Glycemic Index, Glycemic Load, Fiber, and Gluten Intake and Risk of Laparoscopically Confirmed Endometriosis in Premenopausal Women

Background: The etiology of endometriosis is not well understood. Limited evidence suggests that dietary factors influence risk, but prospective data related to carbohydrate, fiber, and gluten consumption are scarce. Despite this, recommendations concerning fiber, gluten intake, and endometriosis are pervasive in the lay literature. Objectives: We aimed to investigate the associations of carbohydrate quality [glycemic index (GI) and glycemic load (GL)], fiber intake (total, legume, vegetable, cruciferous vegetable, fruit, cereal), and gluten intake with incident laparoscopically confirmed endometriosis. Methods: This was a prospective cohort study using data collected from 81,961 premenopausal women in the Nurses’ Health Study II (mean age = 36 y in 1991). Diet was assessed with a validated FFQ every 4 y. Cox proportional hazards models were used to calculate rate ratios (RRs) and 95% CIs. Results: A total of 3810 incident cases of laparoscopically confirmed endometriosis were reported over 24 y of follow-up. Women in the highest quintile of GI had 12% (95% CI: 1.01, 1.23; P_trend = 0.03) higher risk of endometriosis diagnosis than those in the lowest quintile. Total vegetable and cruciferous vegetable fiber intakes were also associated with higher risk (highest compared with lowest quintile RR: 1.13; 95% CI: 1.02, 1.24; P_trend = 0.004 and RR: 1.17; 95% CI: 1.06, 1.29; P_trend = 0.02, respectively). Higher intake of fruit fiber was associated with lower risk of endometriosis but the association was not significant after adjusting for the Alternative Healthy Eating Index. Gluten intake was also associated with lower risk (highest compared with lowest quintile RR: 0.91; 95% CI: 0.80, 1.02; P_trend = 0.01), but these results were not consistent in direction nor statistical significance across sensitivity analyses. No association was observed for GL or total, legume, or cereal fiber intake. Conclusions: Our findings suggest that carbohydrate quality and specific types of fiber—total vegetable and cruciferous vegetable fiber—are associated with endometriosis diagnosis in premenopausal women. These results also indicate it is unlikely that gluten intake is a strong factor in the etiology or symptomatology of endometriosis.