Men who eat just one serving of fish a month may have a lower risk of the most common type of stroke, which occurs when blood flow to the brain becomes blocked, new study findings from Harvard University indicate.
However, eating more fish may not add much benefit when it comes to lowering the risk of hemorrhagic stroke, which is caused by bleeding in the brain.
In the study of more than 43,000 men aged 40 to 75 years, eating fish one to three times a month was associated with a 43% lower risk of ischemic stroke. But men who reported eating fish at least five times a week were only slightly more protected, with a 46% lower risk.
Exactly how such a small amount of fish, which is rich in long-chain omega-3 polyunsaturated fatty acids (PUFAs), may lower stroke risk is not clear.
However, omega-3 fatty acids may have several different effects on the body, including a reduction in the "stickiness" of platelets, which help form blood clots. Because clots are the cause of 80% of strokes, preventing them from forming may ward off strokes.
The study adds to a growing body of research into the effect of fish on stroke risk. One recent report found that women who ate at least five servings of fish a week had a 62% lower risk of stroke, compared with those who ate fish less than once a month.
The researchers followed men taking part in the Health Professional Follow-up Study, a large national trial. The men in the study, who did not have heart disease or diabetes at the outset, filled out detailed questionnaires about their usual diets.
Over the next 12 years, the researchers documented 608 strokes, including 377 ischemic strokes and 106 hemorrhagic strokes. They found no association between fish consumption and this rare type of stroke.
Men who consumed the most fish were less likely to smoke or to be overweight, and more likely to exercise and take multivitamin supplements. These men were also more likely to report a history of high blood pressure and high cholesterol, the study found.
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