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Etiology

Fruit and vegetable intake reduced the risk for stroke in middle-aged men

ACP J Club. 1995 Nov-Dec;123:78. doi:10.7326/ACPJC-1995-123-3-078


Source Citation

Gillman MW, Cupples LA, Gagnon D, et al. Protective effect of fruits and vegetables on development of stroke in men. JAMA. 1995 Apr 12;273:1113-7.


Abstract

Objective

To determine whether an association exists between fruit and vegetable intake and the risk for stroke among middle-aged men.

Design

20-year cohort analytic study of participants in the Framingham Study.

Setting

Population-based study of men in Framingham, Massachusetts, USA.

Participants

832 men (age range 45 to 65 y, mean age 56 y) who were free of cardiovascular disease at baseline in 1966 to 1969.

Assessment of risk factors

At baseline, dietary information was obtained by trained interviewers using a single 24-hour diet recall. Foods were categorized on the basis of similarities in their energy content and macronutrient composition. There were 3 groups of fruits (watery, average, and sweet) and 10 categories of vegetables (roots and fruits, raw and green, cooked leafy, tomato sauce, peas and lima beans, baked beans, corn, potatoes, sweet potatoes, and potato chips).

Main outcome measures

Completed strokes and transient ischemic attacks (TIAs) diagnosed by patient history review, surveillance of hospital discharge data, and communication with family physicians and relatives and confirmed by a physician-investigator panel using established criteria.

Main results

97 incident cardiovascular events occurred during follow-up: 73 completed strokes and 24 TIAs. For each increment of 3 daily servings of fruits and vegetables, the risk for all stroke, including TIA, decreased by 22% (age-adjusted relative risk [RR] 0.78, 95% CI 0.62 to 0.98). The RR was 0.74 (CI 0.57 to 0.96) for completed stroke, 0.76 (CI 0.57 to 1.02) for completed stroke of ischemic origin, and 0.49 (CI 0.25 to 0.95) for completed stroke of hemorrhagic origin. Adjustment for cigarette smoking; glucose intolerance; body mass index; left ventricular hypertrophy; physical activity index; serum cholesterol level; systolic blood pressure; age; and intake of total energy, ethanol, and fat did not substantially change the results.

Conclusion

Fruit and vegetable intake decreased the risk for stroke among middle-aged men.

Sources of funding: National Institutes of Health; Harvard Medical School; Harvard Community Health Plan Foundation.

For article reprint: Dr. M.W. Gillman, Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, 126 Brookline Avenue, Suite 200, Boston, MA 02215, USA. FAX 617-859-8112.


Commentary

Increasing fish intake did not reduce the risk for coronary disease in men

The well-written reports by Gillman and Ascherio and their colleagues show that the Framingham Study, which was started in 1948, and the Health Professionals' Follow-up Study, which was started in 1986, continue to produce important results.

The study by Gillman and colleagues on fruits and vegetables and strokes supplements our mother's advice: It may take more than 1 apple a day to keep the doctor away! The authors note that, for each increment of increased intake of fruits and vegetables, a corresponding decrease occurred in the risk for cerebrovascular events.

The measurement of "exposure"—fruit and vegetable consumption at baseline—was based on a single 24-hour recall, which may be an imperfect reflection of a person's usual diet. An in-depth dietary assessment, such as multiple 24-hour food recalls, food records, or food frequency questionnaires, would have provided more meaningful information at both a macro- and micro-nutrient level and would have increased our confidence in ascribing the proposed benefit to the exposure.

The investigators considered all known confounders and, even after adjusting for smoking, the protective effect of fruit and vegetables on stroke incidence remained statistically significant. As in all observational studies, however, unknown confounders cannot be expected to be balanced between the cohorts and may influence the final result. Therefore, it is unclear whether it is the lifestyle or associated factors in persons who eat more fruit and vegetables or the foods themselves that offer protection from stroke. Although this study included only men, the protective effect of fruits and vegetables and lifestyle factors probably extends to women.

The article by Ascherio and colleagues is a report of a large cohort study from the Harvard group that suggests that increasing fish in the diet does not reduce the risk for coronary heart disease (CHD) in U.S. men of high socioeconomic status. The authors note, however, that the group eating no fish had the highest rate of cardiac events. Other primary prevention studies on this topic conflict (1-4). The beneficial vascular effects of omega n-3 fatty acids in fish may depend on serum eicosapentaenoic (EPA) and ocosahexaenoic (DHA) acids. Neither the serum levels of these active ingredients nor the methods of cooking the fish, which may affect the activity of these ingredients, were reported. A recent U.S. case-control study showed that the average U.S. consumption of fish did not result in substantial levels of EPA and DHA; this may have been because of the type of fish consumed or because of its preparation (5). Because this study also used a cohort design, confounding is possible. For example, men who ate more fish also appeared to be at higher risk for CHD (increased family history of CHD and cholesterol), were aware of this, led healthier lifestyles (which included increased exercise and consumption of fiber, fruit, vegetables, and vitamins), and had more cardiovascular bypass grafting.

Whether or not "a fish a day keeps the doctor away" is valid, studies from various sources point to the benefits of increasing fruits and vegetables in the diet of most persons. This is consistent with articles that suggest that increasing consumption of fiber and antioxidants may be beneficial to cardiovascular health.

Sonia Anand, MD
McMaster UniversityHamilton, Ontario, Canada
Stephen R. Yarnall, MD
Edmonds, Washington, USA


References

1. Kromhout D, Bosschieter EB, de Lezenne Coulander C. The inverse relation between fish consumption and 20-year mortality from coronary heart disease. N Engl J Med. 1985;312:1205-9.

2. Shekelle RB, Missell LV, Paul O, Shyrock AM, Stamler J. Fish consumption and mortality from coronary heart disease [Letter]. N Engl J Med. 1985;313:820.

3. Vollset SE, Heuch I, Bjelke E. Fish consumption and mortality from coronary heart disease [Letter]. N Engl J Med. 1985;313:820-1.

4. Norell SE, Ahlbom A, Feychting M, Pedersen NL. Fish consumption and mortality from coronary heart disease. Br Med J (Clin Res Ed). 1986;293:426.

5. Guallar E, Hennekens CH, Sacks FM, Willett WC, Stampfer MJ. A prospective study of plasma fish oil levels and incidence of myocardial infarction in U.S. male physicians. J Am Coll Cardiol. 1995;25:387-94.