Research synthesisLow evidenceMixed effect size3 studies · 3 beneficial · 0 neutral · 0 harmful
Across 3 studies, all reported beneficial effects of vitamin D on reducing oxidative stress, with effect sizes ranging from small to large. One high-quality clinical trial in multiple sclerosis patients found large reductions using 50,000 IU/week for 8 weeks (median study duration 56 days). Effects were also observed in healthy adults, though one study used a multi-ingredient probiotic blend, limiting attribution to vitamin D alone.
- Studied populations: multiple sclerosis patients, generally healthy adults
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Evidence base is small (only 3 studies) — conclusions should be considered preliminary. One of the clinical trials tested vitamin D in combination with a probiotic, not as a standalone intervention. Only one study reported a specific dose and duration, limiting dose-response conclusions.
Generated Jul 12, 2026