Vitamin D Supplementation and Longer-Term Endometriosis-Associated Pain Outcomes: A Systematic Review
Keywords:
Adjunct therapy; Dysmenorrhea; Endometriosis-associated pain; Long-term effects; Pelvic pain; Vitamin D supplementation.Abstract
Endometriosis is a chronic inflammatory condition that is known to be associated with severe pelvic pain and dysmenorrhea. Vitamin D has potential anti-inflammatory and immunomodulatory effects that may influence these outcomes. This review aimed to assess the effects of vitamin D supplementation on longer-term endometriosis-associated outcomes, defined as pain assessed at six months or longer from baseline or beginning of treatment. The methodology involved searching databases such as PubMed and Scopus from October 2025 through January 2026, identifying 604 records, of which three met the inclusion criteria. Studies including women with diagnostically confirmed endometriosis, vitamin D supplementation, and reporting pain outcomes like dysmenorrhea and pelvic pain, with a follow-up of at least six months, were considered. We excluded case reports, editorials, reviews, animal studies, and in vitro studies, as well as studies involving women without diagnostically confirmed endometriosis.
Additionally, the risk of bias assessment indicates that both RCTs show some overall concerns of bias. The non-randomized study was rated as having a serious risk of bias, mainly due to participant selection, intervention classification, deviation from intended interventions, and outcome measurement. The results mainly include three studies that met the inclusion criteria, one non-RCT and two RCTs. It was observed that vitamin D showed slight improvement in pelvic pain and dysmenorrhea. The current studies are insufficient to confirm whether vitamin D can effectively improve endometriosis-associated pain outcomes. Findings across studies remain inconsistent, with substantial improvement also observed in placebo and no statistically significant between-group differences, undermining definitive conclusions. Additionally, the longer-term outcomes remain under-explored. These limitations highlight the need for well-designed trials with standardized outcome measures and a follow-up of six months or more.
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