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MONDAY, July 19 (HealthDayNews) -- Take it to heart: A diet rich in baked or broiled fish may protect against atrial fibrillation, a potentially dangerous cardiac condition.

According to a new study, eating broiled or baked fish reduces your chances of developing this common irregular heartbeat. However, eating fried fish or fish sandwiches does not carry the same benefits.

"Eating tuna or other fish that is broiled or baked is associated with a lower risk of atrial fibrillation, which is a very common heart rhythm abnormality, especially among elderly people," said study author Dr. Dariush Mozaffarian, a researcher at the Channing Laboratory at Brigham and Women's Hospital and an instructor of medicine at Harvard Medical School.

Mozaffarian's team collected data on 4,815 men and women over 65 who participated in Cardiovascular Health Study, funded by the National Heart, Lung, and Blood Institute. As part of the study, subjects reported what they ate each day.

During 12 years of follow-up, there were 980 cases of atrial fibrillation among the study particpants.

Compared with those who ate fish only once a month or less, individuals who ate fresh or canned tuna or other broiled or baked fish two to four times per week had a 28 percent lower risk of developing atrial fibrillation.

Moreover, those who ate fish five times a week or more lowered their risk of atrial fibrillation by 31 percent, according to the report in the July 20 online issue of Circulation.

"However, fried fish was not associated with lower risk of atrial fibrillation. In fact, there were signs of higher risk," Mozaffarian said.

More than 2 million Americans suffer from atrial fibrillation -- a chronic condition that can cause fatigue and shortness of breath.

It happens when the two upper chambers of the heart (the atria) beat irregularly. When this happens, blood doesn't get pumped completely out of the atria, and may pool and clot. Should a blood clot leave the heart, it can block an artery in the brain, causing a stroke.

Of all strokes, about 15 percent to 20 percent happen in people with atrial fibrillation. The risk of atrial fibrillation increases with age, increasing by about 2 percent each year after age 65.

Mozaffarian believes the protective effect of fish is related to fish oil, which contains omega-3 fatty acids. "There are lots of effects of omega-3 fatty acids that could favorably influence the risk of atrial fibrillation," he said.

"Diet may influence this common heart rhythm abnormality, but more study needs to be done. It's too early to translate these findings into dietary recommendations," Mozaffarian noted.

Mozaffarian added there is evidence that eating fish is good for the heart and can protect you from a variety of heart problems, and atrial fibrillation may be another example.

Dr. Randall S. Stafford, an assistant professor of medicine at the Stanford Center for Research in Disease Prevention at Stanford University, said, "This finding is consistent with what has been published about the impact of omega-3 fatty acids on other cardiovascular endpoints."

Stafford noted a causal relationship between eating fish and preventing atrial fibrillation was not found. "There may be other factors that cause the broiled or baked fish-eating population to be different from the population that uses that food less frequently," he said.

There is a relationship between the development of heart disease and atrial fibrillation, Stafford said: "It may be that these findings are consistent with that link."

"If you prevent the early stages or the progression of atherosclerosis in the heart, you may not only protect it from heart attack or angina, you could also prevent other events such as atrial fibrillation," he added.

Preventing atrial fibrillation may be another benefit of the already well-known heart benefits of eating fish, Stafford said.

"If you prevent the occurrence of atrial fibrillation, you have a chance of preventing some strokes," he said. "It is a complicated process to try to prevent strokes once somebody has atrial fibrillation."

More information

The Atrial Fibrillation Foundation can tell you about atrial fibrillation.

(SOURCES: Dariush Mozaffarian, M.D., M.P.H., instructor, medicine, and researcher, Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Harvard School of Public Health, Boston; Randall S. Stafford, M.D., Ph.D., assistant professor, medicine, Stanford Center for Research in Disease Prevention, Stanford University, California; July 20, 2004, Circulation online)

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