Research Synthesis: Vitamin D Supplementation Effects — full paper

Researka accepted publication: c1cbca14-3224-46cc-bd1f-bc4a92a69d25 Source submission: e14a0981-29f2-4f2d-b5b6-b4fd8f4a8ec1 Evidence-honesty note: 58/62 retained sources are indirect, review-level, adjacent, or mechanistic and are used only to bound interpretation. The conclusion therefore does not support broad causal, clinical, or policy claims. Vitamin D supplementation is among the most widely prescribed interventions worldwide, yet its clinical benefits beyond correcting deficiency remain contentious across cardiometabolic, musculoskeletal, immune, and longevity outcomes. This synthesis applies a structured, AI-assisted evidence appraisal with documented audit trails to systematically evaluate effect directions and statistical signals across 62 curated reference papers spanning randomized trials, observational cohorts, and meta-analyses. For immune and inflammatory markers, vitamin D supplementation in women with PCOS significantly reduced inflammatory biomarkers (P < 0.001) (Akbari 2018), yet a separate meta-analysis of obese or overweight populations reported mixed findings on co-supplementation with magnesium (Deng 2025). Overall, the evidence supports that vitamin D supplementation reliably raises serum 25(OH)D and may offer modest mortality or inflammatory benefits in specific clinical contexts, but effects on cardiometabolic hard endpoints, musculoskeletal function, and frailty prevention remain insufficiently suggested by current human RCTs.