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Study: Eating fish reduces stroke risk

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(CNN) -- Eating two or more servings of fish a week -- already known to be good for your heart -- cuts the risk of having a a certain kind of stroke by half, according to a new study of almost 80,000 women.

The study, conducted at the Harvard School of Public Health and published in this week's Journal of the American Medical Association, also found that women who ate five or more servings of fish a week had one-third the risk of having a type of stroke known as a thrombotic infarction compared to women who ate fish once a month or less.

"I wasn't surprised by the direction of this study, but I was surprised by the magnitude," said Dr. Meir Stampfer, professor of epidemiology and nutrition at the Harvard School of Public Health and a co-author of the study. "I didn't expect the protective effect of fish to be that strong."

Dr. Stampfer said even though the study was just in women, the results most likely apply to men, too.

The study authors theorize that fish reduces the risk of stroke because the fat in it, called omega-3 polyunsaturated fatty acids, makes the blood clot less easily. Thrombotic infarctions are caused by impaired blood flow to the brain because of a clot in one or more of the arteries supplying blood to the brain.

The study found fish consumption made no difference in the risk of having a hemorrhagic stroke, which is caused by a breakage in the blood vessel. Hemorrhages can be caused by a number of disorders, including weak spots on the blood vessel wall which are usually present since birth.

"It makes sense that eating fish would help against [thrombotic infarctions] and not hemorrhagic strokes," said Dr. Lawrence Brass, professor of neurology at Yale University Medical School and a spokesman for the National Stroke Association.

It's unclear whether eating fish oil supplements would also help against strokes. Studies have shown they protect against some forms of heart disease, just as fish does.

Dr. Brass said while he was impressed with the study, he had some concerns about the it.

He said he wondered if fish-eaters might have some other feature in common that would protect against strokes.

The researchers said women in the study who ate more than two servings of fish a week also were more likely to exercise, eat less red meat, and be non-smokers, but that they statistically controlled for these differences.

Dr. Brass said there might be some other factor, unknown to researchers, that explained the difference. "Perhaps fish tastes better with rice than with potatoes and it's the rice that makes the difference [in strokes]. We don't know now, but this study points us in the right direction.

"I would tell patients, if you like fish, and can fit it into your diet, eat a little less red meat and eat fish instead," he said. "It can't hurt you. It's not like telling someone to take a drug that's expensive and has serious side effects."

But he added there are exceptions to his advice. Last week, the U.S. Food and Drug Administration warned pregnant women, women of childbearing age who may become pregnant, nursing mothers and young children not to eat shark, swordfish, king mackerel and tilefish. These fish contain high levels of a form of mercury called methyl mercury that may harm an unborn baby's developing nervous system, according to the FDA.

Last year, the American Heart Association recommended that people eat two servings a week of fatty fish like tuna or salmon to prevent heart disease.

Dr. Robert Eckel, head of the AHA's nutrition committee, said he was impressed with the stroke study, but concerned about how to get people to eat fish.

"It'll be a big task," he said. "A lot of people, especially in the middle part of the country, aren't used to eating a lot of fish. A lot of people just haven't had fish prepared in a way that's good."



RELATED STORIES:
Heart experts' advice: Eat more fish in a balanced diet
October 5, 2000
Research points to 'Mediterranean' diet to help prevent repeat heart attack
February 15, 1999
Researchers: Fat in the diet may affect mental ability
September 4, 1998
Study: Seafood combats cardiac arrest
November 1, 1995

RELATED SITES:
American Heart Association - Fish Consumption, Fish Oil, Lipids, and Coronary Heart Disease
FDA Center for Food Safety and Applied Nutrition - Omega-3
The Nurse's Health Study - Brigham and Women's Hospital
The Fish Foundation - Omega-3 Fatty Acids
UCLA - Effects of Omega-6 and Omega-3 Polyunsaturated Fatty Acids on Breast Cancer
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