The inflammation-fighting effects of omega-3 fatty acids may be the key behind fish’s heart-healthy benefits, according to a new study.

Researchers found inflammation markers, such as C-reactive protein and others, were up to a third lower in people who ate at least 10 ounces of fish per week compared with those didn’t eat fish. The more fish the people ate, especially fish rich in omega-3 fatty acids such as salmon, mackerel, and tuna, the lower their level of markers of inflammation in the bloodstream.

Omega-3 fatty acids are a type of unsaturated fat that has been shown to reduce the rates of heart disease and death from heart disease. The mechanism behind this action is unknown but studies show that they reduce inflammation.

Inflammation within blood vessels plays a key role in the development of atherosclerosis -- a risk for heart disease and stroke.

Therefore, researchers say the anti-inflammatory effects of the omega-3 fatty acids in fish found in this study may explain why fish is healthy for the heart.

"For the general public it could be suggested that consuming fish one or two times per week could lead to these beneficial effects found in our study,” says researcher Demosthenes B. Panagiotakos, PhD, of Harokopio University in Athens, in a news release. “The general recommendation is to avoid frying the fish.”

Read WebMD's "What You Need to Know About Eating Fish"

Fish Fight Inflammation to Keep Heart Healthy

In the study, which appears in the Journal of the American College of Cardiology, researchers compared fish consumption and blood inflammation markers in a group of about 3,000 men and women in the Attica region of Greece.

None of the participants had a history of heart disease, and nine out of 10 said they ate fish at least once a month.

The results showed that compared with those who said they didn’t eat fish, those who ate at least 10.5 ounces of fish per week had 33 percent lower C-reactive protein and 33 percent lower tumor necrosis factor-alpha (another indicator of inflammation) levels as well as much lower levels of other signs of inflammation. People who ate about 5 to 10 ounces of fish per week also had lower levels of inflammation in the bloodstream.

"We revealed that not only the fish portion, but also the amount of omega-3 fatty acids seems to play a role in the reduction of inflammatory markers levels,” says researcher Antonis Zampelas, PhD, of Harokopio University in Athens, in the release.

Researchers say an average daily dose of omega-3 fatty acids of about 0.6 grams, regardless of the fish source, appeared to be the optimal level to achieve the inflammation-fighting benefits and lower the risk of heart disease.

Three ounces of the following fish provide 1 gram of the omega-3 fatty acids known as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Herring, Pacific, 1.5 ounces cooked Salmon, chinook, 2 ounces cooked Salmon, Atlantic, 2.5 ounces cooked Oysters, Pacific, 2.5 ounces cooked Trout, rainbow, 3.5 ounces cooked Tuna, white, packed in water 4 ounces cooked

The American Heart Association recommends eating fish (particularly fatty fish) at least twice a week. Fatty fish high in omega-3 fatty acids include mackerel, lake trout, herring, sardines, albacore tuna, and salmon.

Read WebMD's "Mediterranean Diet Linked to Longer Life"

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Zampelas, A. Journal of the American College of Cardiology, July 5, 2005; vol 46: pp 121-124. News release, American College of Cardiology. American Heart Association. Linus Pauling Institute.