Vitamin D is felt to play an essential role in preventing bone disease. We know that Vitamin D is synthesized directly in the skin through the action of UV radiation. We do not know exactly how much vitamin D is required from our diet. Dermatologists do know that sun protection does decrease the risk of skin cancer and does not deprive us the opportunity to synthesize Vitamin D. So, what is the controversy?
Sunlight (UV exposure) does generate Vitamin D in the skin, and the levels of serum (blood) 25-hydroxyvitamin D levels are higher in seasons with more average sun exposure. However, there are no studies which can tell us how much sun exposure is necessary for an individual to achieve a certain vitamin D level, because of factors such as skin pigmentation, body surface area exposed to the sun, age, and current serum 25-hydroxyvitamin D levels.
The Institute of Medicine (IOM) committee has set its recommendations for vitamin D intake with the assumption that there should be MINIMAL contribution from sun exposure. Dietary sources should be relied upon to meet our needs.