April 22 (HealthDay News) -- Men who consume fatty fish and marine omega-3 fatty acids appear to have a reduced risk of heart failure, a new study has found.

Between 1998 and 2004, U.S. and Swedish researchers followed nearly 40,000 Swedish men, ages 45 to 79, recorded details of their diets and tracking their health outcomes. During that time, 597 men with no history of heart disease or diabetes developed heart failure, and 34 of them died from the disorder.

Men who ate fatty fish -- such as salmon, mackerel, herring, whitefish and char -- once a week were 12 percent less likely to develop heart failure than men who never ate fatty fish. The study also found that men who consumed a moderate amount (about 0.3 grams a day) of omega-3 fatty acids -- found in cod liver oil and other fish oils -- were less likely to develop heart failure than those who consumed little or no omega-3 fatty acids.

The beneficial heart effect was seen only in men who ate about one serving of fatty fish a week and who had a moderate intake of marine omega-3 fatty acids. Men who consumed more fatty fish or omega-3 fatty acids did not gain more heart protection and, in fact, had the same level of risk as men who never ate fatty fish or omega-3 fatty acids, the study found.

This was an unexpected finding and may be due to chance, the researchers said.

"Alternatively, these may be men in poor health who ate more fish to try to improve their ill-health, and therefore the fatty fish and fatty acids appear to be risk factors for heart failure," the study's leader, Dr. Emily Levitan, a cardiology research fellow at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston, said in a news release from the European Heart Journal, where the findings are published. "I suspect this is the most likely explanation, but we cannot be certain from our data."

SOURCE: European Heart Journal, news release, April 21, 2009