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New guidelines from the American Heart Association published today in the journal Circulation cement the importance of eating fish to help protect your heart.

The panel of experts who produced the AHA’s new scientific advisory on fish consumption reviewed the research that has emerged in the decade and a half since the AHA’s last issued recommendations for eating fish in 2002.

 “We looked at several more cardiovascular disease-related endpoints [related to seafood consumption], including congestive heart failure, stroke, and hypertension,” says Eric B. Rimm, Sc.D., chair of the AHA’s writing group and professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health in Boston. “Also, there is substantially more evidence now pointing to seafood intake and lower risk of coronary heart disease and sudden cardiac death—especially when the seafood replaces less healthy main dishes such as beef or pork.”

In the end, the panel found no reason to change the AHA’s current recommendations for eating fish: Have two servings of nonfried fish—especially fatty fish—per week. A serving is 3½ ounces of cooked fish or ¾ cup of flaked fish.

“The more recent data continues to support the benefits of consuming fish, preferably in place of foods high in saturated fat and low in unsaturated fat,” says Alice H. Lichtenstein, D.Sc., director and senior scientist at the Cardiovascular Nutrition Laboratory at Tufts University and a coauthor of the AHA advisory.

Why Fish Is so Good for You

It’s the omega-3 fatty acids, which are plentiful in many types of seafood, that probably confer most of the heart benefits of eating fish. “Omega-3s are important for cell-to-cell signaling in heart muscle and for cells within the lining of the arteries,” Rimm says. They reduce inflammation, help prevent heart rhythm abnormalities, improve the flexibility of arteries, and help lower cholesterol.

The advisory authors analyzed evidence from a multitude of observational studies and randomized controlled trials, looking at the beneficial effects of omega-3s on cardiovascular health. Some of the key findings include:

• 50 percent lower risk of sudden cardiac death in those who ate one fatty fish meal a week compared with a diet containing little or no seafood.

• People who ate one serving of fish a week had a 14 percent lower risk of ischemic stroke (the type caused by a blood clot in the brain) than those who ate little or no fish.

• Those who consumed seafood four or more times a week had a 22 percent lower risk of coronary heart disease overall vs. those who ate it less than once a month.

Fish vs. Fish Oil Pills

If you don’t like seafood, you may wonder if you can reap the same benefits by simply popping a pill.

The AHA released a scientific advisory on this topic last year, recommending omega-3 supplements to people who’ve had a heart attack or have been diagnosed with heart failure.

But for everyone else, the authors concluded that the current evidence showed no benefit of taking fish oil supplements in preventing heart attack, stroke, or heart failure.

“The benefits of fish are likely due in part to the omega-3 fatty acid content, but may also be due to choosing fish in place of high-saturated fat foods like steak,” Lichtenstein says. “Just taking a supplement isn’t the same as making healthier choices in your diet.” 

Is More Fish Better?

It’s possible that going beyond the recommended two servings a week could provide additional health benefits. But hard evidence is lacking. “There just aren’t a lot of studies that included consumption at higher levels,” Rimm says.

Based on the available evidence, the researchers concluded that much of the benefit comes from moving from very little or no fish in the diet to eating fish once or twice a week. “However, if fish is consumed four or more times a week as a substitution for other less healthy foods, then I do think that more is better,” Rimm says.

Choose Low-Mercury Fish

One downside of increasing the amount of fish you eat is potential exposure to mercury, a toxin that can affect brain development in fetuses and young children, and in excess may affect the health of adults as well.

At the same time, though, women of childbearing age (especially those who are pregnant or breastfeeding) and children are encouraged to eat fish to get the omega-3s that support growing brains, and everyone should be eating fish to boost their heart health.

“It’s healthy to eat fish, and you can even eat a lot of fish. You just need to pay attention to which fish are high or low in mercury,” says Jean Halloran, director of food policy initiatives at Consumers Union, the advocacy division of Consumer Reports. “There are acute neurological risks of too much mercury, even for adults—from mental fuzziness to tremors and loss of balance.”

The AHA urges people to choose fatty fish highest in omega-3s for their two servings a week. Its list includes salmon, mackerel, herring, lake trout, sardines, and albacore tuna.

But some of those recommendations are at odds with the Food and Drug Administration’s guidelines for women of childbearing age and children. The FDA lists albacore tuna as a “once a week choice.” And while Atlantic mackerel is low in mercury and okay to eat two or more times a week, King mackerel is a high mercury fish that the FDA recommends avoiding.

The authors of the AHA advisory did not find that mercury had any adverse effects on cardiovascular disease and concluded that the heart-health benefits of eating fish twice a week outweigh any risks, especially if you consume a variety of seafood. Rimm notes, however, that they did not look at pregnant women or children in their review of the research.

Consumer Reports recommends getting your omega-3s from low-mercury fish. Fortunately, some of these are rich sources of omega-3s: Atlantic mackerel, sardines, salmon (including canned), and trout. “Although other low-mercury fish, such as catfish, flatfish and sole, shrimp, and tilapia don’t supply as much omega-3s, they do contain some,” Halloran says.

As for tuna—the most popular type of seafood next to shrimp—Halloran notes that previous Consumer Reports analyses of mercury levels in tuna suggest that pregnant women shouldn’t eat it at all. Everyone else should opt for chunk light, which has one-third of the mercury of albacore and about one-fifth of the mercury in sushi tuna (such as bigeye), and not make tuna the only type of seafood they eat.

Sally Wadyka is a freelance writer who contributes to Consumer Reports, Real Simple, Martha Stewart Living, Yoga Journal, and the Food Network on topics such as health, nutrition, and wellness.