May 6, 2014

expert reaction to study linking over-avoidance of sun to skin cancer

Research published in the Journal of Internal Medicine reported that Swedish women who avoided sun exposure were at an increased risk of skin melanomas due to low vitamin D levels.

Yinka Ebo, senior health information officer at Cancer Research UK, said:

“This study only looked at whether sun exposure levels in Swedish women were linked to death rates, so it can’t tell us anything about the role of vitamin D levels. And the reasons behind higher death rates in women with lower sun exposure are still unexplained, as unhealthy lifestyle choices could have played a part.

“Overexposure to UV radiation from the sun or sunbeds is the main cause of skin cancer. We all need some sunshine to make vitamin D for healthy bones. Enjoying the sun safely while taking care not to burn should help most people strike a good balance. The best way to protect your skin from sunburn is to spend time in the shade or pop a t-shirt on when you’re out in strong sun, and use a minimum of SPF15 sunscreen to help protect the bits you can’t cover.”

Dr Andrea Darling, Post-doctoral Research Fellow from the University of Surrey, said:

“The jury is still out on the issue of obtaining vitamin D from sunlight.  There is some evidence that vitamin D may be important for reducing the risk of many cancers, however there is also strong evidence that skin cancer is caused by sun bathing. 

“This creates a dilemma – do we recommend sun bathing to improve vitamin D status?   The problem is that there is some evidence that vitamin D is protective against skin cancer, but this benefit may be outweighed by the detrimental effects of the sun’s ultraviolet B (UVB) rays.

“The findings from Dr Lindqvist’s team are interesting, but it is possible that the women in the study who had high sun exposure differed from the women who had low sun exposure in ways that may explain their reduced cancer risk.  This means the same result may not be seen again when other researchers do similar studies.

“Sun exposure should still be undertaken in accord with the vitamin D guidelines suggested by Cancer Research UK http://sunsmart.org.uk/UV-the-sun-and-skin-cancer/vitamin-d/.  Vitamin D can also be obtained from foods in the diet (e.g. oily fish, eggs, spreads) and from vitamin D supplements.”

Prof Dorothy Bennett, Professor of Cell Biology at St. George’s, University of London, said:

“The conclusion of this study is not simply, ‘The more sun the better’.  The authors still agree that ultraviolet light is the main cause of skin cancer.  Rather, the findings support the consensus that the ideal amount of sun exposure for Northern Europeans is ‘a little’, rather than zero.  Today’s active sunbathers are likely to use sunscreens and avoid sunburn (not monitored in this study).

“As the authors comment, our bodies need sunlight to make essential vitamin D, which can help us resist some cancer types.  Those who normally avoid the sun and/or cover most of their skin are advised to take vitamin D supplements.

“A rule of thumb is to enjoy a little sun (like 15 min a day on face and arms, in a British summer), but don’t get sunburnt.”

‘Avoidance of sun exposure is a risk factor for all-cause mortality: results from the Melanoma in Southern Sweden cohort’ by P. G. Lindqvist et al. published in the Journal of Internal Medicine on 23rd April 2014.