Chapter 2
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Evaluating Health Benefits of Various Fruits Talwinder S. Kahlon* U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA 94710 *
[email protected] Fruits are an essential part of our daily diets. Most fruits are naturally low in fat, sodium, and calories. Fruits are important sources of many nutrients, including potassium, dietary fiber, vitamin C and folic, acid and they do not contain cholesterol. Some fruits have laxative effect, and prevent urinary tract infections or kidney stone formation. Phytonutrients in fruits have been shown to stimulate natural detoxifying enzymes in the body and lower the risk of atherosclerosis and cancer. Fruit consumption in US is less than half of the daily recommended level. Comprehensive national efforts are needed to increase fruit consumption for school children, adolescents and adults. Stock up fruits and never be fruitless! Bag some fruit for your morning commute. Buy fresh fruits in season when they taste best and cost less. The recommended consumption of fruits is 1 cup/1000 Calories or 2-2.5 cups (400-500g) per day. Fruit consumption needs to be doubled and it would improve nutrition and lower the risk of premature degenerative diseases.
Consumption of fruits as a significant portion of our daily diets has been associated with a lower risk of coronary heart disease and cancer (1–3). The USDA Food and Nutrition Information Center (2005) Food Guide Pyramid -Steps to a Healthier You (4) recommends daily active life, intake of low fat food products and consumption of vegetables and fruits. Food guide recommends consuming 1 cup/1000 calories or 2-2.5 cups (400-500g) of fruits every day. Most fruits are naturally low in fat, sodium, and calories. Fruits are important sources of many nutrients, including potassium, dietary fiber, vitamin C, folic acid and they © 2010 American Chemical Society Qian and Rimando; Flavor and Health Benefits of Small Fruits ACS Symposium Series; American Chemical Society: Washington, DC, 2010.
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do not contain cholesterol. Some of the fruits listed by the USDA food pyramid include apples, apricots, avocado, bananas, blueberries, cantaloupe, cherries, grapefruit, guava, grapes, honeydew, kiwi fruit, lemons, limes, loquat, leeches, mangoes, nectarines, oranges, papaya, peaches, pears, pineapple, plums, prunes, raisins, raspberries, strawberries, tangerines and watermelon. It also includes fruit cocktail and 100% fruit juice. Phytonutrients in these fruits have been shown to stimulate natural detoxifying enzymes in the body and lower the risk of atherosclerosis and cancer (5). Prevention of urinary tract infection and kidney stone formation with cranberry juice has been reported (6, 7). A laxative effect of prunes is believed to be due to its sorbitol, neochlorogenic and chlorogenic acids (8). Toxic metabolites in the gut and secondary bile acids increase the risk of colorectal cancer (9). Fruits are high in health promoting phytonutrients; blueberries, plums, prunes, strawberries, cranberries and cherries are rich in antioxidants, hydroxycinnamic acids, flavonoids (anthocyanins, flavonols, and proanthocyanidins), while apples contain polyphenols and catechins (10, 11).
Evaluating in Vitro Bile Acid Binding as Potential Health Benefits of Various Fruits In vitro bile acid binding without the use of labeled isotopes is an economical method for screening various foods and food fractions to evaluate their healthful potential before initiating time and cost intensive animal and human studies. Bile acids are acidic steroids synthesized in the liver from cholesterol. After conjugation with glycine or taurine, they are secreted into the duodenum. Bile acids are actively reabsorbed by the terminal ileum and undergo an enterohepatic circulation (12). The bile acids are needed for the absorption of dietary fat from the GI tract. The dietary fat is metabolized to acetate. Acetate is the principal precursor of cholesterol synthesis in the body. Binding of bile acids and increasing fecal excretion has been hypothesized as a possible mechanism for lowering cholesterol by dietary fiber (13–15). By binding bile acids, food fractions prevent their reabsorption and stimulate plasma and liver cholesterol conversion to additional bile acids (16–18). Toxic metabolites in the gut and secondary bile acids increase the risk of colorectal cancer (9). The healthful, cholesterol-lowering (atherosclerosis amelioration, detoxification of harmful carcinogenic metabolites) potential of food fractions could be predicted by evaluating their in vitro bile acid binding, based on positive correlations found between in vitro and in vivo studies showing that cholestyramine (bile acid binding, cholesterol lowering drug) binds bile acids and cellulose does not (19–22). In vitro bile acid binding procedure in described in Figure 1. Composition of various fruits tested for in vitro bile acid binding studies is given in Table I (23, 24). On dry matter basis the fruits tested ranged in values for carbohydrates (82-96%), total dietary fiber (5-36%), sugar (31-87%), polysaccharides (5-90%), protein 2-10%, fat (1-4%) and minerals (1-6%).
14 Qian and Rimando; Flavor and Health Benefits of Small Fruits ACS Symposium Series; American Chemical Society: Washington, DC, 2010.
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Figure 1. Diagram of the Bile Acid Binding Procedure (*0.1M phosphate buffer, pH 6.3 (phosphate buffer only for blank). In vitro bile acid binding of various fruits tested on dry matter basis is given in Table II. Relative to cholestyramine for bananas, blueberries, cherries, grapes, peaches, pears, pineapple, plums, prunes and strawberries the bile acid binding of 5–9% is very encouraging, which could be an indicator of their health promoting potential. Similarly 5–9% relative bile acid binding for oat bran and oat bran ready to eat cereal (cereal with US FDA approved for label health claim or lowering cholesterol) have been reported (22, 25). These results (23, 24) indicate that the relative health promoting potentials are: bananas = blueberries > peaches = plums = pineapple = prunes = strawberries ≥ grapes = pears > apricots > nectarines = apples, as indicated by their bile acid binding on a dry matter (dm) basis. The differences in bile acid binding between various fruits tested may relate to their phytonutrients, antioxidants, polyphenols, flavonoids (anthocyanins, flavonols, and proadnthocyanidins), structures, hydrophobicity of undigested fractions, anionic or cationic natures of the metabolites produced during digestion or their interaction with active binding sites. Inclusion of bananas, peaches, pineapple, grapes and pears in our daily diet, as health-promoting fruits should be encouraged. Animal studies are planned to explore relative healthful potential 15 Qian and Rimando; Flavor and Health Benefits of Small Fruits ACS Symposium Series; American Chemical Society: Washington, DC, 2010.
Table I. Composition of apples (Malus sylvestris), apricots (Prunus armeniaca), bananas (Musa paradisiaca), blueberries (Vaccinium spp.), cherries (Malpighia punicifolia), cranberries (Vaccinium macrocarpon), grapes (Vitis spp.), nectarines (Prunus persica, P. nectarina), peaches (Prunus persica), pears (Pyrus communis), pineapple (Ananus comosus), plums (Prunus spp.), prunes (Prunus spp.), and strawberries (Fragaria x ananassa)* Carba
TDF a
Sugar
Plysca
Prota
Fat
Minerals
Apples
95.6
16.6
72.0
23.7
1.8
1.2
1.3
Apricots
81.5
14.7
67.7
13.8
10.3
2.9
5.5
Bananas
91.0
10.4
48.7
42.3
4.3
1.3
3.3
Blueberries
91.8
15.2
63.1
28.7
4.7
2.1
1.5
Cherries
89.5
12.8
89.5
4.7
3.5
2.3
Cranberries
94.8
35.7
31.4
63.4
3.0
1.0
1.2
Grapes
91.7
4.8
86.9
4.8
3.4
1.9
3.0
Nectarines
85.0
13.7
63.6
21.4
8.5
2.6
3.9
Peaches
85.7
13.5
75.4
10.3
8.2
2.2
3.9
Pears
94.9
19.0
60.2
34.7
2.3
0.7
2.0
Pineapple
93.3
10.3
68.4
24.9
4.0
0.9
1.8
Plums
89.4
11.0
77.7
11.7
5.5
2.2
2.9
Prunes
92.5
10.3
55.2
37.3
3.2
0.6
3.8
Strawberries
84.9
22.1
51.5
33.4
7.4
3.3
4.4
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Source
NL
Values are percent based on dry matter. a Carb = Carbohydrate; TDF = Total Dietary Fiber; Plysc = Polysaccharides; Prot = Protein. Polysaccharides = Carbohydrate – Sugar; NL, not listed. Data from refs (23) and (24).
*
for atherosclerosis amelioration (lowering lipids and lipoprotein) and cancer prevention (excretion of toxic metabolites, secondary bile acids) of the fruits studied.
Health Benefits of Consuming Fruits Eight week feeding of diet rich in fruits and vegetables along with low total and saturated fat dairy products to hypertensive subjects with systolic (>140) diastolic (90) mm Hg blood pressure, resulted in the reductions in systolic (11.4) and diastolic (5.5) mm Hg (26). In individuals with base line systolic (131) and diastolic (85) mm Hg blood pressure reductions were systolic (5.5) and diastolic (3.0) mm Hg. For coronary heart disease nine of ten ecological studies, two of three case-control studies and six of 16 cohort studies found a significant protective association with consumption of fruit and vegetables (3). For stroke three of five ecological studies, six of eight cohort studies and for total circulatory 16 Qian and Rimando; Flavor and Health Benefits of Small Fruits ACS Symposium Series; American Chemical Society: Washington, DC, 2010.
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disease, one of two cohort studies reported a significant protective association with consumption of fruit and vegetables. After adjustment for standard cardiovascular risk factors, with the consumption fruits and vegetables, persons in the highest quintile intake had 20% lower relative risk for coronary heart disease compared with those in the lowest quintile of intake. Each 1-serving/d increase in intake of fruits or vegetables was associated with a 4% lower risk for coronary heart disease (27). Mortality data over nineteen years of the NHANES subjects revealed that those consuming fruit and vegetables ≥ 3 times/d compared with
