By how much does fruit and vegetable consumption reduce the risk of ischaemic heart disease?

Objective: To quantify the relationship between fruit and vegetable consumption and the incidence of ischaemic heart disease. Design: A meta-analysis of cohort studies of the relationship between ischaemic heart disease and markers of fruit and vegetable consumption, namely dietary intake of fruit, vegetables, carotenoids, vitamin C, fruit fibre and vegetable fibre, and serum concentration of carotenoids and vitamin C, adjusted for other risk factors. Main outcome measures: Risk of ischaemic heart disease at the 90th centile of consumption relative to that at the 10th, equivalent to about a four-fold difference in fruit consumption and a doubling of vegetable consumption. Results: The association with ischaemic heart disease was of similar magnitude for all six dietary markers of fruit and vegetable consumption. The median of the six estimates was that risk was 15% (range 12-19%) lower at the 90th centile of consumption than at the 10th. The estimates were generally adjusted for the possible confounding effect of other heart disease risk factors. The serum studies of vitamin C were consistent with this; those of carotenoids suggested a larger difference (43%) bur were not adjusted for the important confounding effect of smoking. The substances in fruit and vegetables responsible for the protective effect on heart disease are uncertain but the effect is commensurate with the estimated protective effects of the potassium and folate in fruit and vegetables. Beta-carotene or vitamin E are not likely to be important because randomised trials of these vitamins in large doses have shown no reduction in heart disease mortality. Conclusions: The risk of ischaemic heart disease is about 15% lower at the 90th than the 10th centile of fruit and vegetable consumption.