attributes works within the body to provide significant health benefits (Figure 12) .

Figure 2. Health benefits of kiwifruit

FIBRE FOLATE

• Pregnancy • Digestive • Reduces tiredness health B9 and fatigue

VITAMIN C POTASSIUM • Immune system function • Reduces tiredness • Heart activity and C and fatigue K fluid balance • Helps normal collagen formation

PHYTONUTRIENTS & ANTIOXIDANTS LOW GLYCAEMIC INDEX

• Defence against • Glucose cell damage tolerance • Cardiovascular health GI

14 Kiwifruit Has a High Vitamin C Content

Zespri® kiwifruit is one of the best sources of vitamin C among fruits and vegetables (Figure 3). Zespri SunGold kiwifruit contains 161.3 mg/100 g of vitamin C, almost three times the amount of vitamin C found in oranges and strawberries, traditionally known as good sources of vita- min C, while Zespri Green kiwifruit contains 85.1 mg/100 g3. More information on the role of vitamin C in kiwifruit can be found in the Vitamin C and Health section of this Scientific Pack.

Figure 3. Graph comparing the vitamin C content of various fruits with Zespri® kiwifruit3

200

161.3 150

100 85.1 84.0 EU RDA 60.9 58.8 100% Vitamin C (mg/100 g) Vitamin 53.2 47.8 50 36.4 26.7 18.0 19.7 EU 8.7 14 9.7 8.1 10.2 4.6 4.0 4.3 RDA 0 15%

Pears Apples Grapes Melons Papaya Bananas Oranges Mangoes LongansDurians Blueberries Pineapples Cranberries MandarinesStrawberries Zespri Green** WatermelonsPomegranates Zespri SunGold*

* USDA Nutrient Database 2015 (Release 28) ** New Zealand FOODfiles 2014 Version 01

15 Kiwifruit Facilitates Iron Uptake

High levels of vitamin C in kiwifruit can improve iron uptake

Poor iron status remains one of the most common micronutrient concerns globally. In a study of individuals with low iron status (serum ferritin [SF] ≤25 μg/l and haemoglobin [Hb] ≥115 g/L), eating kiwifruit with an iron-fortified breakfast cereal was found to increase iron status4, 5. In this study, 89 healthy women were randomised to receive iron-fortified breakfast cereal, milk and either two Zespri Gold kiwifruit or one banana at breakfast every day for 16 weeks. After 16 weeks, median serum ferritin significantly increased from 17.0 μg/l at baseline to 25.0 μg/l, compared to the banana group who had a median serum ferritin of 16.5 μg/l at baseline that rose to 17.5 μg/l at the end of the study (p<0.001)5. Importantly, the 10.0 μg/l increase in serum ferritin in the women who ate kiwifruit increased levels to within the normal reference range of 20–160 mg/l5. Additionally, median soluble transferrin receptor concentrations significantly decreased by –0.5 mg/l for kiwifruit versus 0.0 mg/l for banana (p=0.001)5.

Kiwifruit is Rich in Fibre

Kiwifruit has been found to improve various digestive functions due to its fibre content (1.4–3 g/100 g; Figure 4). Kiwifruit fibre consists of both soluble and insoluble fibre at a ratio of approximately 1:4 in Green kiwifruit and 1:3 in SunGold6. The soluble fibre fraction contains almost exclusively pectic polysaccharides that have the ability to retain water and form gels. This increases the size and softness of the stools and helps stimulate bowel movements, faci- litating intestinal transit through the digestive system7. The insoluble fibre fraction is mostly cellulose and hemicelluloses, which make up the structural parts of plant cell walls, with small amounts of pectin. A major role of insoluble fibre is to add bulk to the stools, aiding movement through the digestive tract7. More information on the role of fibre in kiwifruit can be found in the Digestive Health section of this Scientific Pack.

Figure 4. Fibre content of Zespri® kiwifruit compared to other fruit3

5 4.0 3.8 4 3.6 3.1 3.0 3 2.4 2.6 2.4 2.4 2.0 1.8 1.8 2 1.6 1.4 1.4 1.1 0.9 1 0.8 0.4 Total fibre content (g/100 g) fibre Total 0

Pears Apples Grapes Melons Papaya Bananas Oranges Mangoes LongansDurians Blueberries Pineapples Cranberries MandarinesStrawberries Zespri Green** WatermelonsPomegranates Zespri SunGold*

* USDA Nutrient Database 2015 (Release 28) ** New Zealand FOODfiles 2014 Version 01

16 Kiwifruit is a Good Source of Potassium

Potassium is an important mineral for the development of many different body functions8. In particular, it:

• Contributes to the normal function of the nervous system. • Is necessary for muscular contraction. • Contributes to the maintenance of normal blood pressure.

Fresh foods such as fruits, green vegetables and cereals or wholemeal bread are generally high in potassium and low in sodium. The daily recommended value for potassium is 3500 mg3. Zespri® kiwifruit contains 301–315 mg/100 g potassium, which is roughly equivalent to the amount of potassium in a banana (Figure 5).

Figure 5. Potassium content of Zespri® kiwifruit compared to other fruit3

500 436

400 358

315 301 EU 300 266 RDA 15% 228 236 191 181 182 200 166 168 153 Potassium (mg/100 g) Potassium 116 107 112 109 100 80 77

0

Pears Apples Grapes Melons Papaya Bananas Oranges Mangoes LongansDurians Blueberries Pineapples Cranberries MandarinesStrawberries Zespri Green** WatermelonsPomegranates Zespri SunGold*

* USDA Nutrient Database 2015 (Release 28) **New Zealand FOODfiles 2014 Version 01

17 Kiwifruit Has a High Level and Variety of Antioxidant Vitamins and Phytonutrients

Antioxidants are substances that may prevent or delay some types of cell damage9,10. They do this by blocking some of the damage caused by free radicals, unstable molecules created every day during normal metabolism that damage DNA.

Kiwifruit contains a wide range of natural antioxidants, such as vitamin C, vitamin E, polyphenols and flavonoids (compounds derived from polyphenols)1. Research has shown a significant increase in plasma antioxidant levels following the consumption of kiwifruit compared to the consumption of other fruits and foods11. While vitamin C is generally regarded as the most important antioxidant of kiwifruit, vitamin E and the polyphenols and flavonoids present in both Zespri Green and Zespri SunGold kiwifruit also have an antioxidant effect. There is strong evidence showing that eating foods with polyphenolic compounds contributes to good overall health12.

Vitamin E is the generic term for a group of eight plant-derived, fat-soluble and structurally related compounds belonging to two main families – the tocopherols and tocotrienols. Natural and naturally derived tocopherols occur only in a single form (RRR, also known as alpha- or delta-tocopherol). Vitamin E is the body’s primary lipid-soluble antioxidant defence against free-radical-induced cell damage13.

Vitamin E levels in Zespri SunGold are relatively high compared to other fruits, at 0.9–1.4 mg/100 g. This is important because in general, fruit are poor sources of vitamin E, with the exception of avocado. However, unlike avocado, kiwifruit is one of the few low-fat sources of vitamin E.

Phytonutrients are bioactive plant-derived compounds that are associated with positive health effects. Phenolic phytochemicals are the largest category of phytochemicals; the three most important groups of dietary phenolics are flavonoids, phenolic acids, and polyphenols14. Kiwifruit contains various phytochemicals, such as phenolic acids and flavonols,13 which are thought to protect DNA in the nucleus of human cells from oxygen-related damage via a dual protective role: decreasing DNA oxidation damage and enhancing removal of the damage that does occur1.

18 Kiwifruit is a Natural Source of Folate

Folate is an essential nutrient for cellular growth and development, and is vital for the formation of the erythrocytes (red blood cells) that transport oxygen, iron and other minerals15. Folate performs important functions in the healthy body, and sufficiently high levels are needed before and during pregnancy. It is also vital for infant growth. Some of its contributions are as follows7, 15:

• Growth of tissue during pregnancy • Normal formation of amino acids • Normal formation of blood cells • Normal formation of homocysteine • Normal psychological function • Reduction of tiredness and fatigue • Process of cell division

As cooking destroys folate, fresh kiwifruit is a good source of folate, compared to for example cooked green vegetables. The daily recommended value for folate is 400 μg. During pregnancy, it is very difficult to meet folate requirements with food alone. Zespri® kiwifruit contains 31–38 μg/100 g folate, making it a useful complement to folic acid supplements in pregnant women (Figure 6).

Figure 6. Folate content of Zespri® kiwifruit compared to other fruit3

50

43 40 38.2 38.0 37.0

31 30.0 EU 30 RDA 24.0 15%

20.0 19.0 20 18.0 16.0 Folate content (µg/100 g) Folate 10 6.0 7.0 3.0 4.0 3.0 1.0 0

Pears Apples Grapes Melons Papaya Bananas Oranges Mangoes Blueberries Pineapples Cranberries MandarinesStrawberries Zespri Green** WatermelonsPomegranates Zespri SunGold*

* USDA Nutrient Database 2015 (Release 28) ** New Zealand FOODfiles 2014 Version 01

19 Conclusions

• Zespri® kiwifruit is consistently one of the most nutrient-rich fruit available, driven primarily by the high vitamin C content. The high levels of vitamin C in kiwifruit can assist the body’s uptake of iron.

• Zespri® kiwifruit contains high level and variety of antioxidants and phytonutrients, such as vitamin C, vitamin E, polyphenols and flavonoids. These compounds reduce the amount of oxidative damage to the cells of the body and improve the repair of damaged DNA caused by free radicals and oxidative stress.

• Zespri® kiwifruit is a good source of potassium.

• Zespri® kiwifruit is rich in fibre, which contributes to good digestive health improving bowel habits and stimulating the growth of beneficial bacteria in the gut.

• Zespri® kiwifruit is a natural source of folate.

• The combination of vitamins, minerals, laxative effects and benefits for improving iron uptake makes kiwifruit an excellent fruit during pregnancy.

20 References

1. Boland M, Moughan PJ. Advances in food and nutrition research. 9. Ginter E, Simko V, Panakova V. Antioxidants in health and Nutritional benefits of kiwifruit. Waltham, MA: Elsevier Inc; disease. Bratisl Lek Listy. 2014;115:603-6. 2013. 10. National Institutes of Health. Antioxidants and health: An 2. Darmon N, Darmon M, Maillot M, Drewnowski A. A nutrient introduction. 2015. density standard for vegetables and fruits: nutrients per calorie 11. Prior RL, Gu L, Wu X, Jacob RA, Sotoudeh G, Kader AA, Cook and nutrients per unit cost. J Am Diet Assoc. 2005;105:1881-7. RA. Plasma antioxidant capacity changes following a meal as 3. USDA. USDA national nutrient database for standard reference a measure of the ability of a food to alter in vivo antioxidant (release 28). 2015. status. J Am Coll Nutr. 2007;26:170-81. 4. Beck K, Conlon C, Kruger R, Coad J, Stonehouse W. The effect of 12. Kim EY, Ham SK, Shigenaga MK, Han O. Bioactive dietary gold kiwifruit consumed with an iron fortified breakfast cereal polyphenolic compounds reduce nonheme iron transport meal on iron status in women with low iron stores: A 16 week across human intestinal cell monolayers. J Nutr 2008;138:1647- randomised controlled intervention study. BMC Public Health. 51. 2010;10:36. 13. Fiorentino A, D’Abrosca B, Pacifico S, Mastellone C, Scognamiglio 5. Beck K, Conlon CA, Kruger R, Coad J, Stonehouse W. Gold M, Monaco P. Identification and assessment of antioxidant kiwifruit consumed with an iron-fortified breakfast cereal meal capacity of phytochemicals from kiwi fruits. J Agric Food Chem. improves iron status in women with low iron stores: A 16-week 2009;57:4148-55. randomised controlled trial. Br J Nutr. 2011;105:101-9. 14. King A, Young G. Characteristics and occurrence of phenolic 6. The New Zealand Institute for Plant & Food Research Limited. phytochemicals. J Am Diet Assoc. 1999;99:213-8. (2015). New Zealand Food Composition Database: New Zealand 15. Bailey LB, Stover PJ, McNulty H, Fenech MF, Gregory JF 3rd, Mills FOODfiles 2014 Version 01. Retrieved March 30, 2015 from http:// JL, Pfeiffer CM, Fazili Z, Zhang M, Ueland PM, Molloy AM, Caudill www.foodcomposition.co.nz/foodfiles. MA, Shane B, Berry RJ, Bailey RL, Hausman DB, Raghavan R, 7. Sims IM, Monro JA. Fiber: Composition, structures, and Raiten DJ. Biomarkers of nutrition for development-folate functional properties. Adv Food Nutr Res. 2013;68:81-99. review. J Nutr. 2015;145:1636S-1680S. 8. European Commission. EU register on nutrition and health claims (2012).

21 Nutrition Digestive Health

and Health Digestive Health Attributes of Kiwifruit Digestive Health

Common Digestive Disorders Cause Significant Discomfort

Gastrointestinal disorders are common conditions worldwide in adults and children, and can severely affect the individual’s quality of life and feeling of general wellbeing1. They may affect the upper gastric part of the digestive system or the lower intestinal area, and can cause a range of symptoms (Figure 1). These disorders generally result from lifestyle factors such as diet, hydration and exercise, from chronic illnesses such as diabetes, and from aging1. Current interventions for gastrointestinal conditions include lifestyle and dietary modifications as well as pharmacologic intervention, which may cause side-effects1.

Figure 1. Common gastrointestinal disorders

Upper gastrointestinal disorders

• Gastric reflux • Stomach ache • Delayed gastric emptying • Nausea • Vomiting

STOMACH Lower gastrointestinal disorders COLON • Constipation • Indigestion INTESTINES • Bloating • Diarrhoea

25 Kiwifruit Components Effect on Gastric and Intestinal Digestion

Green kiwifruit are an excellent source of vitamins (A, C, and E), minerals (potassium), fibre and certain bioactive components, such as polyphenols and enzymes2. Kiwifruit has been found to improve various digestive functions at both the gastric and intestinal level. This is due to their relatively high fibre content (3 g/100 g in raw Zespri Green kiwifruit and 1.4 g/100 g in raw Zespri SunGold kiwifruit) and the presence of a natural digestive enzyme unique to kiwifruit known as actinidin, which breaks down proteins and facilitates gastric digestion2.

The substances found in kiwifruit have been shown to promote the effective digestion of dietary protein, increase faecal bulking and softness, and enable better lubrication, assisting the propulsion of contents along the colon (Figure 2)3. In addition to positive effects on gastric and intestinal digestion, kiwifruit are also associated with beneficial changes in gut microbiota (see Breakout box 1 and 2)2,4.

Figure 2. Digestive benefits of kiwifruit

Upper gastrointestinal tract

• Facilitates gastric digestion • Reduces glucose absorption rate • Potentially reduces symptoms such as nausea and vomiting

Lower gastrointestinal tract

• Improves intestinal habits, reducing constipation • Creates positive changes in intestinal enzymes that can serve as a natural defence • Encourages the growth of beneficial bacteria, which inhibit harmful bacteria

26 Breakout box 1: Microbiota

Human gut bacteria (microbiota) have co-evolved with us metabolically to live symbiotically and share the workload of extracting energy and nutrients from the diet. A healthy balance of gut microbiota is therefore essential for the breakdown of foods and for the production of vitamins. The dietary fibre and polyphenols found in kiwifruit can be degraded by various members of the gut microbiota and result in beneficial effects (Figure 3)2, 4-6. These gut microbiota can also affect the structure and function of the mucosal barrier in the colon, which prevents the influx of water soluble bacterial products and toxins from the colon into the blood7.

Figure 3. The role of gut microbiota in the breakdown of food

Fibre Polyphenols Carbohydrates

Gut microbiota

Other metabolites

Polyphenol Short chain Oligosaccharides metabolites fatty acids

Health benefits • Energy and nutrients for colonic cells and other good bacteria • Secretion of immune effector molecules which regulate proper immune function

27 Breakout box 2: Prebiotics

Prebiotics are food ingredients, generally of plant origin, that cannot be broken down by the human digestive system, such as soluble fibre. Instead, various members of the gut microbiota can degrade them. The breakdown of prebiotics selectively stimulates the growth or activity of ‘good’ bacteria in the colon. These bacteria include lactobacilli and bifidobacteria species, which are commonly included in probiotic foods and supplements.

What is the role of fibre in digestive health?

Fibre in kiwifruit is made up of soluble components (e.g. pectin) and insoluble components (e.g. hemicelluloses and celluloses, which make up cell walls)8. Soluble fibre has the ability to retain water and form gels, which increases the size and softness of the stools, and aids stimulation of peristaltic movements8. Insoluble fibres also enhance digestion by adding bulk to the stools, aiding movement through the digestive tract8.

There is some evidence to suggest that as the kiwifruit ripens, there is increasing solubilisation of insoluble fibre within the cell walls of kiwifruit. This results in a unique and greatly increased ability to hold water, causing a lubricating effect (Figure 4)9-11.

Figure 4. Water retention capacity of various fruit fibre8

14

12

10

8

6

g water / g sample g water 4

2

0 Wheat Beetroot Apple Orange Zespri bran fibre fibre fibre Green fibre

28 Collectively, these properties can help to improve the symptoms of constipation by8:

• Increasing the frequency of bowel movements • Improving the type of stools • Reducing the sensation of bloating • Increasing satisfaction when moving the bowels • Reducing the time of intestinal transit

In the upper gastrointestinal tract, these same properties of kiwifruit fibre act to reduce the rate of glucose absorption so that the glycaemic response is lower and blood sugar levels remain stable8. This is important for people who are wanting to maintain a healthy weight and prevent a progression into obesity, and eventually metabolic diseases such as type 2 diabetes. It also increases the sense of fullness, since the fibre swells by taking up water and acts to increase viscosity, and animal trials have also shown that eating kiwifruit can have a positive effect on the rate of gastric emptying12.

What is the role of actinidin in digestive health?

Actinidin has been shown to enhance protein digestion in the stomach and the small intestine13, 14, potentially allowing faster and more complete digestion of food proteins. This improved digestion results in:

• A reduced sensation of heaviness associated with protein-rich foods • Improved protein absorption • Improved digestive comfort

It is proposed that actinidin or other compounds in kiwifruit may also act as modulators of gastric motility. It has been observed that after protein digestion with actinidin, potentially bioactive peptides may be produced from the food proteins. However, it is unknown if these have any effect on gastric motility15.

Kiwifruit as a Digestive Aid: IN VITRO What Is the Evidence? STUDIES

Kiwifruit enhances protein digestion

In vitro studies have shown that actinidin, acting in combination with the gastric and intestinal enzymes pepsin and pancreatin, enhances protein digestion in both the stomach and the small intestine13, 14. In an in vitro study that examined the effect of actinidin on gastric protein digestion, a range of common protein sources derived from soy, meat, milk and cereals were incubated with a kiwifruit extract containing actinidin and pepsin at pH 1.9 (a simulation of gastric digestion in humans)13. Results showed that for milk, soy and meat protein sources, the presence of kiwifruit extract enhanced digestion to a greater extent than pepsin alone13.

In another in vitro study, a range of food proteins were studied to assess the proposition that actinidin influences the digestion of proteins in the small intestine14. Proteins from sources including soy, meat, milk, and cereals, were incubated in the presence or absence of actinidin with pepsin at stomach pH (stimulating gastric digestion) and then with added pancreatin at a pH to simulate small intestine digestion14. Actinidin was shown to influence the digestion patterns of each of the protein types to various extents. For some proteins, actinidin had little impact on digestion14. However, for whey, zein, collagen and wheat proteins, the presence of actinidin resulted in a substantially greater increase in digestion14.

29 Kiwifruit modifies colonic bacteria

A healthy balance of bacteria colonising the gastrointestinal tract (colonic microbiota) is essential for the breakdown and metabolism of foods as well as for the production of microbially synthesised vitamins. Interestingly, in vitro studies including some using a model gut system have demonstrated that components of kiwifruit are able to modulate colonic microbiota (Figure 5)5, 16-22. Nutrients known as polyphenolics may directly stimulate the growth of beneficial bacteria in the colon or act as antimicrobial agents against pathogens, while non-digestible polysaccharides (insoluble fibre) broken down by the microbiota may induce selective growth of beneficial bacteria19, 21.

Figure 5. Predominant bacterial groups after fermentation of kiwifruit and control food sources16

7.0

* 6.5

cfu/mL) * 10 * 6.0

5.5 spp. (log Bifidobacterium spp.

5.0 0 24 48 Time (h)

6.0 cfu/mL) 10 * 5.5 * *

5.0 spp. (log Lactobacillus spp. 0 24 48 Time (h)

Control Gold kiwifruit Green kiwifruit Inulin

The values represent mean log10 cfu/ ml±standard error, for 12 faecal fermentations, from the 10 donors. Means which were significantly different from the control at the corresponding time are marked with an asterisk

30 Kiwifruit modulates gut-mediated immune function

Kiwifruit has also been shown to enhance the production of antimicrobial peptides, an important part of the first line of defence at intestinal mucosal surfaces. Colonic epithelial cell studies in vitro have shown that human faecal microbial breakdown products from in vitro digested kiwifruit increased antimicrobial peptides human β-defensin 1 and 2 (HBD-1 and 2) production17. This could increase host protection against micro-organisms (see Breakout box 1).

Kiwifruit enhances protein IN VIVO digestion and gastric empting rate STUDIES

The effects of actinidin on protein digestion has also been replicated in vivo. A recent study in rats showed that actinidin from green kiwifruit significantly increased the gastric digestion of beef muscle protein, gelatin soy protein and gluten by 27–60%23. A separate study in growing rats showed increased gastric protein digestion with dietary actinidin from kiwifruit, and also demonstrated an accelerated gastric empting rate for several dietary protein sources24. Authors of this study conclude that it is likely that gastric empting rate is affected by gastric protein digestion24.

These results were confirmed by an in vivo study investigating the effect of dietary actinidin on gastric digestion of beef muscle proteins and gastric empting rate in pigs12. Use of a positive sample of added actinidin and a negative control of inactivated actinidin demonstrated a significant increase in gastric digestion with the active substance when consumed with meat (25% with actinidin, 17% without actinidin). This demonstrates conclusively that actinidin is responsible for the enhanced gastric hydrolysis of food proteins. Stomach emptying rate was also faster when green kiwifruit were consumed with meat (half life for dry matter was 137 min with actinidin versus 172 min without actinidin)12.

Kiwifruit beneficially modulates colonic microbiota

In vivo studies have shown that kiwifruit products that reach the colon result in changes in microbial growth and by-product formation (see Breakout boxes 1 and 2). An in vivo study in growing pigs found that animals who had eaten green kiwifruit had a significantly higher number of ‘good’ bacteria in the colon, leading to an improved intestinal environment4. These results were also replicated in another in vivo study, where rats who were fed a diet of green and gold kiwifruit for 6 weeks demonstrated significantly increased populations of ‘good’ bacteria2. As well as increased colonic microbiota, the rats were found to have improved colonic barrier function by increased mucin expression and improved immune cell stimulation. These in vitro changes in microbiota suggest that regular and consistent kiwifruit consumption could positively influence colonic health2.

31 Kiwifruit contributes to gastric comfort CLINICAL following protein ingestion STUDIES

In order to follow up on the promising results of the effects of actinidin on protein digestion in vitro and in vivo, a human clinical trial was conducted to examine its effect on gastric comfort following a protein meal25. In this study, 10 healthy adult males ate a meal of >400 g lean steak with 200 g kiwifruit containing either active or inactive actinidin. For all measures of gastric comfort (pain in upper abdomen, rumbling in stomach, bloating, belching, and flatulence) the men who ate the kiwifruit with active actinidin resulted in less symptoms25. For the symptom of ‘bloating’ this difference was statistically significant25.

Kiwifruit improves bowel functioning

There is growing evidence that kiwifruit has laxative properties, with several clinical studies demonstrating changes in bowel function in response to kiwifruit intake. In a study of 38 people, eating one kiwifruit/30 kg body weight for 3 weeks lead to increased frequency of defecation, higher volume of stool production, and greater softness of bowel motions26. In the second study, 33 chronically constipated patients were given two kiwifruit per day for 2 weeks27. Kiwifruit consumption significantly increased complete spontaneous bowel motion, improved transit time and rectal sensation, and decreased days of laxative use, compared with control subjects who were not given kiwifruit27. In the third study, the effect of kiwifruit intake on physiological bowel functions in 41 patients diagnosed with irritable bowel syndrome (IBS) was evaluated. Having eaten two kiwifruit per day for 4 weeks, participants significantly increased defecation frequency and decreased colon transit time28. Another study in a Mediterranean patient population suffering from functional constipation, demonstrated that the intake of three kiwifruit per day significantly improved the quality of evacuation (number of depositions, consistency and ease)29.

In a systematic review of clinical trials in which fresh kiwifruit were used for the treatment of constipation or functional bowel disorders, daily consumption of two kiwifruit was found to reduce symptoms associated with constipation, but did not adversely affect bowel habits in healthy non-constipated individuals (Table 1)30. Pooled data gave an increase in stool frequency of 1.6 per week when two kiwifruit were consumed, and a mean increase of 4.1 when three kiwifruit were consumed30.

Kiwifruit is suitable on a low FODMAP diet

Gastrointestinal symptoms associated with IBS can be triggered by poorly absorbed short chain carbohydrates. These carbohydrates can be fermented by bacteria in the colon releasing gases31-34 that stretches the bowel, causing bloating, wind and pain. They can also cause water to enter the colon, resulting in loose motions and diarrhoea. These short chain carbohydrates have been grouped together under the term FODMAPs which stands for Fermentable Oligo-, Di-, Mono- saccharides And Polyols (see Breakout box 3), and includes fructose (in excess of glucose), lactose, sugar polyols (sorbitol, mannitol), fructans and galacto-oligosaccharides (GOS). A diet low in FODMAPs is now often used to manage functional gastrointestinal symptoms in patients with IBS31, 35-38.

Interestingly, many fruits and vegetables are high in FODMAPs that can trigger abdominal symptoms in people with IBS. Kiwifruit, however, is a low FODMAP fruit39 as it has a balanced ratio of glucose to fructose, allowing fructose to be well absorbed. Kiwifruit can therefore be included as part of a low FODMAP diet for sufferers of IBS.

32 Table 1. Summary of findings from human clinical trials with fresh green kiwifruit 30

Reference Country Population Study Frequency Stool Ease/comfort Transit Side and daily group Quality ↑, SS from ↑, SS time effects intervention High ↑, NSS ↑, SS ↑, NSS ↓, SS Low ↑, NSS ? Not none ? Not able ? Not measured to assess measured

Chan et al. (2007): two Functional Zespri China constipation Green kiwifruit

Chang et al. Irritable (2010): two bowel Zespri Green Taiwan syndrome ? kiwifruit with constipation

Hiele (2010): three Functional Zespri Belgium constipation ? Green kiwifruit

Marzo & Cunillera (2015): Functional Spain three Zespri constipation ? Green kiwifruit

Ohsawa et al. (2010): two Prone to Zespri Japan constipation ? Green kiwifruit

Rush et al. (2002): pre trial, one New Zespri Green Healthy Zealand ? ? kiwifruit per 30 kg bodyweight

Rush et al. (2002): main trial, one New Healthy Zespri Green Zealand elderly ? kiwifruit per 30 kg bodyweight

SS= Statistically Significant | NSS = Not Statistically Significant

33 Breakout box 3: FODMAPs

FODMAPs (Fermentable Oligo-, Di-, Mono-saccharides And Polyols) are fermentable carbohydrates found in food that can cause digestive discomfort, especially for people with IBS. FODMAPs, which are poorly absorbed in the small intestine, pass through to the colon where they are fermented by bacteria, contributing to the production of gas. The FODMAPs are also highly osmotic and therefore attract water into the colon, which can alter how quickly the bowels move. These two processes can then trigger symptoms including abdominal pain, bloating, excessive wind, constipation or diarrhoea, or a combination of both.

Common high FODMAP foods include milk, apples, broccoli, wheat breads, cereals, pasta, avocados, pears, stone fruits, and mushrooms, among many more. A diet low in FODMAPs has been proven to be the most effective dietary therapy for IBS and symptoms of an irritable bowel31,35-38. The Monash University Department of Gastroenterology has developed a ‘Low FODMAP Certification Programme’ in order for people with medically diagnosed IBS to identify and select low FODMAP food choices. Certified low FODMAP products are listed in the Monash University low FODMAP diet booklet and app39. Kiwifruit is a low FODMAP food and listed as such in the FODMAP diet booklet and app.

34 Upcoming Research

Since early clinical studies were carried out in different countries and included different participant subgroups (e.g. in terms of age, health status, etc.), the lack of common protocol may have led to results that are not generalisable to the larger population. There was therefore a need for a large multinational study that enrolled a large group of participants with a range of digestive health conditions. A multi-country, randomised, cross-over, controlled, clinical intervention study is currently ongoing to evaluate the effect of Zespri Green kiwifruit on digestive and gut health function. The primary objective of this trial is to determine the efficacy of kiwifruit as a treatment for the relief of constipation and a reduction in gastrointestinal discomfort. In each participating country, 20 healthy people, 20 people with IBS with constipation (IBS-C) and 20 people with functional constipation (FC) will be recruited. The trial study design is presented below (Figure 6).

Figure 6 . Zespri® clinical intervention study design

2-week lead period

4-week kiwifruit 4-week psyllium intervention intervention

4-week washout period

4-week psyllium 4-week kiwifruit intervention intervention

2-week follow-up period

35 Conclusions

• Gastrointestinal issues are common conditions worldwide and can negatively affect an individual’s quality of life1.

• Green kiwifruit is a rich source of fibre, vitamins, minerals and certain bioactive components, and in vitro and in vivo studies have demonstrated beneficial effects on gastric and intestinal function2.

− The fibre content of kiwifruit can have a significant effect on digestion by increasing faecal bulking and softening, increasing lubrication of faecal matter and reducing glucose absorption rate, helping stabilise blood sugar levels.

− The enzyme actinidin, found uniquely in kiwifruit, improves digestive comfort by increasing the breakdown of proteins and facilitating gastric digestion.

− There is growing evidence that consumption of kiwifruit beneficially modulates the colonic microbiota, likely resulting in increased intestinal health and overall wellness.

• Clinical studies of kiwifruit have demonstrated positive results in the treatment of constipation in a range of adult populations, including healthy subjects, the elderly and patients with IBS.

− These studies suggest that daily consumption of kiwifruit may be effective for the treatment of constipation or functional bowel disorders, as well as an effective strategy to regulate the digestive system and enhance bowel movement satisfaction.

• Research on the digestive health benefits of kiwifruit is ongoing, with results of a multi-country, randomised, cross-over, controlled, clinical intervention study expected in 2016.

36 References

1. Ansell J, Butts CA, Paturi G, Eady SL, Wallace AJ, Hedderley 21. Ansell J, Parkar S, Paturi G, Rosendale D, Blatchford P. Modification D, Gearry RB. Kiwifruit-derived supplements increase stool of the colonic microbiota. Adv Food Nutr Res. 2013;68:205-17. frequency in healthy adults: A randomized, double-blind, 22. Carnachan SM, Bootten TJ, Mishra S, Monro JA, Sims IM. Effects placebo-controlled study. Nutr Res. 2015;35:401-8. of simulated digestion in vitro on cell wall polysaccharides from 2. Paturi G, Butts CA, Bentley-Hewitt KL, Ansell J. Influence of kiwifruit (Actinidia spp.). Food Chemistry. 2012;133:132-9. green and gold kiwifruit on indices of large bowel function in 23. Rutherfurd SM, Montoya CA, Zou ML, Moughan PJ, Drummond healthy rats. J Food Sci. 2014;79:H1611-20. LN, Boland MJ. Effect of actinidin from kiwifruit (Actinidia 3. Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. A diet deliciosa cv. Hayward) on the digestion of food proteins low in fodmaps reduces symptoms of irritable bowel syndrome. determined in the growing rat. Food Chem. 2011;129:1681-9. Gastroenterology 2014;146:67-75 e65. 24. Montoya CA, Hindmarsh JP, Gonzalez L, Boland MJ, Moughan 4. Han KS, Balan P, Molist Gasa F, Boland M. Green kiwifruit PJ, Rutherfurd SM. Dietary actinidin from kiwifruit (Actinidia modulates the colonic microbiota in growing pigs. Lett Appl deliciosa cv. Hayward) increases gastric digestion and the Microbiol. 2011;52:379-85. gastric emptying rate of several dietary proteins in growing rats. 5. Rosendale DI, Blatchford PA, Sims IM, Parkar SG, Carnachan J Nutr. 2014;144:440-6. SM, Hedderley D, Ansell J. Characterizing kiwifruit carbohydrate 25. Zespri®: Data on file. utilization in vitro and its consequences for human faecal 26. Rush EC, Patel M, Plank LD, Ferguson LR. Kiwifruit promotes microbiota. J Proteome Res. 2012;11:5863-75. laxation in the elderly. Asia Pac J Clin Nutr. 2002;11:164-8. 6. O’Hara AM, Shanahan F. The gut flora as a forgotten organ. 27. Chan AO, Leung G, Tong T, Wong NY. Increasing dietary fiber EMBO Reports. 2006;7:688-93. intake in terms of kiwifruit improves constipation in Chinese 7. Garcia-Lafuente A, Antolin M, Guarner F, Crespo E, Malagelada patients. World J Gastroenterol. 2007;13:4771-5. JR. Modulation of colonic barrier function by the composition of 28. Chang CC, Lin YT, Lu YT, Liu YS, Liu JF. Kiwifruit improves the commensal flora in the rat. Gut. 2001;48:503-7. bowel function in patients with irritable bowel syndrome with 8. Sims IM, Monro JA. Fiber: Composition, structures, and constipation. Asia Pac J Clin Nutr. 2010;19:451-7. functional properties. Adv Food Nutr Res. 2013;68:81-99. 29. Cunillera O, Almeda J, Mascort JJ, Basora J, Marzo-Castillejo M and 9. Redgwell RJ, Melton LD, Brasch DJ. Cell wall dissolution in the Catalan Kiwifruit Study Group. Improvement of functional ripening kiwifruit (actinidia deliciosa): Solubilization of the constipation with kiwifruit intake in a Mediterranean patient pectic polymers. Plant Physiol. 1992;98:71-81. population: An open, non-randomised pilot study. Rev Esp Nutr 10. Redgwell RJ, Fisher M, Kendal E, MacRae EA. Galactose loss and Hum Diet. 2015;19:58-67. fruit ripening: high-molecular-weight arabinogalactans in the 30. Zespri®: Data on file. pectic polysaccharides of fruit cell walls. Planta. 1997;203:174– 31. Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. A diet 81. low in fodmaps reduces symptoms of irritable bowel syndrome. 11. Marlett JA, Kajs TM, Fischer MH. An unfermented gel component Gastroenterology 2014;146:67-75 e65. of psyllium seed husk promotes laxation as a lubricant in 32. Ong D, Mitchell S, Barrett J, et al. Manipulation of dietary short humans. Am J Clin Nutr. 2000;72:784-9. chain carbohydrates alters the pattern of gas production 12. Montoya CA, Rutherfurd SM, Olson TD, Purba AS, Drummond and genesis of symptoms in irritable bowel syndrome. J LN, Boland MJ, Moughan PJ. Actinidin from kiwifruit (Actinidia Gastroenterol Hepatol 2010; 25: 1366-73. deliciosa cv. Hayward) increases the digestion and rate of 33. Barrett J, Gearry R, Muir J, et al. Dietary poorly absorbed, short- gastric emptying of meat proteins in the growing pig. Br J Nutr. chain carbohydrates increase delivery of water and fermentable 2014;111:957-67. substrates to the proximal colon. Aliment Pharmacol Ther 2010; 13. Kaur L, Rutherfurd SM, Moughan PJ, Drummond L, Boland 31: 874-82. MJ. Actinidin enhances gastric protein digestion as assessed 34. Marciani L, Cox E, Hoad C, et al. Postprandial changes in small using an in vitro gastric digestion model. J Agric Food Chem. bowel water content in healthy subjects and patients with 2010;58:5068-73. irritable bowel syndrome. Gastroenterology 2010; 138: 469-77. 14. Kaur L, Rutherfurd SM, Moughan PJ, Drummond L, Boland MJ. 35. Staudacher HM, Lomer MC, Anderson JL, et al. Fermentable Actinidin enhances protein digestion in the small intestine as carbohydrate restriction reduces luminal bifidobacteria and assessed using an in vitro digestion model. J Agric Food Chem. gastrointestinal symptoms in patients with irritable bowel 2010;58:5074-80. syndrome. J Nutr 2012; 142: 1510-8. 15. Drummond L, Gearry RB. Kiwifruit modulation of 36. Staudacher H, Whelan K, Irving P, Lomer M. Comparison gastrointestinal motility. Adv Food Nutr Res. 2013;68:219-32. of symptom response following advice for a diet low in 16. Parkar SG, Rosendale D, Paturi G, Herath TD, Stoklosinski fermentable carbohydrates (FODMAPs) versus standard dietary H, Phipps JE, Hedderley D, Ansell J. In vitro utilization of gold advice in patients with irritable bowel syndrome. J Hum Nutr and green kiwifruit oligosaccharides by human gut microbial Diet 2011; 24: 487-95. populations. Plant Foods Hum Nutr. 2012;67:200-7. 37. De Roest R, Dobbs B, Chapman B, et al. The low FODMAP diet 17. Bentley-Hewitt KL, Blatchford PA, Parkar SG, Ansell J, Pernthaner improves gastrointestinal symptoms in patients with irritable A. Digested and fermented green kiwifruit increases human bowel syndrome: A prospective study. Int J Clin Pract 2013; 67: beta-defensin 1 and 2 production in vitro. Plant Foods Hum 895-903. Nutr. 2012;67:208-14. 38. Biesiekierski J, Peters S, Newnham E, Rosella O, Muir J, Gibson 18. Blatchford P, Bentley-Hewitt KL, Stoklosinski H, McGhie T, P. No effects of gluten in patients with self-reported non- Gearry R, Gibson G, Ansell J. In vitro characterisation of the celiac gluten sensitivity following dietary reduction of low- fermentation profile and prebiotic capacity of gold-fleshed fermentable, poorly-absorbed, short-chain carbohydrates. kiwifruit. Benef Microbes. 2015:1-12. Gastroenterology 2013; 145: 320-8. 19. Molan AL, Kruger MC, and Drummond, L.N. : The ability of 39. Monash University (2015). The Monash University Low FODMAP kiwifruit to positively modulate markers of gastrointestinal Diet for Apple iOS (Version 1.5.1.) [Mobile application software]. health. Proceedings of the Nutrition Society of New Zealand Retrieved from https://itunes.apple.com/au/app/monash- 2007;32: 66-71. university-low-fodmap/id586149216?mt=8 20. Parkar SG, Redgate EL, Wibisono R, Luo X, Koh ETH, Schrӧder R. Gut health benefits of kiwifruit pectins: Comparison with commercial functional polysaccharides. J Funct Foods. 2010;2:210-8.

37 Nutrition Vitamin C and Healthand Health

Attributes Vitamin C and Health of Kiwifruit Vitamin C and Health

Vitamin C is an Essential Vitamin that Cannot Be Synthesised by the Human Body

Vitamin C, also known as ascorbic acid or ascorbate (Figure 1), is a water-soluble vitamin that is naturally present in some foods and available as a dietary supplement. While some animals can synthesise their own vitamin C from glucose, humans do not have this ability and therefore must obtain vitamin C through the diet1. The human body can store only a certain amount of vitamin C, so it must be ingested on a daily basis1. An adequate intake of vitamin C is required for the proper development and function of many parts of the body, and has been shown to limit the risk of developing chronic diseases such as heart disease and cancer1, 2.

Figure 1. Chemical structure of vitamin C (ascorbic acid or ascorbate)

O HO

O

HO H HO C H

CH2OH

41 Vitamin C Has an Important Role in Human Metabolic Processes

Vitamin C has important effects on the body, and contributes to:

• Normal function of the immune system Vitamin C plays an important role in immune function, and has been shown to have immunostimulant, anti-inflammatory, antiviral and antibacterial properties3,4.

• Energy metabolism Vitamin C is required for the synthesis of carnitine, a compound that plays a critical role in energy production, by transporting long-chain fatty acids into the cell so they can be oxidized (‘burned’) for fuel5.

• Normal psychological function, which helps to reduce tiredness and fatigue Vitamin C helps to activate a series of enzymes that improve metabolic energy levels and different neurochemicals in the brain, therefore taking vitamin C could reduce the sensation of fatigue and increase physical and mental energy6-8.

• Tissue formation and wound healing Vitamin C is required for the biosynthesis of collagen, an essential component of connective tissue which plays a vital role in wound healing9.

• Production of a range of enzymes Vitamin C is required as a cofactor (or “helper molecule” that assists in biochemical reactions) for a number of different enzymes which play important roles in the maintenance of normal metabolism and cellular responses to environmental stresses10-12.

• Protection of cellular DNA, proteins and lipids Vitamin C is a powerful antioxidant and can help reduce the damage to cells and tissues caused by the products of normal metabolism (see Breakout box 1)13. It has also been shown to regenerate other antioxidants within the body, including vitamin E14.

• Maintenance of the structure and function of the skeletal muscle Due to its role in creating collagen and protecting metabolically active cells from oxidative stress, vitamin C can help to protect muscle tissue against damage by free radicals15,16.

Breakout box 1: Antioxidants13, 17

Antioxidants are natural or man-made substances that may prevent or delay some types of cell damage. They do this by blocking some of the damage caused by free radicals, unstable molecules created every day during normal metabolism that damage DNA. The build-up of free radicals over time may contribute to the aging process and the development of health conditions such as cancer, heart disease, and arthritis. On-going research is examining the role of antioxidants in the prevention or delay of the development of certain cancers, cardiovascular disease, and other diseases in which oxidative stress plays a fundamental role.

42 How Much Vitamin C Do We Need?

The current US recommended dietary allowance (RDA, see Breakout box 2) for vitamin C, established by the Food and Nutrition Board/National Research Council in 1980 and reconfirmed in 1989, is 60 mg daily18, 19. However, more recent research suggests that the RDA for vitamin C should be increased.

Fruits and vegetables are generally regarded as the best available source of vitamin C. However, because ascorbic acid is water soluble and destroyed by heat, the vitamin C content of food may be reduced by prolonged storage and cooking20. Fortunately, most fruits and some vegetables can be consumed raw and consuming several varied servings of fruits and vegetables a day can provide more than the RDA of vitamin C.

Breakout box 2: Recommended Dietary Allowance (RDA)

The RDA is the average daily level of intake sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals20. The RDA for vitamin C, based on its known physiological and antioxidant functions in white blood cells, is set much higher than the amount required for protection from deficiency while ensuring that there is minimal excretion in the urine20.

However, since the last RDA review which recommends 60 mg of vitamin C daily, scientists have suggested a need for elevated vitamin C consumption. A 1996 study by Levine et al., which investigated vitamin C pharmacokinetics in seven healthy men, proposed that the RDA should be increased to 200 mg daily21. Based on these newer studies, the recommended level in the US was increased from 60 mg/day to 90 mg/day for men and from 45 mg/day to 75 mg/day for women in 2000. In Australasia, the RDA remains at 45 mg/day22.

43 One Zespri® Kiwifruit a Day Gives the Daily Requirement of Vitamin C

Zespri® kiwifruit is one of the best sources of vitamin C among fruit and vegetables (Figure 2). Zespri SunGold kiwifruit contains almost three times the amount of vitamin C found in oranges and strawberries, traditionally known as good sources of vitamin C23.

Figure 2. Graph comparing the vitamin C content of various fruits with Zespri® kiwifruit23

200

161.3 150

100 85.1 84.0 EU RDA 60.9 58.8 100% Vitamin C (mg/100 g) Vitamin 53.2 47.8 50 36.4 26.7 18.0 19.7 EU 8.7 14 9.7 8.1 10.2 4.6 4.0 4.3 RDA 0 15%

Pears Apples Grapes Melons Bananas Oranges PapayasMangoes LongansDurians Blueberries Pineapples Cranberries MandarinesStrawberries Zespri Green** WatermelonsPomegranates Zespri SunGold*

* USDA Nutrient Database 2015 (Release 28) ** New Zealand FOODfiles 2014 Version 01

Zespri® Kiwifruit is Very Effective at Increasing Plasma Levels of Vitamin C

Vitamin C status is typically assessed by measuring blood plasma vitamin C levels14, 24. This is because human tissues are not always accessible for evaluation, and since blood is the vehicle for vitamin C transport, plasma concentrations are a reasonable indicator of its concentration in the body.

A recent study in New Zealand showed that regular consumption of two gold kiwifruit significantly increased plasma levels of ascorbic acid (vitamin C) in men with a normal level of vitamin C15. This effect was even greater in those with previous low levels of vitamin C15.

This study determined a comparable relative bioavailability of kiwifruit-derived vitamin C and synthetic vitamin C in non-smoking males that received either a chewable tablet (200 mg vitamin C) or the equivalent dose from kiwifruit15.

44 Kiwifruit and Vitamin C-Related Health: EX VIVO What is the Evidence? STUDIES

Consumption of kiwifruit is associated with enhanced immune cell function

Vitamin C is thought to be essential for the function of neutrophils, cells of the immune system that defend against invading pathogens (see Breakout box 3). A recent study has demonstrated that supplementation with vitamin C-rich kiwifruit improves important neutrophil functions, which likely translates to enhanced immunity25.

Breakout box 3: Neutrophils and inflammation25

Neutrophils are the most common type of white blood cell and form an essential part of the innate immune system. They detect and migrate to sites of infection (a process known as chemotaxis) where they engulf and kill micro-organisms. This process, known as phagocytosis, requires oxygen and results in the secretion of chemically reactive molecules called reactive oxygen species (ROS). The release of ROS is also known as an ‘oxidative burst’.

Neutrophils in the Movement into tissues Phagocytosis and circulation (chemotaxis) destruction of bacteria

Bacteria

Oxidative burst

In this study, young men with low vitamin C status were fed two Zespri SunGold kiwifruit daily for a period of 4 weeks25. Plasma vitamin C levels increased to >70 μmol/L within one week of supplementation (Figure 3a) and a significant increase in neutrophil vitamin C status following four weeks of kiwifruit supplementation was seen (Figure 3b).

45 Figure 3 (a). Plasma vitamin C levels25

Week 4: Supplementation with 100 two kiwifruit/day

80 mol/L) 60

40

Plasma vitamin C ( µ 20

0 1 2 3 4 5 6 7 8 Weeks

Figure 3 (b). Neutrophil vitamin C status following 4 weeks of kiwifruit supplementation25

30 P=0.016 25

20

15

10

5 Neutrophil vitamin C (μmol/108 cells) Neutrophil 0 Baseline Post-intervention

In addition to increased plasma and neutrophil vitamin C status, a statistically significant 20% increase in neutrophil chemotaxis was observed post-intervention, demonstrating that vitamin C enhances the anti-microbial function of neutrophils (Figure 4a). Additionally, concentrations of the superoxide, a type of ROS (see Breakout box 3), increased, which likely translates into enhanced microbial killing capacity (Figure 4).

46 Figure 4. Neutrophil chemotaxis (a) and superoxide generation (b) at baseline and post-intervention25

a 3.5 b 12 * * 3.0 10 2.5 8 cells) 2.0 6 6 1.5 4 1.0 ( µ mol/min/10 (Increase in max. rate) in max. (Increase Neutrophil superoxide Neutrophil Neutrophil chemotaxis Neutrophil 0.5 2

0 0 Baseline Post-intervention Baseline Post-intervention

Chemotaxis Superoxide production

Data represent mean ± SEM (n=12 and 11) *p<0.05

Vitamin C is retained in parts IN VIVO of the body where it is most essential STUDIES

A study using a Gulo mouse model investigated the effectiveness of vitamin C uptake from a kiwifruit gel (Zespri Green and Gold kiwifruit) compared to a synthetic supplement over a period of 4 weeks26. Like humans, these animals are incapable of synthesising vitamin C, but can be healthy and grow normally when the vitamin is added to the diet. After 4 weeks, mice fed with the kiwifruit gel-supplemented diet had substantially higher tissue levels of vitamin C than those mice consuming an equivalent dose of vitamin C in the drinking water (Figure 5)26. Whilst the striking results suggested a differential uptake, this has not been observed in human studies. The observed differences are believed to be related to the different set and pattern of vitamin C transporters in the mice, which normally manufacture their own vitamin C and are therefore less well equipped to absorb dietary sources.

Importantly, the authors of this study also noted that a suboptimal intake of dietary vitamin C could lead to reductions in intracellular vitamin C, particularly in the liver and kidneys. Interestingly, the brain was found to be most resilient, with approximately 50% of vitamin C remaining after 1 week and close to 10% of the initial content being detectable after 4 weeks26. These results demonstrate that vitamin C is preferentially accumulated in brain tissue, indicating a vital role for vitamin C in the brain26. The study also showed that mice with suboptimal levels of vitamin C appeared to be healthy for a prolonged period before overt signs of poor health appeared, suggesting the suboptimal levels meant they were basically “unwell”.

47 Figure 5. Tissue vitamin C concentrations in mice fed kiwifruit gel with a known vitamin C content ( ) or synthetic vitamin C supplement in drinking water ( )26

Serum Brain 60 3

50

40 2 mol/L) mol/g) 30

20 1 Ascorbate ( µ Ascorbate ( µ 10

0 0 0 1 2 3 4 5 0 1 2 3 4 5

White blood cells Liver 6 1.0 5 cells)

7 0.8 4 mol/g) 0,6 mol/10 3 0.4 2 Ascorbate ( µ 1 0.2 Ascorbate ( µ

0 0.0 0 1 2 3 4 5 0 1 2 3 4 5

Heart Kidney 0.20 0.5

0.15 0.4 mol/g) mol/g) 0.3 0.10 0.2

Ascorbate ( µ 0.05 Ascorbate ( µ 0.1

0.00 0.0 0 1 2 3 4 5 0 1 2 3 4 5

Ascorbate intake (mg per day) Ascorbate intake (mg per day)

Each data point represents the mean (±SE) value for 3 to 12 animals. Reagent ascorbate (4.2 mg/d) was also delivered in a gel form to control for differences in absorption ( ).

48 Consumption of one kiwifruit per day is sufficient CLINICAL to achieve ‘healthy’ plasma levels of vitamin C STUDIES

To more accurately measure the contribution of kiwifruit (Zespri Gold kiwifruit) to dietary vitamin C intake, plasma vitamin C levels were measured in a group of 14 male students with low vitamin C status (average baseline plasma 38 mM)27. Participants were asked to consume half a kiwifruit per day for 4 weeks, followed by one kiwifruit per day for 6 weeks, two kiwifruit per day for 6 weeks and finally three kiwifruit per day for 4 weeks (Figure 6)27.

Figure 6. Study design27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Weeks

Lead-in 1/2 kiwifruit/d 1 kiwifruit/d 2 kiwifruit/d 3 kiwifruit/d Washout Baseline Phase I Phase II (intervention) Phase III

Lead-in phase of 4 weeks, intervention phase of 20 weeks and a washout phase of 4 weeks. * Fasting blood samples † 24h urine collection and total leucocyte preparations carried out when food and beverage diaries completed

The results showed that consuming kiwifruit had a strong effect on plasma vitamin C levels, with increases of around 25 mM (Figures 7a and b)27. The addition of as little as half a kiwifruit per day resulted in a significant increase in plasma vitamin C, however, one kiwifruit per day was required to reach what is considered healthy levels27. At two kiwifruit per day, plasma levels approached saturation with no further increase with three per day27. This was confirmed by increased urinary output of the vitamin at two kiwifruit per day (which coincided with plasma levels reaching around 60 mM; Figure 8)27.

These results confirm the pharmacokinetic data of Levine et al.21 (see Breakout box 2) and indicate that plasma vitamin C levels in humans saturate at an intake of about 200 mg/day27. This is equivalent to eating approximately two kiwifruit per day.

49 Figure 7. (a) Daily fruit and vegetable consumption and (b) vitamin C intake by the study participants27

a b 7 350

(8) 6 (8) 300 (9) (9) 5 (14) (8) 250 (9) (14) 4 200

3 150 (9)

100 2 (14) (8) (14) 1 C intake (mg/day) Vitamin 50 Fruit & Vegetable Servings/day Vegetable & Fruit

0 0 0 0.5 1 2 3 WO 0 0.5 1 2 3 WO Number of kiwifruit/day Number of kiwifruit/day

Total fruit and vegetable intake or vitamin C intake Total minus kiwifruit intervention

Data are means with standard errors represented by vertical bars. The number of participants are indicated in parentheses. * Mean value was significantly different from that at baseline (P<0.05; one-way repeated-measures ANOVA with the Fisher least significant deviation pairwise multiple comparison procedure). WO, washout.

Figure 8. Correlation of plasma vitamin C with urinary excretion of vitamin C27

Increased urinary output of vitamin C with plasma levels of 60 mM 400

300

200

100 Urinary vitamin C (mg/24 h) Urinary

0 0 15 30 45 60 75 90 Plasma vitamin C (µmol/l)

Correlation of plasma vitamin C with urinary excretion of vitamin C. Data points (n 62) were of obtained from partici- pants at each stage of the study (baseline, 0.5 KF/d, 1 KF/d, 2 KF/d, 3 KF/d, WO).

50 Kiwifruit effectively increases vitamin C levels in blood plasma and skeletal muscle

A study investigating the bioavailability of vitamin C to human skeletal muscle found that muscle is highly responsive to vitamin C intake (and hence plasma concentrations), and is likely to be prone to depletion with inadequate dietary intake15. In this study, 36 men were given either half a kiwifruit or two kiwifruits (Zespri Gold kiwifruit) per day for 6 weeks. Baseline mean muscle tissue vitamin C concentrations were ∼16 nmol/g tissue, with a range from 1.0 to 43.2 nmol/g tissue.

After 6 weeks of kiwifruit consumption, there was a ∼3.5-fold increase in mean muscle tissue vitamin C concentrations to 53 and 61 nmol/g tissue in the low- and high-dose groups, respectively15. Authors also measured vitamin C concentrations of mononuclear cells and neutrophils, which showed a significantly smaller relative uptake of vitamin C compared with muscle tissue uptake (Figure 9)15. There was no difference in muscle tissue ascorbate concentrations between the two groups, which suggested that muscle tissue vitamin C concentrations were saturated with half a kiwifruit per day15. Authors of this study suggest that daily vitamin C intake that provides plasma vitamin C concentrations ≥50 μmol/L should be consumed to maintain an optimal skeletal muscle vitamin C status15.

Figure 9. Mean ± SEM relative increases in vitamin C concentrations in peripheral blood mononuclear cells, neutrophils and skeletal muscle tissue15

400

300

200 Increase in ascorbate (% of baseline) Increase 100 Mononuclear cells Neutrophils Muscle tissue

Supplementation with 0.5 kiwifruit/d (n = 18; green bars) or 2 kiwifruit/d (n = 18; yellow bars) *p<0.01; **p<0.001

51 Kiwifruit supplementation improves overall mood

A recent study in young men has shown that eating two kiwifruit (Zespri Gold kiwifruit) per day can improve a person’s overall mood6. In this study, 35 young men were supplemented with either half or two kiwifruit per day for 6 weeks. No effect on overall mood was observed in the group who ate half a kiwifruit per day; however, in the group that ate two kiwifruits per day, decreased total mood disturbance and depression trends were seen6. Further analysis of a subgroup of participants with higher than average mood disturbance indicated a significant decrease in fatigue, a concomitant increase in vigour, and a trend towards a decrease in depression following supplementation with two kiwifruit per day, but not half a kiwifruit per day (Figure 10)6.

The authors state that these improvements are likely related to the optimisation of vitamin C with the dose provided by two kiwifruit6. These results are consistent with other studies which have reported reductions in depression, fatigue and mood disturbance with vitamin C supplementation6.

Figure 10. Effect of two kiwifruit/day intervention on individual mood scores and total mood disturbance (TMD) score in the high-TMD subgroup (n=8)6

50

40 *

30

*

Mood score 20

* 10

0

TMD Anger Vigour Tension Fatigue Depression Confusion

Baseline Intervention

Data are means, with standard errors represented by vertical bars. *Mean value was significantly different from that at baseline (p<0.05; two-tailed paired T test)

52 Table 1. Summary of key outcomes from human studies investigating vitamin C from kiwifruit6, 15, 25-27

0.5 kiwifruit/day 2 kiwifruit/day

Plasma vitamin C + ++

Seminal fluid ­- +

Mononuclear cells + +

Neutrophils ++ ++

Muscle +++ +++

Mood score - ++

Kiwifruit consumption increases protective cellular defence

A human clinical trial found that the intake of antioxidant-rich foods could affect groups of genes associated with cellular stress defence when participants added kiwifruit to their diet28. In this study, 102 healthy male smokers were randomised to either a diet rich in various antioxidant-rich foods, a kiwifruit diet (three kiwifruits/day added to their regular diet) or a control group28.

Groups of genes involved in regulation of cellular stress defence, such as DNA repair, apoptosis and hypoxia (preventing cellular oxygen deprivation), were significantly up-regulated in participants who ate three kiwifruits per day or an antioxidant-rich diet28. Antioxidants in blood plasma, such as polyphenols and carotenoids, also increased in both groups28.

The authors of the study suggest that antioxidants found in fruits and vegetables control ROS (Reactive Oxygen Species) levels while also regulating immune defence systems (Figure 11). Antioxidant intake could therefore help prevent oxidative stress-related diseases and premature aging28.

53 Figure 11. Hypothetical model suggesting how antioxidants in fruits and vegetables influence protective cellular defence systems28

Fruits/berries/vegetables Endogenous sources of ROS Exogenous sources of ROS Endogenous sources of ROS Exogenous sources of ROS

ROS ROS ROS too low optimal level too high

Damage to DNA Cell signalling membranes, proteins etc

Modulation of gene expression

Increased cellular Damaged cells stress defence

Healthy cells Ageing/diseases/cell death

54 Kiwifruit consumption reduces selected upper respiratory tract infection symptoms

The common cold or influenza (flu) viruses, some of the most common causes of sickness in humans, cause symptoms of upper respiratory tract infection (URTI) such as sore throat and head congestion29. There is no specific therapy to prevent or treat the common cold, and flu vaccination is only modestly effective in older adults29. Since inadequate nutrition can contribute to increased risk and severity of URTI in the elderly, a 2012 study investigated whether kiwifruit (Zespri Gold kiwifruit), a food rich in vitamins C and E, folate, polyphenols and carotenoids, could reduce URTI symptoms29.

In this study, 32 elderly people (≥65 years) consumed the equivalent of four kiwifruit or two bananas daily for 4 weeks29. While kiwifruit did not significantly reduce the overall incidence of URTI compared with banana, the severity and duration of head congestion, and the duration of sore throat were reduced29. There was also a positive and significant influence on a number of plasma antioxidants, including vitamins C, vitamin E and lutein/zeaxanthin, and cellular damage from oxidative stress was significantly reduced. Authors conclude that eating kiwifruit may provide an important contribution to lessening the burden of respiratory infection in older people29.

Upcoming Research

The antioxidant properties of vitamin C and its role in collagen synthesis make it a vital molecule for skin health1. Vitamin C in the skin is normally transported from the bloodstream and is found at high levels in both the dermis and epidermis of human skin30. Levels of vitamin C decline with age and excessive exposures to UV light or pollutants such as cigarette smoke31,32, and therefore supplementation to increase vitamin C levels in the skin is common.

Numerous studies have demonstrated that oral supplementation with vitamin C effectively increases vitamin C levels in the skin33, 34, and recent evidence shows that combining vitamin C and vitamin E supplementation is more effective in preventing UV damage than either vitamin alone35, 36. Since Zespri® kiwifruit contains both vitamin C and vitamin E in relatively high levels, investigations into the role of kiwifruit supplementation in improving skin health and combatting signs of ageing are currently in planning stages.

55 Conclusions

• Vitamin C is an essential vitamin that cannot be synthesised by the human body, and therefore must be obtained through the diet.

• An adequate intake of vitamin C is required for the activation of numerous enzymatic reactions, various metabolic processes and the supply of antioxidants which protect against oxidative stress; deficiencies in vitamin C disrupt pathways known to cause chronic diseases, such as heart disease and cancer.

• Vitamin C plays an important role in both innate and adaptive immune system function, and is found in high concentrations in immune cells.

• Vitamin C levels in tissues are rapidly depleted, and since the human body can store only a certain amount of vitamin C, it must be ingested on a daily basis.

• Kiwifruit is a rich source of vitamin C and has been shown to be a significantly better at replenishing depleted vitamin C tissue levels compared with vitamin C supplements37; just one Zespri kiwifruit a day contains the daily requirement of vitamin C.

56 References

1. World Health Organization. Vitamin and mineral requirements 23. USDA. USDA national nutrient database for standard reference in human nutrition : report of a joint FAO/WHO expert (Release 28). 2015. consultation, Bangkok, Thailand, 21–30 September 1998. 2004. 24. Bates CJ. Bioavailability of vitamin C. Eur J Clin Nutr. 2. Vissers MC, Carr AC, Pullar JM, Bozonet SM. The bioavailability 1997;51(Suppl 1):S28-33. of vitamin C from kiwifruit. Adv Food Nutr Res. 2013;68:125-47. 25. Bozonet SM, Carr AC, Pullar JM, Vissers MC. Enhanced 3. Bergsten P, Amitai G, Kehrl J, Dhariwal KR, Klein HG, Levine M. human neutrophil vitamin C status, chemotaxis and oxidant Millimolar concentrations of ascorbic acid in purified human generation following dietary supplementation with vitamin mononuclear leukocytes. Depletion and reaccumulation. J Biol C-rich SunGold kiwifruit. Nutrients. 2015;7:2574-88. Chem. 1990;265:2584-7. 26. Vissers MC, Bozonet SM, Pearson JF, Braithwaite LJ. Dietary 4. Washko PW, Wang Y, Levine M. Ascorbic acid recycling in human ascorbate intake affects steady state tissue concentrations in neutrophils. J Biol Chem. J Biol Chem. 1993;268:15531-5. vitamin C-deficient mice: tissue deficiency after suboptimal 5. Huskisson E, Maggini S, Ruf M. The role of vitamins and minerals intake and superior bioavailability from a food source (kiwifruit). in energy metabolism an wellbeing. J Int Med Res. 2007;35:277- Am J Clin Nutr. 2011;93:292-301. 89. 27. Carr AC, Pullar JM, Moran S, Vissers MC. Bioavailability of 6. Carr AC, Bozonet SM, Pullar JM, Vissers MC. Mood improvement vitamin C from kiwifruit in non-smoking males: determination in young adult males following supplementation with gold of ‘healthy’ and ‘optimal’ intakes. J Nutr Sci. 2012;1:e14. kiwifruit, a high-vitamin C food. J Nutr Sci. 2013;2:e24. 28. Bøhn SK, Myhrstad MC, Thoresen M, Holden M, Karlsen A, 7. Rebouche CJ. Ascorbic acid and carnitine biosynthesis. Am J Clin Tunheim SH, Erlund I, Svendsen M, Seljeflot I, Moskaug JO, Nutr. 1991;54(6 Suppl):S1147-S52. Duttaroy AK, Laake P, Arnesen H, Tonstad S, Collins A, Drevon CA, Blomhoff R. Blood cell gene expression associated with 8. Kinsman RA, Hood J. Some behavioral effects of ascorbic acid cellular stress defense is modulated by antioxidant-rich food deficiency. Am J Clin Nutr. 1971;24:455-64. in a randomised controlled clinical trial of male smokers. BMC 9. Moores J. Vitamin C: a wound healing perspective. Br J Med. 2010;8:54. Community Nurs. 2013(6 Suppl):S8-11. 29. Hunter DC, Skinner MA, Wolber FM, Booth CL, Loh JM, Wohlers 10. Englard S, Seifter S. The biochemical functions of ascorbic acid. M, Stevenson LM, Kruger MC. Consumption of gold kiwifruit Annu Rev Nutr. 1986;6:365-406. reduces severity and duration of selected upper respiratory 11. Padayatty SJ, Levine M. Vitamin C: the known, the unknown, tract infection symptoms and increases plasma vitamin C and Goldilocks. Oral Dis. 2016 [Epub ahead of print] concentration in healthy older adults. Br J Nutr. 2012;108:1235- 45. 12. Rumsey SC, Levine M. Absorption, transport, and disposition of ascorbic acid in humans. J Nutr Biochem 1998;9:116-130. 30. Shindo Y, Witt E, Han D, Epstein W, Packer L. Enzymic and non- enzymic antioxidants in epidermis and dermis of human skin. 13. Ginter E, Simko V, Panakova V. Antioxidants in health and J Invest Dermatol. 1994;102:122-4. disease. Bratisl Lek Listy. 2014;115:603-6. 31. Podda M, Traber MG, Weber C, Yan LJ, Packer L. UV-irradiation 14. Jacob RA, Sotoudeh G. Vitamin C function and status in chronic depletes antioxidants and causes oxidative damage in a model disease. Nutr Clin Care 2002;5:66-74. of human skin. Free Radic Biol Med. 1998;24:55-65. 15. Carr AC, Bozonet SM, Pullar JM, Simcock JW, Vissers MC. Human 32. Rhie G, Shin MH, Seo JY, Choi WW, Cho KH, Kim KH, Park KC, skeletal muscle ascorbate is highly responsive to changes in Eun HC, Chung JH. Aging- and photoaging-dependent changes vitamin C intake and plasma concentrations. Am J Clin Nutr. of enzymic and nonenzymic antioxidants in the epidermis and 2013;97:800-7. dermis of human skin in vivo. J Invest Dermatol. 2001;117:1212- 16. Frei B, England L, Ames BN. Ascorbate is an outstanding 7. antioxidant in human blood plasma. Proc Natl Acad Sci USA. 33. Fuchs J, Kern H. Modulation of UV-light-induced skin 1989;86:6377-81. inflammation by D-alpha-tocopherol and L-ascorbic acid: a 17. National Institutes of Health. Antioxidants and Health: An clinical study using solar simulated radiation. Free Radic Biol Introduction. 2015; Available from: https://nccih.nih.gov/health/ Med. 1998;25:1006-12. antioxidants/introduction.htm [cited 05 January 2015] 34. McArdle F, Rhodes LE, Parslew R, Jack CI, Friedmann PS, Jackson 18. FNB/NRC. Recommended Dietary Allowances. Tenth Revised MJ. UVR-induced oxidative stress in human skin in vivo: Edition; Food and Nutrition Board. 1989: Washington, DC. effects of oral vitamin C supplementation. Free Radic Biol Med. 19. FNB/NRC. Recommended Dietary Allowances. Ninth Revised 2002;33:1355-62. Edition; Food and Nutrition Board. 1980: Washington, DC. 35. Eberlein-König B, Placzek M, Przybilla B. Protective effect against 20. Institute of Medicine. Dietary Reference Intakes for Vitamin sunburn of combined systemic ascorbic acid (vitamin C) and C, Vitamin E, Selenium, and Carotenoidsexternal link d-alpha-tocopherol (vitamin E). J Am Acad Dermatol. 1998;38:45- disclaimer. 2000: Washington, DC. 8. 21. Levine M, Conry-Cantilena C, Wang Y, Welch RW, Washko PW, 36. Placzek M, Gaube S, Kerkmann U, Gilbertz KP, Herzinger T, Haen Dhariwal KR, Park JB, Lazarev A, Graumlich JF, King J, Cantilena E, Przybilla B. Ultraviolet B-induced DNA damage in human LR. Vitamin C pharmacokinetics in healthy volunteers: evidence epidermis is modified by the antioxidants ascorbic acid and for a recommended dietary allowance. Proc Natl Acad Sci USA. D-alpha-tocopherol. J Invest Dermatol. 2005;124:304-7. 1996;93:3704-9. 37. Stonehouse W, Gammon CS, Beck KL, Conlon CA, von Hurst 22. Boland M, Moughan PJ. Advances in Food And Nutrition PR, Kruger R. Kiwifruit: our daily prescription for health. Can J Research. Nutritional Benefits of Kiwifruit. 2013, Waltham, MA: Physiol Pharmacol. 2013;91:442-7. Elsevier Inc.

57 Nutrition Metabolic and HealthHealth Attributes of Kiwifruit Metabolic Health Metabolic Health

Kiwifruit Has a Low Glycaemic Index

The glycaemic index (GI) indicates the amount of glucose that is released during digestion from carbohydrates into the blood system within about two hours of a meal. High GI foods are rapidly digested and absorbed, and result in rapid, marked rise in plasma glucose levels, whereas the same amount of carbohydrate in low GI foods are more slowly digested and absorbed, resulting in a gradual rise in plasma glucose response and insulin levels1. Foods are classified as either:

• High GI (GI >70) • Medium GI (GI 55–70) • Low GI (GI <55)

Approximately 80% of the dry weight of kiwifruit consists of available carbohydrate, including glucose, fructose and sucrose at a ratio of about 2:2:1 (Figure 1)2. Of these sugars, glucose has a GI of 100% (reference value), fructose 19% and sucrose 68%2. The GI of kiwifruit reflects the proportion of sugars in the fruit, and any other factors that might reduce the rate at which the sugars are absorbed. Zespri Green kiwifruit has a GI of 39 and Zespri SunGold kiwifruit has a GI of 383. This puts kiwifruit in the GI category of ‘low’ (GI <55) (Figure 2).

Figure 1. Types of carbohydrates in kiwifruit2

20%

40%

40%

Glucose Fructose Sucrose

61 Figure 2. Relative glycaemic impact and GI of kiwifruit compared to other common foods2

GI: Low Medium High Kiwifruit (100 g) Potato mash Orange (120 g) Corn flakes Apple, raw (120 g) Bread Baked beans (150 g) Porridge (Oat) Bread (30 g) Banana Banana (120 g) Baked beans Oat porridge (250 g) Kiwifruit Potato mash (150 g) Spaghetti Corn flakes (30 g) Rice, white Rice, white (150 g) Orange Spaghetti (180 g) Apple, raw 0 5 10 15 20 0 10 20 30 40 50 60 70 80 Glycaemic impact (g glucose equivts./serving) Glycaemic index (%)

Kiwifruit Modulates Carbohydrate Digestion and Absorption

The remaining 20% of the dry weight of kiwifruit consists of protein (10%) and primary cell walls or fibre (10%)2. The cell wall component of kiwifruit is undigested in the stomach and small intestine, and therefore increases in relative concentration in the gut lumen2. During digestion, the fibre in kiwifruit swells to four times its original volume, which reduces the rate of glucose diffusion by about 40% and profoundly reduces digesta mixing, the process which enables the transfer of sugars from the intestinal lumen to the gut wall2. This causes a delay in carbohydrate digestion and absorption and may explain why the measured GI of whole kiwifruit (GI = 39) is much lower than would be calculated from the GI of the sugars alone (GI = 60).

The Glycaemic Response Per Kiwifruit is Low

The glycaemic response to a fruit depends not only on GI, but also on the amount of carbohydrate consumed in the fruit. As kiwifruit contains only about 12% available carbohydrate, and has a low GI, a 100 g kiwifruit is equivalent to about 5 g (1 teaspoon) of glucose in its glycaemic effect. The impact kiwifruit produces on plasma glucose levels is low enough for the fruit to be suitable in managing diets for people with a reduced tolerance to glucose, and suggests that kiwifruit may be beneficial in protecting against disorders related to absorption rate, such as the postprandial blood glucose excursion2.

62 Kiwifruit Can Help Manage Blood Sugar Levels in People With Diabetes

Diabetes mellitus is an alteration of the body’s tolerance to glucose, and has various causes4. About 382 million people in the world suffer from diabetes (between 5% and 6% of the population); in addition, there is a significant proportion of the population who, although not meeting all the criteria for diabetes, have challenges around managing their blood sugar levels5.

Diabetes leads to poor absorption of glucose from the blood by the body’s tissues, so that levels may build up in the blood. High blood glucose concentrations may lead to multiple complications4. Patients with diabetes require an adequately distributed intake of carbohydrates consumed in moderate quantity to prevent hyperglycaemic episodes, and carbohydrates with the lowest GI are the most appropriate4. With a low GI of 38–39, combined with a modest content of carbohydrate, and a fibre component that reduces the rate of absorption, kiwifruit is an excellent option for people with diabetes trying to manage their blood sugar levels.

Kiwifruit Affects Gut Microbiota

There is growing evidence that consumption of kiwifruit beneficially modulates the colonic microbiota (more information can be found in the Digestive Health section of this Scientific Pack)6-14. These colonic microbiota have recently been identified as a new potential factor in obesity-related disorders, including type 2 diabetes15. Growing evidence in clinical studies suggests that the colonic microbiota are altered in obese people, and it has been proposed that these alterations may lead to chronic low-level inflammation, insulin resistance and onset of type 2 diabetes16.

Kiwifruit and Metabolic Health: IN VITRO In Vitro and In Vivo Studies STUDIES

Kiwifruit reduces the rate of glucose diffusion

An in vitro study investigating the physicochemical properties of green and gold kiwifruit found that the undigested soluble and insoluble fibre in the kiwifruit cell walls was able to reduce the rate of processes involved in the glycaemic response17. In this study, kiwifruit flesh was digested under gastric and gastroileal conditions in vitro. The digested kiwifruit pulp of both green and gold varieties, which contained soluble and insoluble undigested polymer fractions, was found to swell to four times the volume of the original fruit and interact with other foods (Figure 3). This decreased the rate of glucose diffusion by over 40% and the rate of mixing by over 40%. Furthermore, in the presence of soluble fibre, the physical interaction of the cell wall remnants and long hydrocolloid molecules was found to increase viscosity and further decreased mixing. The authors concluded that the additive effects of decreased mixing and decreased diffusion are likely to reduce the glycaemic response, and may explain why the GI of the sugars consumed in kiwifruit is so much less than the GI of the same sugars consumed alone.

63 Figure 3. Volume of kiwifruit pulp before and after digestion

5 4.5 4 3.5 3 2.5 2 1.5

Volume of original fruit (ml) Volume 1 0.5 0 Before After digestion digestion

Green kiwifruit Gold kiwifruit

Figure adapted from Monro et al.2

Swollen volume of digestion-resistant remnants of kiwifruit from green and gold kiwifruit relative to the volume of the pulp before digestion. The digestion-resistant remnants had been allowed to settle overnight in a measuring cylinder.

Kiwifruit slows intestinal processes

In a series of in vitro studies, Monro et al.18 found that when kiwifruit flesh had been digested in vitro, the non-digested dietary fibre remnants would surround and extensively interact with other foods in the limited volume of the gut. These non-digested dietary fibre remnants of pre-digested kiwifruit flesh substantially retarded digestion, sugar diffusion and mixing of intestinal contents, all of them processes important to the glycaemic response.

64 Kiwifruit reduces the glycaemic impact of high CLINICAL carbohydrate foods and enhances nutrient absorption STUDIES

In a human intervention study conducted by Monro et al.18, the glycaemic impact of kiwifruit was found to be relatively low, with 100 g of kiwifruit exerting approximately the same effect on blood sugar levels as only 6 g of glucose. The authors conclude that this low in vivo glycaemic impact could be partly attributed to the carbohydrate in kiwifruit being fruit sugars, and partly to the non-digested kiwifruit remnants reducing the rate of intestinal processes such as digestion, sugar diffusion and mixing of intestinal contents18.

Researchers also found that partially substituting high glycaemic foods – such as those based on cereal starch – with kiwifruit improved uptake of nutrients, including vitamin C, and reduced the glycaemic response18. Interestingly, this glycaemic benefit was greatest when kiwifruit were consumed approximately 30 minutes before consumption of a cereal meal, substantially lowering both the amplitude of the response (the “spike”) compared with consuming the two foods together, while inducing a lower total response (area under the curve) compared with an equal carbohydrate amount of the non-substituted food. Authors conclude that partial substitution of starch-based staples, such as cereals, potatoes and rice, with kiwifruit is an effective dietary strategy to simultaneously reduce exposure to glycaemia while increasing the amount of nutrients consumed2.

Upcoming Research

A cross-sectional pilot study is currently underway to investigate the relationships between gut microbiota composition and diet in people with metabolic disorders19. The objectives of the study are to:

• Define gut microbiota composition associated with normal glucose tolerance, pre- diabetes and type 2 diabetes. • Identify dietary associations with gut microbiota composition with particular emphasis on fruit and vegetable intake.

Additionally, researchers plan to investigate the feasibility of an intervention study with kiwi- fruit to favourably alter gut microbiota composition, and therefore impact glucose tolerance.

65 Conclusions

• Zespri Green and Zespri SunGold kiwifruit have a low glycaemic index of 39 and 38, respectively, and deliver a modest amount of carbohydrate per fruit, resulting in a moderate rise in plasma glucose response and insulin levels.

• The fibre in kiwifruit increases in volume in the small intestine where it reduces digesta mixing, causing a delay in carbohydrate digestion and absorption, resulting in a low glycaemic potency (6.6 GGE/100 g).

− These properties make kiwifruit an excellent option for people with diabetes, and assist with management of blood sugar levels by carbohydrate exchange.

• Consumption of kiwifruit beneficially modulates colonic microbiota, which have been shown to be linked to chronic low-level inflammation, insulin resistance and onset of type 2 diabetes in obese people.

• Partial substitution of starch-based staple foods with kiwifruit is an effective dietary strategy to simultaneously improve glucose homeostasis and intake of some nutrients.

− Consuming a kiwifruit with breakfast could therefore be an effective and healthy way to reduce the glycaemic effect of high carbohydrate breakfast cereals, such as cornflakes.

66 References

1. Brand-Miller JC, Stockmann K, Atkinson F, Petocz P, Denyer G. 11. Ansell J, Parkar S, Paturi G, Rosendale D, Blatchford P. Modification Glycemic index, postprandial glycemia, and the shape of the of the colonic microbiota. Adv Food Nutr Res. 2013;68:205-17. curve in healthy subjects: Analysis of a database of more than 12. Carnachan SM, Bootten TJ, Mishra S, Monro JA, Sims IM. Effects 1,000 foods. Am J Clin Nutr. 2009;89:97-105. of simulated digestion in vitro on cell wall polysaccharides from 2. Monro JA. Kiwifruit, carbohydrate availability, and the glycemic kiwifruit (Actinidia spp.). Food Chemistry. 2013;133:132-9. response. Adv Food Nutr Res. 2013;68:257-71. 13. Rosendale DI, Blatchford PA, Sims IM, Parkar SG, Carnachan 3. Boland M, Moughan PJ. Advances in food and nutrition research. SM, Hedderley D, Ansell J. Characterizing kiwifruit carbohydrate Nutritional benefits of kiwifruit. Waltham, MA, Elsevier Inc, utilization in vitro and its consequences for human faecal 2013. microbiota. J Proteome Res. 2012;11:5863-75. 4. Piero MN, Nzaro GM, Njagi JM. Diabetes mellitus – a devastating 14. Blatchford P. Kiwifruit-driven microbiota, metabolites and metabolic disorder. Asian Journal of Biomedical and implications for human health. Abstract presented at: 1st Pharmaceutical Sciences 2014;04:1-7. International Symposium on Kiwifruit and Health; 2016 Apr 12- 5. International Diabetes Federation (IDF). IDF Diabetes Atlas, 6th 14; Tauranga, New Zealand. edition. Brussels, Belgium: 2013. 15. Egshatyan L, Kashtanova D, Popenko A, Tkacheva O, Tyakht A, 6. Parkar SG, Rosendale D, Paturi G, Herath TD, Stoklosinski Alexeev D, Karamnova N, Kostryukova E, Babenko V, Vakhitova H, Phipps JE, Hedderley D, Ansell J. In vitro utilization of gold M, Boytsov S. Gut microbiota and diet in patients with different and green kiwifruit oligosaccharides by human gut microbial glucose tolerance. Endocrine Connections. 2016;5:1-9. populations. Plant Foods Hum Nutr. 2012;67:200-7. 16. Zhang Y, Zhang H. Microbiota associated with type 2 diabetes 7. Bentley-Hewitt KL, Blatchford PA, Parkar SG, Ansell J, Pernthaner and its related complications. Food Science and Human A. Digested and fermented green kiwifruit increases human Wellness. 2013;2:167–72. beta-defensin 1 and 2 production in vitro. Plant Foods Hum 17. Mishra S, Monro J. Kiwifruit remnants from digestion in vitro Nutr. 2012;67:208-14. have functional attributes of potential importance to health. 8. Blatchford P, Bentley-Hewitt KL, Stoklosinski H, McGhie T, Food Chem. 2012;135:2188-94. Gearry R, Gibson G, Ansell J. In vitro characterisation of the 18. Monro J. Kiwifruit – a double agent for glycaemic control fermentation profile and prebiotic capacity of gold-fleshed and nutrient enhancement. Abstract presentation at: 1st kiwifruit. Benef Microbes. 2015:1-12. International Symposium on Kiwifruit and Health; 2016 Apr 12- 9. Molan AL, Kruger MC, Drummond LN. The ability of kiwifruit 14; Tauranga, New Zealand. to positively modulate markers of gastrointestinal health. 19. Wilson R. Diet, microbiota and metabolic health. Abstract Proceedings of the Nutrition Society of New Zealand. 2007;32:66- presentation at: 1st International Symposium on Kiwifruit and 71. Health; 2016 Apr 12-14; Tauranga, New Zealand. 10. Parkar SG, Redgate EL, Wibisono R, Luo X, Koh ETH, Schrӧder R. Gut health benefits of kiwifruit pectins: Comparison with commercial functional polysaccharides. Journal of Functional Foods. 2010;2:210-18.

67 Contact Details of Zespri® Spokespeople

Dr Juliet Ansell Dr Véronique Parmentier DPhil (Oxon): BSc, PhD: Innovation Leader Health Global Health Marketing & Nutrition at Zespri Manager at Zespri International Ltd International Ltd

Email: Email: [email protected] [email protected] Phone: +64 7 572 7798 Phone: +32 3 201 08 44

68 July 2016