Vitamin D: newly discovered actions require reconsideration of physiologic requirements.

Vitamin D is not just for preventing rickets and osteomalacia. Recent findings in animal experiments, epidemiologic studies and clinical trials indicate that adequate vitamin D levels are important for cancer prevention, controlling hormone levels and regulating the immune response. Although 25 hydroxyvitamin D (25OHD) levels >10 ng/ml can prevent rickets and osteomalacia, these levels are not sufficient to provide these more recently discovered clinical benefits. Rather, levels of 25OHD >30 ng/ml are generally recommended. Determining optimal levels of 25OHD and the amount of vitamin D supplementation required to achieve those levels for the numerous actions of vitamin D will only be established with additional trials. In this review, these newer applications are summarized and therapeutic considerations are provided.