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FRUITS, VEGETABLES, AND CORONARY HEART DISEASE IN WOMEN

(August 2002)

Fruits and vegetables are good for you. High intake appears to reduce the risk of coronary heart disease, stroke, and certain cancers. The questions that remain unanswered are:

None of these questions is adequately answered. For cancer prevention, probably vegetables are more important than fruits, particularly the cruciferous vegetables (cabbage, broccoli, brussel sprouts, cauliflower).

The confusion is shown by three studies from groups at Harvard with overlapping authors.

The most recent study in the Archives of Internal Medicine in August 2001 is from the renowned Nurses’ Health Study. They studied 69,017 women ages 38 to 63 years. Those following a prudent diet (higher fruits and vegetables, legumes, fish, poultry, whole grains) were compared with those following a western diet (more red and processed meats, sweets, desserts, french fries, refined grains) in regard to coronary heart disease occurrence over a twelve-year period.

The women were divided into five groups (quintiles) according to a score indicating adherence with either the prudent or western diet. Those in the two highest groups for adherence to the prudent diet had a 24 percent reduction in coronary heart disease events. Those in the top group for the bad (western) diet had a 46 percent increased risk. In general, only the top groups (highest intakes) for the good diet (prudent) or bad diet (western) decreased or increased the risk of coronary heart disease. And, those who followed the "good" diet were likely to be healthier in several other respects - they smoked less, took more vitamin supplements, took more folic acid, etc.

The authors concluded "this study indicates that a diet high in fruits, vegetables, legumes, whole grains, poultry, and fish and low in red and processed meats and refined grain products may lower the risk of coronary heart disease in women". The number of servings of fruits and vegetables in this and a similar study by the same group in men was more than five servings a day.

The second study appeared in October 2000. This time, the group studied was 39,876 female health professionals who were followed for five years. Those women who ate more fruits and vegetables had a reduced risk of heart attacks. Here again, the women who ate more fruits and vegetables were healthier - smoked less, took more vitamins, exercised more. Again, the women were divided into five groups (quintiles). The top intake group (ten or more portions a day) had a 37 percent reduction in risk of a heart attack, but this was not statistically significant. BUT, the greatest benefit was for the second to lowest quintile. They ate only four portions of fruits and vegetables, but had a 55 percent, statistically significant, reduction in risk of heart attacks. So, in this study, unlike the Nurses’ Health Study, only a modest intake was beneficial.

The authors concluded "these findings support current dietary recommendations to increase the intake of fruits and vegetables as a preventive measure against cardiovascular disease".

The third paper appeared in November 2000 in the American Journal of Clinical Nutrition. It analyzed the benefits of adhering to dietary guidelines that urged more fruits and vegetables and the prudent diet. Here, the Nurses’ Health Study data were used. A 14 percent statistically non-significant reduction in cardiovascular disease (including heart attacks) was found in the group adhering most to the recommendations (consuming more than nine servings per day).

The authors concluded "these data suggest that adherence to the Dietary Guidelines for Americans will have limited benefit in preventing major chronic disease in women. We observed a small decrease in cardiovascular disease".

Commentary: In these three reports from essentially the same group of investigators from the same institution, you can reasonably conclude:

These are very good investigators, but the compulsion to overwhelm the medical literature with huge numbers of papers, each claiming authoritative results, has its drawbacks. Some of what is published will turn out to be valid and important, some will not hold up, and, as in this case, some will be contradictory and produce confusion. One problem with this kind of study is that, often, dietary patterns are determined once or over a brief period of time and the investigators assume that dietary patterns were similar before the actual assessment and will stay constant subsequently. However, dietary patterns are often not that constant.

for the benefit of a good intake of fruits and vegetables.

But, we still do not know which fruits and vegetables produce the most benefit, and we do not know the number of portions required each day. At present, the safest approach would seem to be to try to include at least four or five portions of fruits and vegetables a day. The evidence suggests strongly that the benefit of a high fruit, high vegetable diet in prevention of heart attacks is modest. That, in turn, means you must pay attention to the major risk factors for coronary heart disease and heart attacks:

That is why Healthful Life urges regular prevention examinations to check on these major risk factors..

Fung, T.T., et al. Dietary patterns and risk of coronary heart disease in women. Archives of Internal Medicine. Vol 161 (August 13) Pgs 1857-1862. 2001.

Liu, S., et al. Fruit and vegetable intake and risk of cardiovascular disease: The women’s health study. American Journal of Clinical Nutrition. Vol 72 (October) Pgs 922-928. 2000.

McCullough, M.L., et al. Adherence to dietary guidelines for Americans and risk of major chronic disease in women. American Journal of Clinical Nutrition. Vol 72 (November) Pgs 1214-1222. 2000.

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