Sunshine and vitamin D.

Vitamin D is vital for bone health and its deficiency deemed as a disease of the past has re-emerged as an important health concern. Exposure of the skin to solar ultraviolet B radiation is the major source of vitamin D and only a small proportion is derived from dietary intake. We review the various factors that influence the cutaneous synthesis of vitamin D and the recommendations regarding safe sun exposure and dietary supplementation to achieve adequate vitamin D levels proposed for optimal bone health.