Supplementation with vitamin D or ω-3 fatty acids in adolescent girls and young women with endometriosis (SAGE): a double-blind, randomized, placebo-controlled trial.

Double-blind, randomized, placebo-controlled trial conducted at Boston Children's Hospital in the United States. Adolescent girls and young women aged 12 to 25 years with surgically confirmed endometriosis and pelvic pain were enrolled between October 2014 and November 2015.

Participants received one of two oral supplements for 6 months: vitamin D3 2000 IU daily (cholecalciferol) or fish oil 1000 mg daily providing 720 mg omega-3 fatty acids, including 488 mg EPA and 178 mg DHA. Both active arms were compared with placebo while participants continued standard-of-care treatment.

Overall, vitamin D and omega-3 supplementation did not show clear benefit over placebo for endometriosis-related pain or quality-of-life outcomes. Vitamin D produced within-arm improvement in worst monthly pain from 7.0 to 5.5 and reduced catastrophic thinking from 25.3 to 20.8, but the clinically meaningful pain response was not greater than placebo (OR 1.9, 0.5 to 6.5). Fish oil showed a smaller pain change from 5.9 to 5.2, with no significant advantage over placebo (OR 0.9, 0.2 to 3.7). Across all arms, pain and quality-of-life measures improved similarly, suggesting a strong placebo or trial-participation effect.

The trial was conducted at a single center and the active-arm data suggest limited power, with wide confidence intervals around treatment effects. Follow-up was only 6 months, adverse events were not described, and the similar improvement across placebo and active arms limits causal inference about supplement benefit.