By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

Several studies have indicated that eating fish may lower the chances of having a heart attack, and it has been suggested that this can be attributed to the effects of omega-3 polyunsaturated fatty acids, which are a major ingredient of fish oils. They tend to inhibit blood clotting.

A sample of 6299 Americans was surveyed between 1971 and 1975, with an evaluation of their food intake, as part of the National Health and Nutrition Examination Survey (NHANES). They were then followed for 12 years. In white women it was found that there was a close relationship between the consumption of fish and the likelihood of having a stroke-- women who ate the most fish had the fewest strokes. The same relationship was found in black men and women, but not in white men.

Doctor's comments

The protective effect of eating fish was first suspected in studies of Eskimos, who eat a high-fat diet but have little heart disease. Heart attacks occur because a blood clot forms in a coronary artery, and when the same thing happens in a cerebral artery, the result is a stroke (technically referred to as a thrombotic stroke). Unlike heart attacks, however, strokes can also occur from a bleed into the brain (hemorrhagic stroke), although these are less common. While fish oils may protect against thrombotic strokes, it has been observed that Eskimos have a relatively high incidence of hemorrhagic strokes. This study was not able to separate the two kinds of stroke. It is puzzling why the protective effect of fish was apparent in white women but not men, but one previous study did report an effect in men.

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