Want a healthier heart? Try adding fish to your diet. But be careful how it’s cooked, a new study warns: baked or broiled fish will boost heart health, but fried fish is probably better left uneaten.
Using data from the long-term Women’s Health Initiative, the study tracked the diets of about 85,000 postmenopausal women for an average of 10 years. Researchers found that women who ate five or more servings of fish per week had a 30% lower risk of developing heart failure than those who ate fish less than once a month. But the benefit applied only if the fish was baked or broiled.
Fried fish showed no heart-protective effect. Women who ate even one serving of fried fish a week had a 48% higher risk of heart failure, compared with those who rarely or never ate it. The association persisted, even after researchers accounted for the women’s overall diet and medical histories.
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“Not all fish are equal, and how you prepare it really matters,” said lead author Dr. Donald Lloyd-Jones of Northwestern University Feinberg School of Medicine in a statement. “When you fry fish, you not only lose a lot of the benefits, you likely add some things related to the cooking process that are harmful.”
It’s not the first study to suggest that eating fried fish yields little health benefit. A recent survey of the dietary habits of people living in the so-called “stroke belt” of the U.S. — the region that stretches from the Carolinas to Arkansas and Louisiana, where stroke rates are among the highest in the country — found that these residents were 17% less likely than other Americans to eat the federally recommended two servings of non-fried fish per week, and 32% more likely to eat fried fish at least twice a week. They were also 20% more likely than Americans in other parts of the country to have a stroke.
Doctors have long advised their patients to eat more fish because it is so rich in omega-3 fatty acids, which are thought to reduce the risk of heart disease by lowering inflammation, blood pressure and cell damage. Although the data on the benefits of fatty acids on stroke risk are less conclusive, many of the same risk factors that promote heart disease, including high blood pressure and inflammation, can also contribute to stroke.
(More on TIME.com: Is Eating Fish Good For You — Even If It’s Fried?)
In a separate study, Lloyd-Jones and his colleagues found that some types of fish were better than others when it came to heart health. Dark, oily fish such as salmon, mackerel and bluefish — which are higher in omega-3s — were associated with a lower risk of heart failure than tuna or white fish like cod or sole. But the researchers said that omega-3s may not be the only magic ingredient in fish. Health.com reports:
Using detailed diet questionnaires, the researchers estimated the study participants’ total intake of omega-3 fatty acids (including from fish oil supplements), and found no link between omega-3s on their own and reduced rates of heart failure.
This suggests that it’s the whole fish — rather than its component parts — that provides heart protection, Lloyd-Jones says.
The study’s findings reinforce current dietary recommendations. The American Heart Association suggests eating at least two 3.5-ounce servings of fish, especially fatty fish, per week.
The new research was published in the journal Circulation: Heart Failure.