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Evidence-Based Supplement Research
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Vitamin D and Reduced C-Reactive Protein Levels

Research synthesisModerate evidenceModerate effect7 studies · 4 beneficial · 3 neutral · 0 harmful

Across 7 studies (including 4 meta-analyses), 4 reported beneficial moderate-sized effects of vitamin D supplementation on reducing C-reactive protein levels, particularly in clinical populations such as overweight/obese individuals, patients with diabetes or prediabetes, and those with extrapulmonary tuberculosis. Three studies found no significant effect in psoriasis, overweight children, and older adults with vitamin D deficiency. The median study duration was approximately 4 months.

  • Studied populations: overweight/obese adults, patients with diabetes or prediabetes, and patients with extrapulmonary tuberculosis

Caveats: While the majority of studies show benefit, three high-quality studies (including a meta-analysis on psoriasis) found no significant effect, suggesting the impact may be population-specific. Most studies did not specify the form of vitamin D (D2 vs D3), and dosing regimens varied widely. Benefit may be limited to individuals with underlying inflammation or deficiency, but baseline vitamin D status was not consistently reported across all studies.

Generated Jun 11, 2026
Doses used in studies
  • IU/day: 1,000 (median 1,000, IQR 1,000–1,000) — 2 studies
Time to effect
Median: 3.9 months · IQR 2.9 months–5 months · Range 8 weeks–6 months — Reported in 2 of 7 studies
Safety in these studies
7 of 7 papers
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