New Approach to Develop Optimized Sunscreens that Enable Cutaneous Vitamin D Formation with Minimal Erythema Risk.

Sunscreens protect the skin against erythemal radiation (Eer). But at the same time they reduce the effective radiation dose (EVD) responsible for the formation of previtamin D in the skin. The paper describes a calculation method for optimizing the ratio EVD/Eer behind sunscreens e.g. with SPF 5, 15 and 30 respectively. Taking into account that a majority of people in industrialized countries suffer from a shortage in vitamin D even in summer time, the ratio Evd/Eer is a new and important criterion for the quality of sunscreens. Furthermore the exposure time tvd needed per day for forming the equivalent of the recommended amount of 2000 IU of vitamin D per day for skin type 2 is estimated when sunscreens with different filter compositions are used. In vitro experiments show a significant increase of the conversion of 7-dehydrocholesterol (7-DHC) to previtamin D when exposed to artificial solar radiation behind an experimental sunscreen optimized for previtamin D production compared to a commercial sunscreen having the same SPF.