Effects of ambient sunlight and photoprotection on vitamin D status.

Ultraviolet B radiation exposure is responsible for the majority of natural vitamin D stores in humans. The physiologic role of vitamin D in health and disease is continually expanding, and at the same time the population that is vitamin D deficient is increasing. The environmental characteristics and personal physical traits that contribute to vitamin D3 synthesis from sun exposure are discussed, and the effects of photoprotection on vitamin D status are examined. It is concluded that sunscreen, in the manner used by the general public, does not cause vitamin D insufficiency. Implementing guidelines suggesting sun exposure duration for sufficient vitamin D3 production is limited by the complex interaction of contributory factors, and no recommendation can be made that is both safe and accurate enough for general public usage.