Women who eat more red meat — especially of the non-processed variety — seem to be more likely to develop endometriosis, according to a prospective study.

The study, “A prospective cohort study of meat and fish consumption and endometriosis risk,” was published in the American Journal of Obstetrics and Gynecology.

There has been increasingly more interest among researchers in identifying modifiable risk factors that contribute to the development of endometriosis — such as diet and exercise.

Diet can affect levels of certain hormones which, in turn, may have an influence on the risk of endometriosis. In particular, studies have shown that meat products can increase levels of estrogen and prostaglandin, which favor the inflammatory and proliferative characteristics of endometriosis.

However, to date, only two case-control studies have investigated the association between meat consumption and endometriosis risk, both of which produced inconsistent results.

Researchers in this study set out to determine whether higher intakes of red meat, poultry, and seafood are associated with a higher risk of endometriosis.

They assessed 81,908 participants in a prospective study that followed nurses from 1991-2013. Their dietary intake was determined using a food frequency questionnaire every four years. Statistical analysis was then used to calculate which food products were more likely to be associated with endometriosis development.

During this time period, 3,800 laparoscopically confirmed cases of endometriosis were reported.

Statistical analysis indicated that women who ate more than two servings per day of red meat had a 56% higher risk of developing endometriosis than women who consumed one serving or less of red meat a week.

This association was strongest for consumption of non-processed red meats (hamburger, beef/pork/lamb sandwich, pork, beef, and liver). In fact, women who ate two servings or more of non-processed red meat per day had a 1.57 times higher risk of developing endometriosis than those who had one serving or less a week.

Interestingly, this association was higher among women who did not have infertility, suggesting the link may be due to an influence of diet on pain symptoms.

In addition to non-processed red meat, women who ate five servings or more of processed red meat (hot dog, bacon, and sliced processed meat) per week had a 1.2 times higher risk of developing endometriosis than women who had less than one serving a month.

Statistical analysis shows that eating poultry, fish, shellfish, and eggs were unrelated to endometriosis risk.

“Our prospective analysis among premenopausal US nurses suggests that red meat consumption may be an important modifiable risk factor for endometriosis, particularly among women with endometriosis who had not reported infertility and thus were more likely to present with pain symptoms,” the authors concluded.