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Omega-3 fish oil supplements may slightly lower the risk of dying after heart failure or a recent heart attack, but they don’t prevent heart disease, says an issued Monday by the ÃÛÑ¿´«Ã½.

About 18.8 million adults in the United States take omega-3 fish oil supplements, according to a 2012 federal survey. The supplements contain EPA and DHA, two types of essential omega-3 fatty acids.

Controversy has surrounded the heart benefits of fish oil supplements in the 15 years since the AHA first advised people that fish oil could help prevent further heart disease. Conflicting research results have fueled the debate, said Penny Kris-Etherton, Ph.D., R.D., a nutrition professor at Penn State University who helped write the advisory.

“In 2002, the evidence was clear that there were benefits, especially for secondary prevention,” she said. “As the years went on, there were a lot of studies that didn’t show benefits. The research got very muddled. Some of the studies didn’t enroll enough people or didn’t last long enough.”

Robert Eckel, M.D., an endocrinologist and professor of medicine at the University of Colorado in Aurora, said he remains “underwhelmed” by the current clinical trials.

“In the present environment of evidence-based risk reduction, I don’t think the data really indicate that fish oil supplementation is needed under most  circumstances. However, in patients who take them, there is little, if any, risk,” said Eckel, a past AHA president who was not involved in writing the advisory. Kris-Etherton hopes the advisory will clear public confusion over omega-3 fish oil supplements. There might be some benefit in taking fish oil supplements for certain patients, but not for everybody, she said.

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Omega-3 fish oil supplements do not prevent a second heart attack, but taking about a gram a day could reduce deaths from coronary heart disease and sudden cardiac death by about 10 percent.

New to Monday’s advisory is that heart failure patients may also benefit from fish oil supplements. With heart failure, the heart struggles to pump enough blood to the body.

“Heart failure is a mixed bag,” Kris-Etherton said. “It’s not clear that every single heart failure patient is going to benefit. They’re not going to be hurt or harmed, but there may be a benefit.”

What can be said more definitively is that there’s no good evidence that the supplements can prevent coronary heart disease, heart failure or stroke, according to the advisory.

But even for people with coronary heart disease, newer and better treatments introduced in recent decades have affected studies of fish oil supplements, which before 2002 showed stronger benefits than studies conducted more recently.

For example, more patients now take cholesterol-lowering statin drugs, blood pressure medications and other drugs before and after a heart attack, Kris-Etherton said. New studies are dealing with an entirely different patient population, she said.

The supplement debate aside, eating fish such as salmon and tuna remains the best way to get enough omega-3s, experts said. Other foods that provide omega-3s include crab, mussels, flaxseed, chia seeds and canola oil.

“People are not getting enough omega-3 fatty acids,” Kris-Etherton said. “Of course, people should eat fish first, but if they can’t meet those recommendations with fish, fortified foods or supplements are OK.”

In 2012, Americans spent $12 billion overall on natural supplements, including over-the-counter fish oil supplements. Although Medicare does not cover over-the-counter supplements, it does cover prescription omega-3 fish oil pills.

Eckel said he doesn’t prescribe fish oil supplements to people who have had coronary events, and the new science advisory won’t change that. “It’s reasonable, but reasonable isn’t a solid take-home message that you should do it,” he said.