Evidence that fruit and vegetable consumption protects human health is accumulating from large population (epidemiological) studies, human feeding studies, and cell culture studies. Listed below are a few selected population studies from the literature linking fruit and vegetable consumption to health. For an excellent review concerning vegetables, fruit and cancer prevention, see Steinmetz and Potter, Journal of the American Dietetic Association 1996;96:1027.
See the World Cancer Research and American Institute for Cancer Research 10 year study on Food, Nutrition, and the Prevention of Cancer: a Global Perspective.
Evidence that Carotenoids are Protective
Fruit and vegetable consumption has been linked to decreased risk of stroke — both hemorrhagic and ischemic stroke. Each increment of three daily servings of fruit and vegetables equated to a 22% decrease in risk of stroke, including transient ischemic attack (Gillman et al. Journal of the American Medical Association. 1995;273;1113).
Elderly men whose intake of dark green and deep yellow vegetable put them in the highest quartile for consumption of these vegetables had about a 46% decrease in risk of heart disease relative to men who ranked in the lowest quartile. Men in the highest quintile had about a 70% lower risk of cancer than did their counterparts in the lowest quintile. The differences in vegetable consumption between high and low intake rankings was not striking. Men in the highest quartile or quintile consumed more than two (>2.05 and >2.2) servings of dark green or deep yellow vegetable a day; those in the lowest quartile or quintile consumed less than one serving daily (<0.8>
Consumption of tomato products has been linked to decreased risk of prostate cancer. Men in the highest quintile for consumption of tomato products (10 or more servings a week) had about a 35% decrease in risk of prostate cancer compared to counterparts whose consumption put them in the lowest quintile (1.5 or fewer servings of tomato products a week) (Giovannucci et al. Journal of the National Cancer Institute 1995;87:1767).
People in the highest quintile for consumption of spinach or collard greens, plants high in the carotenoid lutein, had a 46% decrease in risk of age-related macular degeneration compared to those in the lowest quintile who consumed these vegetables less than once per month (Seddon et al. Journal of the American Medical Association. 1994;272:1413).
Evidence that Polyphenols are Protective
Flavonoid consumption has been linked to lower risk of heart disease in some, but not all, studies. Elderly Dutch men in the highest tertile of flavonoid intake had a risk of heart disease that was about 58% lower than that of counterparts in the lowest tertile of intake. Those in the lowest tertile consumed 19 mg or less of flavonoids per day, whereas those in the highest tertile consumed approximately 30 mg per day or more (Hertog et al. Lancet. 1993;342:1007). Similarly, Finnish subjects with the highest quartile of flavonoid intake had a risk of mortality from heart disease that was about 27% (for women) and 33% (form men) lower than that of those in the lowest quartile (Knekt et al. British Medical Journal. 1996;312:478).
However, in other studies the protective effect of flavonoids could not be confirmed. For Welch men, flavonol intake did not predict a lower rate of ischemic heart disease and was weakly positively associated with ischemic heart disease mortality (Hertog et al. American Journal of Clinical Nutrition. 1997;65:1489). For U.S. male health professionals, data did not support a strong link between intake of flavonoids and coronary heart disease (Rimm et al. Annals of Internal Medicine. 1996;125:384).
