Photoprotection and vitamin D status.

The adverse effects of solar ultraviolet radiation on the skin are well documented, especially in fair-skinned people. These can be ameliorated by photoprotection strategies advocated by many public health bodies and typically include sun avoidance, sunscreen use and clothing. The UVB waveband which is the main cause of all adverse effects investigated in the laboratory to date is also the waveband for vitamin D photosynthesis which is the only established benefit of solar exposure. This is especially important because solar UVB is the main source of vitamin D for most people. There is increasing evidence that vitamin D plays a much greater role in human health than was previously thought. This has given rise to concerns that photoprotection, especially sunscreen use, could adversely affect vitamin D status and human health. Furthermore, it is stated that people with heavily pigmented skins often have poor vitamin D status because of photoprotection by melanin. In this paper we review the effect of photoprotection strategies and pigmentation on vitamin D status. Clothing can clearly be very effective at inhibiting vitamin D synthesis. Sunscreens are effective in theory and some limited human studies support this. However, most studies show little or no effect and the most likely reason for this is that sunscreens have not been applied in the manner that was used to determine their labelled index of protection against sunburn. This could change in the future if public health campaigns and the sunscreen industry are successful in encouraging the public to apply sunscreens more liberally and/or use much higher levels of labelled protection. The role of melanin on vitamin D status is not clear and requires further investigation.