Vitamin D supplementation may reduce disease activity in SLE: a systematic review and meta-analysis

BACKGROUND: Systemic lupus erythematosus (SLE) is a complex autoimmune disease frequently associated with vitamin D insufficiency. Vitamin D supplementation has been proposed as a potential adjunctive therapeutic strategy for SLE. OBJECTIVE: To evaluate the effects of vitamin D supplementation on disease activity and related clinical outcomes in patients with SLE. METHODS: A systematic search of PubMed, Web of Science, Embase, Cochrane Library, CNKI, and Wanfang Data was conducted from inception to March 2025. Randomized controlled trials (RCTs) were included. Data extraction and statistical analyses were performed using Review Manager 5.3 and Stata/MP 16.0. Risk of bias was assessed using the Cochrane Collaboration tool. RESULTS: 10 RCTs involving 847 participants were included. Vitamin D supplementation significantly improved serum 25(OH)D status (SMD = 3.46, p < 0.001) and reduced disease activity in SLE (SMD = -0.54, p < 0.001). Significant improvements were also observed in complement component C3 (MD = 14.49, p = 0.03) and C4 (SMD = 2.08, p = 0.04). No significant effects were found for erythrocyte sedimentation rate (ESR) (MD = -10.19, p = 0.24) or fatigue severity (SMD = -1.77, p = 0.07). Anti-dsDNA antibody levels showed no significant change (MD = 7.78, p = 0.82), while positivity rates were significantly improved (RR = 5.44, p = 0.001). CONCLUSION: Vitamin D supplementation may reduce disease activity and improve complement levels in SLE, but evidence for other outcomes remains inconsistent, warranting further high-quality trials.