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Evidence-Based Supplement Research
Evidence-Based Supplement Research
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Vitamin D and Reduced Body Mass Index

Research synthesisLow evidenceSmall effect9 studies · 1 beneficial · 8 neutral · 0 harmful

Across 9 studies, 1 reported a beneficial moderate-sized effect on reduced BMI, while 8 reported neutral small effects. The predominant effect direction is neutral with a small effect size. Most studies were in clinical populations (e.g., women with PCOS, people with depression, obese children) and doses varied or were not specified; median study duration was 84 days.

  • Studied populations: Clinical populations including women with PCOS, people living with HIV on HAART, individuals with depression, obese/overweight children and adolescents, and hypertensive obese OSA patients.

Caveats: Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. The single beneficial finding was from a low-quality review with a moderate effect size; most higher-quality evidence shows no effect. Evidence base is small (only 9 studies) — conclusions should be considered preliminary.

Generated Jun 12, 2026
Doses used in studies
  • IU/day: 5,000 (median 5,000, IQR 5,000–5,000) — 1 study
Time to effect
Median: 2.8 months · IQR 10 weeks–3.3 months · Range 8 weeks–3.7 months — Reported in 2 of 9 studies
Safety in these studies
9 of 9 papers
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