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Sunscreens used optimally to prevent sunburn, allow excellent vitamin D synthesis

While sunscreen is essential when it comes to protecting people from harmful ultraviolet radiation (UVR) and lowering the risk of skin cancer, some believe sunscreen also reduces vitamin D levels. New research published online ahead of print in the British Journal of Dermatology (May 8, 2019) shows using sunscreen does not prevent vitamin D production.

Vitamin D, which is vital for bone health, is produced by the skin in response to UVR from sunlight. In addition to being the main source of vitamin D, UVR is a known cause of skin cancer.

In the first study, funded by the EU and the Medical University of Lodz, Poland, and conducted by King’s College London, researchers organized participants into four groups. The participants, split from the control group, were sent on a week-long holiday to an area with a high UV index.

Twenty people received a broad spectrum sunscreen with SPF 15, offering UVB protection and high UVA protection. Twenty people received a non-broad spectrum sunscreen, also SPF 15, but with low UVA protection. The two groups were instructed on how to apply sunscreen correctly in order to achieve the labelled SPF.

Another 22 people used their own sunscreen with no instructions on application.

Seventeen people formed a control group and remained in Poland.

The study found SPF 15 sunscreens applied at proper levels to inhibit sunburn allowed a significant improvement of vitamin D levels. The broad spectrum sunscreen enabled higher vitamin D synthesis than a low UVA protective sunscreen, possibly because the former, due to its composition, transmits a little more UVB than the latter.

The group that used their own sunscreens also had significant vitamin D synthesis, but they all also had sunburn. Researchers concluded that this was likely because they did not use their sunscreens correctly.

During the same period, the control group demonstrated a slight decline in vitamin D.

“Sunlight is the main source of vitamin D. Sunscreens can prevent sunburn and skin cancer, but there has been a lot of uncertainty about the effects of sunscreens on vitamin D,” said Professor Antony Young of King’s College London, lead author of the first study. “Our study, during a week of perfect weather in Tenerife, showed that sunscreens, even when used optimally to prevent sunburn, allowed excellent vitamin D synthesis.”

The second study, conducted in Australia by researchers from the QIMR Berghofer Medical Research Institute, reviewed all published experimental studies. Researchers looked at field trials and observational studies published between 1970 and 2017, totalling 75 studies, for the first time.

Researchers found that the experimental studies, using artificial light sources in a laboratory setting, support the theoretical risk that sunscreen use may affect vitamin D levels. However, the weight of evidence from field trials and observational studies, which used real-life situations involving natural sunlight, suggests that the impact on vitamin D levels is low.

According to the researchers, conditions in the experimental studies did not reflect real-world conditions so the results cannot be used to inform public health policy.

Observational studies that showed an association between vitamin D levels and sunscreen use most commonly found a positive relationship, supporting the conclusion that vitamin D synthesis is maintained while wearing sunscreen.

“A common concern amongst the general public is that sunscreen use may increase the risk of vitamin D deficiency,” said Professor Rachel Neale of the QIMR Berghofer Medical Research Institute and lead author of the second study. “This has the potential to undermine sun protection messages, which aim to prevent skin cancer. A 2015 survey conducted in the United States found that 20 per cent of people agreed that regularly protecting the skin leads to a risk of not getting enough vitamin D.

“These recent findings should reduce this concern, and encourage people to follow recommended sunscreen application, which could eventually lead to a reduction in the number of new skin cancer cases.”

A further review presents the findings of an international panel of 13 experts in endocrinology, dermatology, photobiology, epidemiology and biological anthropology, who reviewed scientific literature on vitamin D and sun protection prior to an evidence review meeting also concluded that sunscreen use is unlikely to affect vitamin D production, and that UVA protection does not affect vitamin D synthesis.

“The ability to achieve adequate protection from the sun to avoid sunburn, a risk factor of skin cancer, whilst not impacting vitamin D production is really encouraging,” said Holly Barber of the British Association of Dermatologists. “The risk of vitamin D deficiency from sunscreen has been found to be low, and therefore is unlikely to outweigh the benefits of sunscreen for skin cancer prevention.

“Further research is required on SPF 30 and higher sunscreen, as this is what we recommend people use for optimal protection in real-life situations. People with dark skin types are at a higher risk of vitamin D deficiency, and lower risk of skin cancer, so further research is also required to see how these findings translate to people with dark skin types.”

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