A new U.S. medical study shows that eating just a small amount of fish each month can dramatically lower the risk of stroke.

That fish is healthy for your circulatory system is no surprise. Many studies over the years have found that stroke and heart disease rates are lower among people who make fish a regular part of their diet. Just look at Iceland and Japan, where fish consumption is the highest per person in the world. People in those countries have the lowest death rates from stroke and heart disease and, in fact, from all causes of mortality.

With the benefits of fish well known, a question has remained about how much fish consumption is necessary to achieve them.

A study in the Journal of the American Medical Association shows that very little is necessary at least to prevent stroke.

"There seemed to be no benefit in eating fish very frequently," said physician Albert Ascherio. Dr. Ascherio and colleagues at the Harvard University School of Public Health examined the diets of more than 40 thousand men aged 40-75 over 12 years. They found that eating just two small servings of fish each month reduces the risk of stroke significantly.

So eating fish just a few times per month was just as good as eating fish almost every day. Men who consumed fish two times a month or more had almost half the risk of stroke as compared with men who never ate fish.

This study, like others before it, shows that eating fish reduces the kind of stroke caused by blood clots. It did not show that eating fish reduces the other kind of stroke, which occurs when there is bleeding into the brain as the result of a burst blood vessel.

Fish helps because its fatty acids make your blood flow more freely, helping prevent the formation of blood clots.

But what kind is best at preventing stroke? Dr. Ascherio cannot say.

"Our study did not look at the specific type of fish. We can only conclude that eating fish in general is likely to be beneficial to prevent stroke," he said.

The Harvard doctor said eating a variety of seafood is the best course of action.

The finding that small amounts are beneficial is good news to people like Jim Leadhem, who are not fish fans. "I never was a big fan of fish but I'm trying to learn more about the different kinds and try to eat more fish on a regular basis," he said.