Eating baked or broiled fish at least five times a week can lower the chance of heart failure by 30 percent, according to a new study. But not all fish preparations are alike eating fried fish just once a week increases the risk of heart failure by 48 percent.

The study shows that not all fish are equal, and the way it is cooked makes a difference as to its effect on the body, said study researcher Dr. Donald Lloyd-Jones, associate professor and chair of the department of preventive medicine at Northwestern University Feinberg School of Medicine in Chicago.

Researchers also found that consumption of dark fish such as salmon, mackerel and bluefish reduces the risk of heart failure more than tuna and whitefish such as sole, snapper and cod, Jones said.

"The darker types of fish tend to be higher in omega-3 fatty acids, but are also higher in other potentially beneficial nutrients," Lloyd-Jones told MyHealthNewsDaily.

The study shows that it is important to eat fish as part of an overall healthy diet, and not just rely on supplements and pills to provide the same benefits, he said.

The study was published today (May 24) in the journal Circulation: Heart Failure.

Fried versus baked

Lloyd-Jones and his colleagues looked at self-reported dietary data from 84,493 postmenopausal women who were part of the nationwide Women's Health Initiative Observational Study.

Researchers divided the women into two groups: a group that regularly ate broiled or baked fish, and a group that regularly ate fried fish. The broiled and baked fish group mainly consumed broiled or baked dark fish, broiled or baked whitefish, canned tuna, tuna salad, tuna casserole and shellfish . The fried fish group mainly ate fried fish, fish sandwiches and fried shellfish.

During an average of 10 years of follow-up, there were 1,858 cases of heart failure across both groups, according to the study.

The women who ate the most broiled or baked fish were 30 percent less likely to develop heart failure over the 10-year study period than the women who ate broiled or baked fish less than once a month, the study said.

Meanwhile, women who ate fried fish just once a week had a 48 percent increased risk of heart failure, according to the study.

Researchers found that people who ate broiled and baked fish tended to be healthier, younger, fitter, more educated and less likely to smoke, have diabetes, high blood pressure or heart disease compared with the people who regularly ate fried fish. Those who ate broiled and baked fish were also more likely to eat more fruits and vegetables and less saturated fats than people who regularly ate fried fish, the study said.

A surrogate for lifestyle

The omega-3 fatty acids in fish have been shown in previous research to decrease inflammation and improve blood pressure and blood vessel function, Lloyd-Jones said.

Past research has suggested that frying fish increases the amount of trans fatty acids in the foods, which is known to increase heart disease risk. However, researchers did not find a link between trans fatty acids and heart failure risk in this study, he said.

A study published last year in the journal Neurology also showed that fried fish could be a contributor to America's "stroke belt" a string of Southern states where residents have a 20 percent higher risk of dying from stroke than people in other parts of the country. These people are also 30 percent more likely to regularly eat fried fish than people in other parts of the country.

The type of fish that people consume is likely a surrogate "for other aspects of healthier [and] less healthy lifestyles," Lloyd-Jones said.

"The take-home, I think, remains that eating baked or broiled fish more frequently as part of an overall healthy dietary pattern is associated with lower risks for heart failure, and other demonstrated health benefits as well," he said.

Pass it on: Eating baked and broiled fish lowers the risk of heart failure, but eating fried fish can actually raise the risk.

Follow MyHealthNewsDaily staff writer Amanda Chan on Twitter @AmandaLChan.