Endometriosis risk reduced with modest intake of soy products

New research suggests that incorporating even modest amounts of soy into the diet may provide a protective benefit against endometriosis in women.

Researchers looked at 82,084 premenopausal participants ages 27–44 years at baseline from the Nurses’ Health Study II. Soy and isoflavone intakes were evaluated every 4 years using a Food Frequency Questionnaire.

The main outcome was self-reported laparoscopically confirmed endometriosis. Cox proportional hazard models and restricted cubic splines were used in the analyses.

A total of 3,829 incident cases of laparoscopically confirmed endometriosis were documented over 1,038,888 person-years of follow-up, translating to an incidence rate of 369 per 100,000 person-years. One additional serving of soy per week was associated with an 8-percent lower risk of laparoscopically confirmed endometriosis (hazard ratio [HR], 0.92, 95 percent confidence interval [CI], 0.87–0.98).

The protective association between soy intake and laparoscopically confirmed endometriosis was observed among participants without a concurrent report of infertility (HR, 0.92, 95 percent CI, 0.86–0.99) but not among those with a concurrent infertility diagnosis (HR, 0.97, 95 percent CI, 0.83–1.13).

Intake of isoflavones had an inverse association with laparoscopically confirmed endometriosis, with the association being approximately linear up until an intake of 4 mg/d (approximately 95th percentile of intake) and plateauing thereafter.