A Fishy Story About Stroke
Abstract & Commentary
Source: He K, et al. Fish consumption and risk of stroke in men. JAMA. 2002;288:3130-3136.
Several previous studies have reported inverse associations between fish intake and the risk of stroke in men1 and women.2 A randomized trial in patients with coronary heart disease, however, found that supplementation with fish oil reduced the risk of acute myocardial infarction but not of stroke.3 Therefore, He and associates prospectively examined the relation between fish intake and risk of stroke in a large cohort of male health professionals who completed dietary measurements in 1986-1998. More than 43,000 men aged 40-75 without diabetes mellitus or symptomatic vascular disease (cerebral, cardiac, or peripheral) at baseline were followed. Fish consumption was computed as the sum of frequency of intake as a main dish of 4 different items: canned tuna fish; dark meat fish such as salmon, swordfish, sardines, etc; other fish; and shrimp, lobster, or scallops. Participants also were asked about the use of fish oil and vitamin supplements and the use of aspirin or antiplatelet agents.
There were 608 strokes during the 12 years of follow-up, including 377 ischemic, 106 hemorrhagic, and 125 unclassified strokes. Compared with men who consumed fish less than once a month, the multivariate relative risk (RR) of ischemic stroke was lower among those who ate fish 1-3 times per month (RR, 0.57; 95% confidence interval [CI], 0.35-0.95). The inverse association between fish intake and risk of ischemic stroke was not modified by the use of aspirin. A higher frequency of fish intake (> once per week) was not associated with further risk reduction. There was no significant association between fish or long-chain omega-3 polyunsaturated fatty acids intake and hemorrhagic stroke; however, the relatively small number of cases means that the possibility that high fish consumption increases risk of hemorrhagic stroke cannot be ruled out.
He et al found that even low fish consumption, at least once a month, was associated with significantly lower risk of ischemic stroke. As they themselves noted, the "biological mechanism of the apparent beneficial effects of such a small amount of fish intake and the lack of a dose response remain unclear." Before we accept these results as proof of the homeopathic method of treating diseases with very small doses of drugs, we should recall as someone wisely said, "Food is never just something to eat." Eating fish frequently may be an indicator of a lifestyle that reduces stroke risk. In fact, He et al reported that men with high fish consumption were less likely to be current smokers or overweight and more likely to be physically active and to use aspirin or multivitamin supplements. They were also more likely to have a history of hypertension and hypercholesterolemia.
Clinicians must continue to interpret recent scientific and unscientific reports linking certain diets and disease prevention. Patients who seek dietary shortcuts to health and fitness must be counseled concerning the role of diet along with medications and physical activity in achieving well-being. An apple a day, a glass of red wine every week, and a tuna fish sandwich every month may all be good but by themselves are unlikely to prevent stroke. — John J. Caronna
Dr. Caronna is Vice-Chairman, Department of Neurology, Cornell University Medical Center; Professor of Clinical Neurology, New York Hospital.
1. Keli SO, et al. Stroke. 1994;25:328-332.
2. Iso H, et al. JAMA. 2001;285:304-312.
3. GISSI-Prevenzione Investigators. Lancet. 1999;354: 447-455.