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Evidence-Based Eating

Trying to make sense of diet and health has not been helped by the apparently divergent views that have been published over the years. To find some solid evidence with large effects from a reputable source is particularly welcome.

Fruit & veg prevent stroke in men

From the Framingham study, a cohort study of 832 middle aged men has examined the effects of eating fruit and vegetables on the risk of stroke. They were free of cardiac disease at the start of the study, which had a 20-year follow-up.

Design of the study

The diet of each subject was assessed at baseline from a single 24-hour recall. The estimated number of servings of fruits and vegetables was used to differentiate the men into five groups (quintiles) of increasing vegetable intake. The intake of the lowest group was 0-2 servings a day, that of the middle group was 5 servings a day, while that of the group with the highest intake was 8-19 servings a day (mean 10 ).

A serving was defined, roughly, as 120 mL (half a cup) for fruits and vegetables, 60 mL for tomato sauce, 120 mL for peas, beans and corns, 28g or potato chips (crisps), or a single potato.

During a follow-up period of 18-22 years all cardiovascular events, including stroke, were reviewed by a panel of three physicians who used a set of established criteria. For stroke outcomes the panel included at least two experienced neurologists. Minimal criteria for stroke included abrupt onset of a localised neurological deficit. Stroke was further characterised into ischaemic, or haemorrhagic stroke. Transient ischaemic attacks (TIA) were recorded separately

Results

Despite the large differences in diets, there were few differences between the men in the five groups (mean age 56 years at baseline) for systolic blood pressure, serum cholesterol, ethanol intake or physical activity index. Men with the largest fruit and vegetable index tended to have a slightly higher body mass index and they smoked fewer cigarettes and had a higher energy intake.

As the number of servings of fruit and vegetables increased, the number of stroke events decreased. In men eating the lowest amount of fruit and vegetables, 19 of 100 had a stroke compared with only 8 of 100 among men eating the highest amount. Similarly the number of completed strokes fell by nearly two thirds from nearly 15 of 100 to 6 of 100 from low to high fruit and vegetable intake.

What is the mechanism?

There doesn't seem to be a satisfactory answer to this. The authors looked for all sorts of confounding variables, and their discussion is interesting in itself, but there seems to be a protective effect of fruit and vegetables against stroke.

Take home message

Eating quite moderate amounts of fruit and vegetables can substantially reduce the risk of a stroke.

Reference:

MW Gillman, LA Cupples, D Gagnon et al. Protective effect of fruits and vegetables on development of stroke in men. Journal of the American Medical Association 1995 273: 1113-7.




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