tl;dr: Vitamin D RCTs have refuted the magical correlations (no 30% mortality reduction), but the author argues skeptics overcorrected: trials consistently show hazard ratios slightly below 1 for cancer and all-cause mortality, and detecting modest-but-meaningful effects would require sample sizes far larger than any trial conducted. Combined with evolutionary evidence (ancestral levels ~115 nmol/L, pale skin evolving despite folate costs) and biology (vitamin D receptors throughout the body), supplementing if you have low-ish levels is probably worthwhile—even a HR of 0.96 would beat the cost of a daily pill.