There’s more good news about eating fish and healthy hearts.

And there are some big differences between eating farmed salmon and wild, and the way it’s prepared really matters. reports on the Journal of the American Medical Association, which pooled data from four international studies of nearly 200,000 people. The goal was to make the connection between eating fish rich in omega-3 fatty acids and the risk of getting and dying from heart disease.

For those who already have a bad heart, JAMA concluded that eating two to four, 4 ounce servings of fish a week reduces their risk of dying by a whopping 36%.

They  touted salmon as delivering some of the biggest doses of omega-3’s along with protein, selenium, B12 and vitamin D.

And they noted some big differences between farmed and wild salmon. A small wild salmon fillet  has 131 fewer calories and half the fat content as the same amount of farmed fish. Farmed salmon can have slightly more omega-3s, but it also has 20% more saturated fat.

The JAMA also mentioned higher levels of “persistent organic pollutants” that  are resistant to biodegrading. Levels of polychlorinated biphenyls or PCBs, for example, are five to 10 times higher in farmed salmon than in wild caught.

The adverse effects of PCBs were so widespread the chemical was banned in the U.S. in 1979, but most farmed fish comes into the U.S. from other countries that don’t have the same restrictions. The study also referred to the wide use of antibiotics in most farmed fish growing operations.

The Center for Disease Control said there are heart-healthy benefits from other fish besides salmon, notably sardines, anchovies, herring, trout, flounder and canned tuna.

How the fish is cooked really matters. A weekly diet of fried fish increases heart attack by 17% as it cancels out the healthy fat benefits of the fish. Researchers recommend broiling, steaming, sauteeing, poaching or stewing fish and making it a permanent part of a heart-smart diet.

It’s more proof that you are what you eat.