THURSDAY, May 17, 2018 (HealthDay News) -- There is more reason than ever for people to make fish a bigger part of their diets, according to the American Heart Association.

The heart group has long recommended that people eat fish -- preferably fatty varieties -- once or twice a week. Now it is reaffirming that advice based on additional evidence that fish helps ward off heart disease.

Specifically, adults should strive for two 3.5-ounce servings of fish each week, the American Heart Association (AHA) said. The best choices are oily fish with large doses of omega-3 fatty acids. The options include salmon, albacore tuna, mackerel, lake trout, herring and sardines.

Whatever you choose, just don't fry it, the group warned.

That's because studies have found that fried-fish lovers have increased rates of heart failure.

The main omega-3 fatty acids in fish are EPA and DHA, said Sonya Angelone, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics.

EPA has anti-inflammatory effects that might help counter the hardening and narrowing of arteries that can lead to a heart attack, Angelone said.

Beyond that, she said, omega-3 fats may also make the blood less prone to clotting, while high doses can help lower triglycerides -- a type of blood fat.

Oily fish is not the only source of omega-3, said Angelone, who was not involved in the AHA recommendations.

"Chia seeds, flaxseeds and walnuts are good sources of alpha linolenic acid (ALA), which is a precursor to EPA -- which is then converted to DHA," Angelone said.

The problem, she added, is that only a small amount of that ALA is converted. And a persons' gene variants help determine that conversion.

In contrast, the heart association noted, 4 ounces of salmon each week would provide adults with the recommended daily intake of omega-3 -- which is around 250 milligrams.

The latest heart association advice does not differ from its previous recommendations, issued in 2002. But there is now much more evidence to back it up.

Eric Rimm, a professor at the Harvard School of Public Health, is the lead author of the AHA report, published May 17 in Circulation.

"Scientific studies have further established the beneficial effects of eating seafood rich in omega-3 fatty acids, especially when it replaces less healthy foods, such as meats that are high in artery-clogging saturated fat," Rimm said in an AHA news release.

A number of large studies have found that people who eat fish at least once a week have moderately lower risks of heart attack, stroke, heart failure and sudden cardiac death, according to the new report.

Across two large U.S. studies, replacing just 3 percent of protein calories from processed meat with protein from seafood was tied to a 31 percent reduction in the risk of dying from heart complications or stroke.

So it seems key to replace red or processed meat -- or other less-than-healthy fare -- with fish, the heart association advised.

Except, maybe, if that fish is fried. Two studies involving more than 90,000 Americans found that people who ate fried fish at least once a week were up to 48 percent more likely to develop heart failure than those who rarely fried their seafood.

Fish may even benefit people who've already suffered heart trouble, the heart association said. A study of heart attack survivors found that those who were told to eat fish twice a week were 27 percent less likely to die over the next two years, versus those given standard care only.

Seafood does contain mercury, the AHA pointed out. And pregnant women and young children should avoid certain large fish that are high in mercury -- such as shark, swordfish and king mackerel.

But for most adults, the benefits of eating fish outweigh any potential harms associated with mercury, Rimm's team said.

If you don't like fish, are fish oil supplements a good substitute? No, according to the AHA. In a previous report, the group said supplements are not recommended for preventing heart disease, due to a lack of evidence that they work.

More information

The U.S. National Institutes of Health has more on omega-3 fatty acids.