With the increasing rates of skin cancer globally, the message about effective sun protection has never been stronger. The use of sunscreens, when used properly, have been shown to be effective in reducing skin erythema due to UVB radiation – the precursor to sunburn and a significant risk factor for the development of skin cancers including malignant melanoma. The downside to their use, which has been debated, is their potential effect on reducing vitamin D production. Despite dietary sources of the vitamin (oily fish, egg yolks, fortified cereals and milk) being available around, 80% - 90% of the vitamin is obtained by skin exposure to UVB radiation from the sun. As sunscreens reduce the amount of UVB reaching the skin, there is the theoretical risk of them to reduce (or even halt) vitamin D production by the body.
Vitamin D3 synthesis occurs when 7-dehydrocholesterol, present in epidermal keratinocytes, interacts with UV light (at the 270nm-300nm wavelength). From here, the vitamin is hydroxylated in the liver to form 25 hydroxy vitamin D and released into the circulation. The kidney then undertakes the conversion of the vitamin to its most biologically active form - 1,25-dihydroxyvitamin D. The vitamin is known to be essential for normal calcium and phosphorus metabolism which in turn is required for normal bone development. There has been much discussion within the media about the potential effects of the vitamin in the prevention of certain types of cancers, but to date there has been no clear evidence that higher levels of the vitamin may actually protect against their development.
In a forthcoming paper, to be published in the British Journal of Dermatology (1), researchers have investigated the effects of using SPF-15 sunscreen on vitamin D production amongst holidaymakers. The study compared two SPF-15 sunscreen formulations (one with high UVA protection, the other with low UVA protection) amongst 40 Polish holidaymakers visiting Tenerife. These two groups (educated on its application and issued with 50 grams tubes of sunscreen to use three times daily) were compared with a third holiday group given sunscreen without any instructions. In addition, a fourth, non-holidaying group was included as a control. The results concluded that both the study holiday groups using sunscreens had a statistically significant rise in vitamin D3 levels, whilst the non-holidaying control group back home showed a small drop during the same period. Interestingly, the sunscreen with high UVA factor showed greater increases in vitamin D – as this allows greater UVB transmission.
What this work strongly suggests is that even when using a sunscreen to optimal conditions during a sunny / high UV index holiday, vitamin D production within the skin is continuing, and their use does not significantly reduce vitamin D levels. This work concurs with another forthcoming publication in this journal (2). A comprehensive systematic review of 75 studies covered all published experimental and real-life studies to answer the same question and reached similar conclusions – that the use of sunscreens in real life conditions are unlikely to affect vitamin D production. The only question which remains to be adequately tested in whether the high SPF (30+) sunscreens have a similar, limited effect on reducing vitamin D production but the authors conclude for now the benefits of sunscreen use in skin protection outweigh the risk of vitamin D deficiency and their use should be continued to be advised.
References
1. Young AR, Narbutt J, Harrison GI, Lawrence KP, Bell M, O'Connor C, et al. Optimal sunscreen use, during a sun-holiday with a very high UV index, allows vitamin D synthesis without sunburn. Br J Dermatol. Early view
2. Neale RE, Khan SR, Lucas RM, Waterhouse M, Whiteman DC, Olsen CM. The effect of sunscreen on vitamin D: a review. Br J Dermatol. Early view.