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Evidence-Based Supplement Research
Evidence-Based Supplement Research
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Vitamin D and Improved Physical Function

Research synthesisLow evidenceMixed effect size3 studies · 2 beneficial · 1 neutral · 0 harmful

Across 3 studies, 2 reported beneficial effects on physical function (one with moderate effect size, one with large effect size), while 1 large RCT found a neutral effect. The evidence suggests a possible benefit, but the largest and longest study (3 years, 2000 IU/day) showed no improvement, and the median study duration was 576 days. Doses ranged from 200 IU to 2000 IU/day, and most studied populations were clinical or elderly.

  • Studied populations: Adults with overweight/obesity and low-grade inflammation; older adults with or without sarcopenia or frailty; generally healthy and active older adults

Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. The largest and highest-quality trial (DO-HEALTH, n=2157, 3 years) found no benefit, contradicting smaller positive studies, which raises uncertainty. The beneficial meta-analysis included only 18 participants, limiting reliability.

Generated Jul 12, 2026
Doses used in studies
  • IU/day: 200–2,000 (median 1,100, IQR 650–1,550) — 2 studies
Time to effect
Median: 19.2 months · IQR 10.5 months–27.8 months · Range 8 weeks–36.5 months — Reported in 2 of 3 studies
3 of 3 papers
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