Sunscreen photoprotection and vitamin D status

Abstract

Background: Global concern about vitamin D deficiency has fuelled debates on photoprotection and the importance of solar exposure to meet vitamin D requirements.

Objectives: To review the published evidence to reach a consensus on the influence of photoprotection by sunscreens on vitamin D status, considering other relevant factors.

Methods: An international panel of 13 experts in endocrinology, dermatology, photobiology, epidemiology and biological anthropology reviewed the literature prior to a 1-day meeting in June 2017, during which the evidence was discussed. Methods of assessment and determining factors of vitamin D status, and public health perspectives were examined and consequences of sun exposure and the effects of photoprotection were assessed.

Results: A serum level of ≥ 50 nmol L^-1 25(OH)D is a target for all individuals. Broad-spectrum sunscreens that prevent erythema are unlikely to compromise vitamin D status in healthy populations. Vitamin D screening should be restricted to those at risk of hypovitaminosis, such as patients with photosensitivity disorders, who require rigorous photoprotection. Screening and supplementation are advised for this group.

Conclusions: Sunscreen use for daily and recreational photoprotection does not compromise vitamin D synthesis, even when applied under optimal conditions. What's already known about this topic? Knowledge of the relationship between solar exposure behaviour, sunscreen use and vitamin D is important for public health but there is confusion about optimal vitamin D status and the safest way to achieve this. Practical recommendations on the potential impact of daily and/or recreational sunscreens on vitamin D status are lacking for healthy people. What does this study add? Judicious use of daily broad-spectrum sunscreens with high ultraviolet (UV) A protection will not compromise vitamin D status in healthy people. However, photoprotection strategies for patients with photosensitivity disorders that include high sun-protection factor sunscreens with high UVA protection, along with protective clothing and shade-seeking behaviour are likely to compromise vitamin D status. Screening for vitamin D status and supplementation are recommended in patients with photosensitivity disorders.

Figure 1

Factors that affect the synthesis of vitamin D₃. Many factors determine vitamin D₃ production. The most important external factor is UVB dose, which is the product of UVB intensity (irradiance) and exposure time. Cutaneous pre‐vitamin D₃ is synthesized from 7‐dehydrocholesterol after UVB exposure. Thermally converted into vitamin D₃, it then binds to vitamin D binding protein (DBP) in the blood to be activated sequentially by the liver and kidney. Cytochrome P450 (CYP) enzymes are crucial for the synthesis of biologically active vitamin D₃ (calcitriol), which binds to intracellular vitamin D receptor (VDR) in most cells in the body. Adapted from Jolliffe et al.14 More details of these factors are given in the Supporting Information. BSA, body surface area; RXR, retinoid X receptor; VDRE, vitamin D response element.

Figure 2

Thresholds of serum 25(OH)D concentration recommended by different bodies for definitions of vitamin D status (adapted from Bouillon23). Red, deficiency; orange, insufficiency; green, sufficiency. AAP, American Academy of Pediatrics; AGS, American Geriatrics Society; DACH, Deutschland, Austria and Confederation Helvetica; GRIO, French Research and Information Group on Osteoporosis; IOF, International Osteoporosis Foundation; IOP, Institute of Medicine; SACN, Scientific Advisory Committee on Nutrition (U.K.).

Figure 3

Ultraviolet radiation (UVR) spectra and their interactions with action spectra. (a) UVR emission spectra of natural temperate noon summer sunlight (London, U.K.; 51·5° N), solar simulated radiation (SSR) from a Solar^® Light 16S‐001 v4·0 (Solar^® Light, Glenside, PA, U.S.A.) with an emission spectrum compliant for sun‐protection factor (SPF) testing with the International Organization for Standardization (ISO) Standard 24444 and Cosmetics Europe 2006 and a UVB phototherapy source (Philips TL20W/12 fluorescent tubes in combination with and without a UVC blocking filter (Kodacel) that has been widely used in vitamin D studies. Spectra are normalized at 315 nm (CIE boundary between UVB and UVA). (b) CIE action spectra for erythema57 and formation of pre‐vitamin D₃.58 (c) UVR emission spectra weighed for erythema and pre‐vitamin D₃ using the emission spectra in Figure 3a and action spectra in Figure 3b. These products give biologically effective energy and are normalized at 315 nm (CIE boundary between UVB and UVA). Comparisons of the UVB source, with and without Kodacel, weighted with the pre‐vitamin D action spectrum show the large influence of nonsolar UVR in many laboratory studies. Comparisons of the London solar spectrum weighted with the erythema and pre‐vitamin D action spectra show that UVA filters have no influence on vitamin D production.