It’s getting warmer out here on the West Coast, and you know what that means! The days are getting longer, the sunlight is getting more intense, and people are getting ready. And as the sunshine picks up, tubes of sunscreen are being dug out of medicine cabinets and random drawers. Although this year has had a very atypical start, it is nonetheless important that people properly equip themselves.
Why do we rush to slather on sunscreen the moment we notice the weather outside getting warmer and the sun’s rays getting stronger?
This has to do with the amount of ultraviolet radiation that is present in sunlight—in particular, ultraviolet A (UVA) and ultraviolet B (UVB) (1). UVA radiation carries less energy than UVB radiation and may cause the skin to wrinkle (2). In contrast, UVB is more intense and therefore is the main cause of sunburns; it is also linked to various types of skin cancer (1). Sunscreen is recommended as an effective way to reduce the harmful effects of UV radiation. However, UVB is not all bad; it triggers vitamin D production in the skin.
Vitamin D fulfills several important functions in the body:
This raises the following question: How does sunscreen affect vitamin D production in your skin?
Various studies have tried to interpret the relationship between sunscreen and sun exposure, and the results have been mixed. Some studies posit that sunscreen may interfere with the way in which the body absorbs sunlight, unfortunately compromising vitamin D status (1). Other studies have suggested that sunscreen does not create a significant decrease in vitamin D synthesis.
A 2019 article published in the British Journal of Dermatology tried to evaluate how much two different sunscreen types prevented vitamin D production in the sun. Out of the 79 research subjects, 62 members spent a weeklong vacation on the island of Tenerife, while 17 stayed behind as the control group. The travelers experienced clear skies and a UV index of up to 9. (To provide context, an index of 0-2 is rated low, 3-5 moderate, 6-7 high, 8-10 very high, and 11+ extreme.)
The research subjects were broken up into four groups: the first used sunscreen lotion with a sun protection factor (SPF) of 15 with high UVA protection, the second used an SPF 15 sunscreen lotion with low UVA protection, the third used their own preferred sunscreen, and the control group stayed behind in their hometown of Łódź, Poland. The first and second groups were instructed on how to correctly apply sunscreen, while the discretionary group applied as they normally would. To properly analyze the sample, the researchers collected data on the subjects’ behavior, clothing coverage, UVA/B exposure, and degree of sunburn.
At the end of the study, the two groups applying SPF 15 both showed statistically significant increases in the amount of vitamin D that their bodies produced during the holiday (1). This means that their skin was still properly assessing and producing the vitamin despite being covered with sunscreen. Over the course of the study, the holiday groups spent more than 35 hours out in the sun (2). The only study group to suffer from sunburns was the discretionary group who were not instructed on how to appropriately apply sunscreen. As Antony Young, PhD, said about the study, “The important message is that doses for vitamin D production are much lower than for sunburn. That means you can still get enough sun to trigger vitamin D even when you put on enough sunscreen to guard against burns.”
Therefore, it is important that you apply the type of sunscreen most suitable for the length of time that you plan to spend outdoors. You should not go out into the sun without the appropriate sunscreen, keeping in mind what activities you want to do and how much coverage you need. (Beachgoers and water sports enthusiasts, you should use water-resistant versions that won’t run into your eyes; a zinc-based lotion is a good option. And make sure to re-apply often!) Sunscreen is helpful in the prevention of premature wrinkles in the sun and lowering the risk of developing skin cancer (2). The idea is to practice caution.
In light of the current outbreak situation, it is necessary that we all practice social distancing and significantly limit the amount of time that we spend outside. You can get the proper nutrients through a healthy, robust diet and the addition of vitamin supplements like vitamin D. Once things get better and it is safe to head out, enjoy going out in the sun, but don’t forget to bring the sunscreen lotion!
1. Young, A., Narbutt, J., Harrison, G., Lawrence, K., Bell, M., O'Connor, C., Olsen, P., Grys, K., Baczynska, K., Rogowski‐Tylman, M., Wulf, H., Lesiak, A. and Philipsen, P. (2019). Optimal sunscreen use, during a sun holiday with a very high ultraviolet index, allows vitamin D synthesis without sunburn. Br J Dermatol, 181: 1052-1062. doi:1111/bjd.17888
2. Drayer, L. (2019). Could sunscreen cause Vitamin D deficiency? Short answer: Yes. CNN Health. Retrieved from https://www.cnn.com/2019/09/18/health/vitamin-d-deficiency-sunscreen-wellness/index.html