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Evidence-Based Supplement Research
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Vitamin D and Reduced Interleukin-6 Levels

Research synthesisModerate evidenceMixed effect size8 studies · 5 beneficial · 3 neutral · 0 harmful

Across 8 studies, 5 reported beneficial effects (4 statistically significant) and 3 reported neutral effects, with no harmful findings. The predominant effect size is small to moderate, with the most robust evidence coming from RCTs showing moderate effects in clinical populations (e.g., colorectal cancer patients, overweight/obese adults). Doses ranged from 200 IU/day to personalized loading doses, and the median study duration was 56 days, indicating effects typically observed at 8–12 weeks.

  • Effective dose range: 200–5000 IU/day (most consistent evidence near 2000 IU/day or personalized loading doses)
  • Studied populations: clinical populations (colorectal cancer patients, overweight/obese adults with low-grade inflammation, moderate to severe traumatic brain injury patients)

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). Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Two systematic reviews showed neutral or small effects, tempering confidence. Studies varied widely in dose, duration, and population, limiting generalizability.

Generated Jun 12, 2026
Doses used in studies
  • IU/day: 200–5,000 (median 1,000, IQR 600–3,000) — 3 studies
  • IU single-dose: 300,000 (median 300,000, IQR 300,000–300,000) — 1 study
Time to effect
Median: 8 weeks · IQR 8 weeks–10 weeks · Range 8 weeks–2.8 months — Reported in 3 of 8 studies
Safety in these studies
8 of 8 papers
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