Vitamin D and Prevention of Cancer — Ready for Prime Time? — NEJM

"Despite biologic plausibility and widespread enthusiasm, the IOM committee found that the evidence that vitamin D reduces cancer incidence and related mortality was inconsistent and inconclusive as to causality.
New trials assessing moderate-to-high-dose vitamin D supplementation for cancer prevention are in progress and should provide additional information within 5 to 6 years.
Although future research may demonstrate clear benefits of vitamin D related to cancer and other nonskeletal health outcomes, and possibly support higher intake requirements, the existing evidence falls short."