Diet and Ischemic Stroke
November 1, 1999 3 minutes read
Diet and Ischemic Stroke
Abstract & Commentary
Synopsis: Patients should focus on consuming fruit and vegetables and not try to replace them with dietary supplements.
Source: Joshipura KJ, et al. JAMA 1999;282:1233-1239.
The nurses’ health study continues to provide helpful data on women’s health trends. In this prospective cohort study, Joshipura and colleagues from Harvard followed the dietary intake of 75,596 healthy nurses aged 34-59 from 1980 to 1994. (They also followed a similar male cohort from the Health Professionals’ Follow-Up Study.) Both cohorts responded to surveys every two years to indicate their dietary and other health habits (with extensive food frequency questionnaires), as well as their incidence of cardiovascular disease and other health outcomes. For respondents who reported strokes, Joshipura et al reviewed medical records and imaging studies to verify the diagnoses.
Of the large cohort in the Nurses’ Health Study, 366 women eventually suffered new ischemic strokes. It turned out that the women in the highest quintile for intake of fruit and vegetables (with a median of 5.8 servings daily) had a relative risk of ischemic stroke of 0.74 (95% CI 0.52-1.05) compared with women in the lowest quintile. Each daily serving of fruits or vegetables appeared to lower women’s ischemic stroke risk by 7%, with the greatest effect seen with green leafy vegetables, cruciferous vegetables, and citrus fruit (including juices). Only legumes and potatoes appeared to confer no benefit. These statistically significant findings persisted after investigators controlled for smoking and other cardiovascular risk factors, for fat intake, and for use of multivitamins and other nutritional supplements. The men’s cohort produced similar results.
Comment by Elizabeth Morrison, MD, MSEd
Stroke affects half a million people every year, many of them women. Fortunately, those of us who provide primary care have opportunities to counsel women about lifestyle modifications that can make a difference. I enjoy finding articles like this one by Joshipura et al because they give me interesting new perspectives to share with patients when discussing dietary recommendations for health maintenance.
For prevention of coronary artery disease, the American Heart Association already recommends that all Americans consume a balanced diet emphasizing antioxidant-rich vegetables, fruits, and whole grains rather than specific antioxidant supplements.1 We can now tell female patients that such a diet appears to prevent ischemic stroke as well. Current recommendations that patients consume at least five daily servings of fruit and vegetables appear to be right on the mark.
Joshipura et al discussed current evidence, they suggested mechanisms through which fruit and vegetables (particularly of the green, leafy, cruciferous, or citrus varieties) would prevent ischemic stroke—dietary flavonoids, folate and its effect on serum homocysteine, fiber, and potassium. They concluded that the data support no single mechanism. The important point from this study and others is that patients should focus on consuming fruit and vegetables and not try to replace them with dietary supplements.
Since this study is not a randomized, controlled trial, it is naturally subject to confounding factors. For example, women who consume more fruit and vegetables might also exhibit other health-promoting behaviors that limit ischemic stroke. Yet, when Joshipura et al painstakingly controlled for a multitude of possible confounders, the apparent benefit of fruit and vegetable intake persisted. Joshipura et al also note that their cohorts are fairly homogenous in terms of occupation and socioeconomic status, minimizing the risk that socioeconomic factors confounded the results. However, it would be interesting in future studies to see how dietary factors interact with ischemic stroke risk among populations of lower socioeconomic status. (Dr. Morrison is Director of Maternity Care Education, Assistant Clinical Professor of Family Medicine, University of California, Irvine.)
Reference
1. Tribble DL, et al. Circulation 1999;99:591-595.
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