Women who eat lots of tuna, salmon and other foods rich in essential omega-3 oils might be less likely to develop endometriosis than those whose diets are loaded with trans fats, U.S. researchers said on Tuesday.

Endometriosis, which has no cure, can cause infertility. In endometriosis, pieces of the uterine lining grow outside the womb, sometimes sticking to other organs.

The type of fat in a woman’s diet, rather than the total amount, may be a risk factor for endometriosis, an often debilitating and painful condition, researchers said in a study published online in the journal Human Reproduction.

The study of more than 70,000 American nurses found that women who ate the most omega-3 fatty acids were 22 percent less likely to be diagnosed with endometriosis than women who ate the least.

Women who ate the most trans fats had a 48 percent increased risk of the condition compared with those who ate the least, the study found.

Trans fats are formed when liquid fats are hardened to make something more resembling butter or lard. And like the saturated fat in lard, they raise the likelihood of heart disease.

This study suggests they can also affect endometriosis risk.

“We know that trans fats increase the body’s level of many inflammatory markers and these are inflammatory factors that have been shown to be associated with establishment of endometriosis and progression,” Dr. Stacey Missmer of Brigham and Women’s Hospital and Harvard Medical School in Boston, who led the study said in a telephone interview.

The risk is likely increased because of a chronic inflammatory response to the trans fat, Missmer said.

She stressed that this is the first study to show such an association but said more research is needed to confirm the results. Still, Missmer said study provides more evidence of the benefits of healthy eating habits.

“Many women have been searching for something they can actually do for themselves, or their daughters to reduce the risk of developing the disease, and these findings suggest that dietary changes may be something they can do,” Missmer said in a statement.

The researchers looked at the diets of 70,709 women followed for 12 years in the U.S. Nurses Health Study. The types of fats the nurses ate were broken down into five categories and the researchers looked to see who later developed endometriosis.

Over the course of the study, 1,199 women did.

Most of the omega-3 fatty acids eaten by the nurses came from full-fat salad dressing, followed by fatty fish like tuna, salmon and mackerel. Walnuts and flaxseeds are also considered good sources.

Omega-3 fatty acids, considered essential for good health, can lower heart disease risk.

The major sources of trans fats in the study were fried foods from restaurants, margarine and crackers.

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By JoAnne Allen

WASHINGTON (Reuters)