The role of folate, antioxidant vitamins and other constitutents in fruit and vegetables in the prevention of cardiovascular disease: The epidemiological evidence

Evidence that fruit and vegetables may protect against coronary heart disea se is accumulating. It is unclear which constituents of fruit and vegetable s are responsible for this protective effect. Folate as a co-substrate in h omocysteine metabolism may be important. An intake of about 400 mug folate equivalents/day seems to be required to achieve stable low homocysteine blo od levels. Five of eight epidemiologic studies show significant inverse ass ociations between folate and cardiovascular disease. These associations cou ld be confounded by antioxidant vitamins and/or other substances. In trials examining an association between folate and cardiovascular disease such co nfounding must be excluded, before specific recommendations can be given. O bservational studies suggest that vitamin C plays a role in the aetiology o f cardiovascular disease, but there are no completed intervention trials of this vitamin alone. With regard to vitamin E two cohort studies point to c ardiovascular benefits with the long-term use of supplements of at least 10 0 IU/day, but the results of controlled trials are inconclusive. There is s ome evidence from observational studies of an inverse association between b eta -carotene and cardiovascular disease, particularly in smokers. Interven tion trials do not support this hypothesis, rather, they suggest a possible harmful effect of beta -carotene supplements in smokers. Nevertheless, pro tective effects of beta -carotene and vitamin E in different dosages, durat ions of administration, or different combinations, are still possible. The last paragraph of this review discusses limitations of the present and prio rities of future research.