Correct Use of Sunscreen Allows Vitamin D Production 

Becky McCall

May 09, 2019

Vitamin D (25-hydroxyvitamin D3 [25(OH)D3]) production is not inhibited by the use of sunscreen, when used correctly to prevent sunburn, shows a study where participants used sun protection factor (SPF)15 during a week-long holiday in Tenerife.

The study, published in this week's British Journal of Dermatology (BJD), also found that sunscreens with a high ultraviolet (UV) A protection, compared to those with low UVA protection actually encourage vitamin D synthesis. The authors note that this effect is most likely due to greater transmission of UVB in the sunscreens with high UVA protection factor (UVB generates vitamin D). 

Another two studies also recently published in the same journal support these findings. One is a systematic review of 75 papers, and the other a further review based on findings of an international panel of experts who reviewed scientific literature on vitamin D and sun protection. The latter concluded that sunscreen use is unlikely to affect vitamin D production and that UVA protection does not affect vitamin D synthesis.

Antony Young, PhD, emeritus professor of experimental photobiology at King's College London (KCL), was lead author of the Tenerife study. "Sunlight is the main source of vitamin D, and sunscreens can prevent sunburn and skin cancer, but there has been a lot of uncertainty about the effects of sunscreens on vitamin D production," he explained, adding that, "this study, during a week of perfect weather in Tenerife, showed that sunscreens, even when used optimally to prevent sunburn, allowed excellent vitamin D synthesis."

High UVA Sunscreen Has Lower UVB Protection but Stimulates More Vitamin D Production

Around 80% of vitamin D is acquired from exposure to the sun's rays, with UVB initiating cutaneous vitamin D3 synthesis. Vitamin D is essential for skeletal integrity and has been associated with many other health benefits, but solar UV radiation (UVR) is responsible for an increasing incidence of melanoma, basal cell carcinoma and squamous cell carcinoma, particularly in people with pale skin.

However, there have been conflicting results around the role of sunscreens in affecting vitamin D production, with different studies reaching different conclusions. Laboratory-based studies support the theoretical risk that sunscreen use may affect vitamin D levels, but these studies used UVR sources that were very different from solar UVR.

In light of this, the study aimed to assess the ability of two sunscreens to inhibit 25(OH)D3 synthesis during a week-long sun holiday in Tenerife, and to compare these sunscreens, under optimal use, with typical sunscreen use.

An SPF 15 formulation with high UVA protection enabled better vitamin D synthesis than a low UVA protection product, because the former allows more UVB transmission. 'This would be expected to have a beneficial effect on vitamin D synthesis,' write the authors.

In the study by Young and colleagues, 40 healthy Polish participants were randomly assigned in equal numbers to two groups each using a different SPF15 formulation during a 1-week sun holiday in Tenerife (28° N). The UVA protection factor was low in one case and high in the other – the SPF with high UVA had lower UVB protection. All participants were healthy adults with no skin conditions or histories of vitamin D supplementation, nor had any used sunbeds.

Participants were advised on the correct application. "Regulatory authorities specify an application thickness of 2 mg cm2 skin, for SPF tests however, people typically apply much less, for example 0.8 mg cm2, reducing the SPF. People often apply cream in a patchy way missing areas of exposed skin," remarked Antony Young.

Comparisons were also made with discretionary (or typical) sunscreen use in 22 participants who were not instructed in any way in how to apply their own sunscreen while in Tenerife, and another group of 17 who stayed in Poland. Sunscreen use in the intervention groups was measured, as were behaviour, UVR exposure via a wrist-worn device, clothing cover and sunburn. Blood tests before and after the holiday provided measures of serum 25(OH)D3. The primary endpoint was change in 25(OH)D3 production.

Holiday Groups Showed Increase in 25(OH)D3 Levels

The vitamin D increase in all holiday groups was statistically significant (P<0.001), while the group that remained in Poland had a slight fall in vitamin D level.

"The broad-spectrum sunscreen allowed a little more UVB through and as might be expected, and this enabled better vitamin D synthesis. The greatest increase in vitamin D was seen in the discretionary use group, but this group had a high level of daily sunburn on five exposed body sites compared to the intervention groups (P<0.001)," reported Antony Young.

No difference was seen in sunburn between the two intervention sunscreens (P>0.3). "Sunscreen intervention groups did not have sunburn but both had a highly significant increase in vitamin D level (P < 0.001), with broad spectrum sunscreen having a significantly greater increase than the low UVA-protection factor sunscreen," added the researcher. The high UVA protection factor group showed an increase in vitamin D of 19.0 ± 14.2 nmol L–1 25(OH)D3, while the low UVA protection factor group showed an increase of 13.0 ± 11.4 nmol L–1 25(OH)D3.

Asked whether the study results might apply to use of sunscreens with high SPFs, Antony Young replied that, "Volunteers in our study were instructed to use sunscreen properly so they achieved SPF 15. Typically, people use much less sunscreen than used for SPF testing so that somebody using say SPF 50 in a typical way will only get an SPF of about 15," he said, adding that, "Our results apply for typical sunscreen use, but may not apply if the labelled SPF is achieved [if a higher SPF sunscreen is used]. Under these conditions, I would expect much less vitamin D production."

Systematic Review of 75 Studies

The systematic review that was carried out by researchers from the QIMR Berghofer Medical Research Institute, Australia, and the Australian National University, covered all published experimental studies, field trials, and observational studies published between 1970 and 2017, totalling 75 studies, for the first time. The laboratory-based studies using artificial light sources supported the theoretical risk that sunscreen use may affect vitamin D, however real-world evidence from field trials and observational studies involving natural sunlight suggests that the risk is low.

Reflecting on the common concern that sunscreen use may increase the risk of vitamin D deficiency, lead author of the review, Rachel Neale, PhD from the QIMR Berghofer Medical Research Institute said: "This has the potential to undermine sun protection messages, which aim to prevent skin cancer. A 2015 survey conducted in the US found that 20% 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."

Finally, the third study was carried out by an international panel of 13 experts in endocrinology, dermatology, photobiology, epidemiology and biological anthropology. The review was led by Thierry Passeron, PhD, University of the Côte d'Azur, Nice, France. The experts reviewed scientific literature on vitamin D and sun protection prior to an evidence review meeting. They concluded that sunscreen use is unlikely to affect vitamin D production and that UVA protection does not affect vitamin D synthesis.

The studies were published to coincide with the British Association of Dermatologists' (BAD) Sun Awareness Week (6th-12th May). Holly Barber, BAD communications officer, commented on the overall study results. She welcomed the findings but added that: "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."

COI:  

Professor Young: The Tenerife study was funded by an EU Framework 7 project (ICEPURE) that I coordinated but Boots provided some additional support for the intervention sunscreen studies and also formulated the sunscreens. The Passeron review (of which I am the last author) was sponsored by L'Oréal – they brought together an international panel of experts for a one- day discussion after we had prepared our material.

Dr Neale: Funding: has her salaries partially funded by fellowships from the National Health and Medical Research Council (Aust). No other funding was obtained.

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