BOSTON, MASSACHUSETTS. Several studies have shown that regular fish consumption helps protect against stroke. It is not clear, however, whether fish consumption protects against both ischemic stroke (stroke caused by a blood clot) and hemorrhagic stroke (stroke caused by a burst blood vessel). Researchers at the Harvard School of Public Health have now released the results of a major study designed to answer this question.
The study involved 43,671 male health professionals aged 40 to 75 years when enrolled in 1986. During a 12-year follow-up period 608 strokes occurred (377 ischemic, 106 hemorrhagic, and 125 strokes of unknown origin). The annual stroke rate in this group is clearly remarkably low at 0.1% overall and 0.07% for ischemic stroke. The participants completed food frequency questionnaires in 1986, 1990 and 1994. Men who consumed fish at least once a month had a 44% lower risk of having an ischemic stroke than did men who consumed fish less than once per month. No significant associations were found between fish or long chain omega-3 PUFA (polyunsaturated fatty acid) intake and the risk of hemorrhagic stroke, but a possible association could not be ruled out due to the relatively small number of hemorrhagic strokes that occurred in the group.
The optimum protection was achieved at fish consumption once per week and more frequent fish consumption (5 or more times per week) did not reduce stroke risk further. The protective effect of fish consumption was not significantly affected by the use of aspirin or vitamin E supplements (about 25% of participants used aspirin for stroke protection and about 20% supplemented with vitamin E). The researchers calculated the intake of PUFAs (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) from fish and found that significant protection against ischemic stroke was achieved at a daily fish oil intake of between 50 mg and 200 mg. The level of daily intake of alpha-linolenic acid did not affect stroke risk. Additional fish oil supplementation did not reduce risk of ischemic stroke any further.
He, K, et al. Fish consumption and risk of stroke in men. Journal of the American Medical Association, Vol. 288, December 25, 2002, pp. 3130-36