Common misconceptions about vitamin D--implications for clinicians.

Misconceptions about vitamin D continue to grow despite publications in the past few years that have attempted to clarify risk. We present our perspective, and offer several conclusions. Calcium and vitamin D supplementation can reduce fracture risk by ∼10%. On the other hand, little evidence exists to support a threshold measure for vitamin D status (serum levels of 25-hydroxyvitamin D) above which fractures are reduced. The association of serum concentrations of 25-hydroxyvitamin D with other chronic diseases is confounded by multiple factors and conflicting outcomes that cannot be used to support a causal association. High doses of vitamin D supplements might not be completely harmless and should be avoided until additional data becomes available. Similarly, scant rationale exists for aggressive vitamin D supplementation for pregnant or lactating women. Dispelling misconceptions about vitamin D will ultimately benefit health-care providers and patients alike.