Eat your fruits and vegetables

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Hi All,

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http://www.hsph.harvard.edu/nutritionsource/fruits.html

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" Eat your fruits and vegetables " is one of the tried and true

recommendations for a healthy diet. And for good reason. Eating

plenty of fruits and vegetables can help you ward off heart disease

and stroke, control blood pressure and cholesterol, prevent some

types of cancer, avoid a painful intestinal ailment called

diverticulitis, and guard against cataract and macular degeneration,

two common causes of vision loss.

What does " plenty " mean? More than most Americans consume. If you

don't count potatoes - which should be considered a starch rather

than a vegetable - the average American gets a total of just three

servings of fruits and vegetables a day. The latest dietary

guidelines call for five to thirteen servings of fruits and

vegetables a day, depending on one's caloric intake.(1) For a person

who needs 2,000 calories a day to maintain weight and health, this

translates into nine servings, or 4½ cups per day.

Over the past 30 years or so, researchers have developed a solid

base of science to back up what generations of mothers preached (but

didn't always practice themselves). Early on, fruits and vegetables

were acclaimed as cancer-fighting foods. In fact, the ubiquitous 5-A-

Day message (now quietly changing to Eat 5 to 9 A Day) seen in

produce aisles, magazine ads, and schools is supported in part by the

National Cancer Institute. The latest research, though, suggests that

the biggest payoff from eating fruits and vegetables is for the heart.

Fruits, Vegetables, and Cardiovascular Disease

There is compelling evidence that a diet rich in fruits and

vegetables can lower the risk of heart disease and stroke.

The largest and longest study to date, done as part of the Harvard-

based Nurses' Health Study and Health Professionals Follow-up Study,

included almost 110,000 men and women whose health and dietary habits

were followed for 14 years. The higher the average daily intake of

fruits and vegetables, the lower the chances of developing

cardiovascular disease. Compared with those in the lowest category of

fruit and vegetable intake (less than 1.5 servings a day), those who

averaged 8 or more servings a day were 30% less likely to have had a

heart attack or stroke.(2)

Although all fruits and vegetables likely contribute to this

benefit, green leafy vegetables such as lettuce, spinach, Swiss

chard, and mustard greens; cruciferous vegetables such as broccoli,

cauliflower, cabbage, Brussels sprouts, bok choy, and kale; and

citrus fruits such as oranges, lemons, limes, and grapefruit (and

their juices) make important contributions.

Increasing fruit and vegetable intake by as little as one serving

per day can have a real impact on heart disease risk. In the two

Harvard studies, for every extra serving of fruits and vegetables

that participants added to their diets, their risk of heart disease

dropped by 4 percent.

Fruits and Vegetables, Blood Pressure, and Cholesterol

High blood pressure is a primary risk factor for heart disease and

stroke. As such, it's a condition that is very important to control.

Diet can be a very effective tool for lowering blood pressure. One of

the most convincing associations between diet and blood pressure was

found in the Dietary Approaches to Stop Hypertension (DASH) study.

(3) This trial examined the effect on blood pressure of a diet that

was rich in fruits, vegetables, and low-fat dairy products and that

restricted the amount of saturated and total fat. The researchers

found that people with high blood pressure who followed this diet

reduced their systolic blood pressure (the upper number of a blood

pressure reading) by about 11 mm Hg and their diastolic blood

pressure (the lower number) by almost 6 mm Hg - as much as

medications can achieve.

Eating more fruits and vegetables can also help lower cholesterol.

In the National Heart, Lung, and Blood Institute's Family Heart

Study, the 4466 subjects consumed on average a shade over 3 servings

of fruits and vegetables a day. Men and women with the highest daily

consumption (more than 4 servings a day) had significantly lower

levels of LDL (bad) cholesterol than those with lower consumption.(4)

How fruits and vegetables lower cholesterol is still something of a

mystery. It is possible that eating more fruits and vegetables means

eating less meat and dairy products, and thus less cholesterol-

boosting saturated fat. Soluble fiber in fruits and vegetables may

also block the absorption of cholesterol from food.

Fruits, Vegetables, and Cancer

Numerous early studies revealed what appeared to be a strong link

between eating fruits and vegetables and protection against cancer.

But because many of these were case-control studies, it is possible

that the results may have been skewed by problems inherent in these

types of studies, such as recall bias and selection bias. Data from

cohort studies that follow large groups of initially healthy

individuals for years have not consistently shown that a diet rich in

fruits and vegetables prevents cancer in general. Data from the

Nurses' Health Study and Health Professionals Follow-up Study support

this finding. Over a 14-year period, men and women with the highest

intake of fruits and vegetables (8+ servings a day) were just as

likely to have developed cancer as those who ate the fewest daily

servings (under 1.5).(2)

A more likely possibility is that fruits and vegetables may

protect against certain cancers. The International Agency for

Research on Cancer, which is part of the World Health Organization,

recently completed a monumental review of the best research on

fruits, vegetables, and cancer. Here's what this 387-page tome

concludes about studies in humans: " There is limited evidence for a

cancer-preventive effect of consumption of fruit and of vegetables

for cancers of the mouth and pharynx, esophagus, stomach, colon-

rectum, larynx, lung, ovary (vegetables only), bladder (fruit only),

and kidney. There is inadequate evidence for a cancer-preventive

effect of consumption of fruit and of vegetables for all other

sites. " (5) However, considering all evidence from human

epidemiological, animal, and other types of studies, it appears that

eating more fruit " probably lowers the risk of cancers of the

esophagus, stomach and lung " and " possibly reduces the risk of

cancers of the mouth, pharynx, colon-rectum, larynx, kidney, and

urinary bladder. " Eating more vegetables " probably lowers the risk of

cancers of the esophagus and colon-rectum " and " possibly reduces the

risk of cancers of the mouth, pharynx, stomach, larynx, lung, ovary

and kidney. "

Keep in mind that this is for total fruit and total vegetable

consumption and that, as pointed out by the International Agency for

Research on Cancer, specific fruits and vegetables may protect

against specific types of cancer. For example, a line of research

stemming from a finding from the Health Professionals Follow-up Study

suggest that tomatoes may help protect men against prostate cancer,

especially aggressive forms of it. (6-8) One of the pigments that

give tomatoes their red hue - lycopene - could be involved in this

protective effect. Although several studies other than the Health

Professionals' study have also demonstrated a link between tomatoes

or lycopene and prostate cancer, others have not or have found only a

weak connection. Taken as a whole, however, these studies suggest

that increased consumption of tomato-based products (especially

cooked tomato products) and other lycopene-containing foods may

reduce the occurrence or progression of prostate cancer. But more

research is needed before we know the exact relationship between

fruits and vegetables, carotenoids, and prostate cancer.(9)

Fruits, Vegetables, and Gastrointestinal Health

One of the wonderful components of fruits and vegetables is their

indigestible fiber. As fiber passes through the digestive system, it

sops up water like a sponge and expands. This can calm the irritable

bowel and, by triggering regular bowel movements, can relieve or

prevent constipation.(10) The bulking and softening action of

insoluble fiber also decrease pressure inside the intestinal tract

and so may help prevent diverticulosis (the development of tiny,

easily irritated pouches inside the colon) and diverticulitis (the

often painful inflammation of these pouches).(11)

Fruits, Vegetables, and Vision

Eating plenty of fruits and vegetables also keeps your eyes in

good shape. You may have learned that the vitamin A in carrots aids

night vision. Other fruits and vegetables help prevent two common

aging-related eye diseases - cataract and macular degeneration -

which afflict millions of Americans over age sixty-five. Cataract is

the gradual clouding of the eye's lens, a disk of protein that

focuses light on the light-sensitive retina. Macular degeneration is

caused by cumulative damage to the macula, the center of the retina.

It starts as a blurred spot in the center of what you see. As the

degeneration spreads, vision shrinks.

Free radicals generated by sunlight, cigarette smoke, air

pollution, infection, and metabolism cause much of this damage. Dark

green leafy vegetables contain two pigments, lutein and zeaxanthin,

that accumulate in the eye. These two appear to be able to snuff out

free radicals before they can harm the eye's sensitive tissues.(12)

In general, a diet rich in fruits, vegetables, and whole grains

appears to reduce the chances of developing cataract or macular

degeneration. (13-15)

The Bottom Line: Recommendations for Fruit and Vegetable Intake

The bottom line: Recommendations for fruit and vegetable intake

Fruits and vegetables are clearly an important part of a good

diet. Almost everyone can benefit from eating more of them, but

variety is as important as quantity. No single fruit or vegetable

provides all of the nutrients you need to be healthy. The key lies in

the variety of different fruits and vegetables that you eat.

Some basic fruit and vegetable tips:

>>Try to eat more fruits and vegetables. If you need 2,000 calories a

day to maintain your weight and health, aim for at least nine

servings (4½ cups) a day.

>>Choose a variety of different fruits and vegetables. It's easy to

get into a rut when it comes to the food you eat. Break out and try a

wider variety - include dark-green, leafy vegetables; yellow, orange,

and red fruits and vegetables; cooked tomatoes; and citrus fruits.

References

1. 2005 Dietary Guidelines for Americans. Center for Nutrition Policy

and Promotion, U.S. Department of Agriculture.

2. Hung HC, Joshipura KJ, Jiang R, et al. Fruit and vegetable intake

and risk of major chronic disease. J Natl Cancer Inst 2004; 96:1577-

84.

3. Appel LJ, TJ, Obarzanek E, et al. A clinical trial of the

effects of dietary patterns on blood pressure. DASH Collaborative

Research Group. N Engl J Med 1997; 336:1117-24.

4. Djousse L, Arnett DK, Coon H, Province MA, LL, Ellison RC.

Fruit and vegetable consumption and LDL cholesterol: the National

Heart, Lung, and Blood Institute Family Heart Study. Am J Clin Nutr

2004; 79:213-7.

5. Vainio H, Bianchini F. IARC Handbooks of Cancer Prevention: Fruit

and Vegetables. Vol. 8. Lyon, France, 2003.

6. Giovannucci E, Ascherio A, Rimm EB, Stampfer MJ, Colditz GA,

Willett WC. Intake of carotenoids and retinol in relation to risk of

prostate cancer. J Natl Cancer Inst 1995; 87:1767-76.

7. Gann PH, Ma J, Giovannucci E, et al. Lower prostate cancer risk in

men with elevated plasma lycopene levels: results of a prospective

analysis. Cancer Res 1999; 59:1225-30.

8. Giovannucci E, Rimm EB, Liu Y, Stampfer MJ, Willett WC. A

prospective study of tomato products, lycopene, and prostate cancer

risk. J Natl Cancer Inst 2002; 94:391-8.

9. Etminan M, Takkouche B, Caamano-Isorna F. The role of tomato

products and lycopene in the prevention of prostate cancer: a meta-

analysis of observational studies. Cancer Epidemiol Biomarkers Prev

2004; 13:340-5.

10. Lembo A, Camilleri M. Chronic constipation. N Engl J Med 2003;

349:1360-8.

11. Aldoori WH, Giovannucci EL, Rockett HR, Sampson L, Rimm EB,

Willett WC. A prospective study of dietary fiber types and

symptomatic diverticular disease in men. J Nutr 1998; 128:714-9.

12. Brown L, Rimm EB, Seddon JM, et al. A prospective study of

carotenoid intake and risk of cataract extraction in US men. Am J

Clin Nutr 1999; 70:517-24.

13. Moeller SM, A, Tucker KL, et al. Overall adherence to the

dietary guidelines for americans is associated with reduced

prevalence of early age-related nuclear lens opacities in women. J

Nutr 2004; 134:1812-9.

14. Cho E, Seddon JM, Rosner B, Willett WC, Hankinson SE. Prospective

study of intake of fruits, vegetables, vitamins, and carotenoids and

risk of age-related maculopathy. Archives of Ophthalmology 2004;

122:883-92.

15. Krinsky NI, Landrum JT, Bone RA. Biologic mechanisms of the

protective role of lutein and zeaxanthin in the eye. Annu Rev Nutr

2003; 23:171-201.

Cheers, Al Pater.