Sunscreens and Vitamin D Production

Date: August 2019


Prepared by John Staton - ASCC Technical Committee with acknowledgement of assistance of Dr. Bianca McCarthy and Professor Robyn Lucas

Executive Summary 

  1. 1
    There is credible evidence to support the position that an adequate amount of Vitamin D can still be produced by sun exposure in the presence of sunscreen.
  2. 2
    ASCC supports the position that the risks associated with lack of use of sunscreens outweigh their potential to contribute to Vitamin D deficiency.
  3. 3
    The performance of a sunscreen is largely dependent on how it is used by the end consumer. For maximum protection, sunscreens should be applied at the recommended dose of 2 mg/cm2 and regularly reapplied.
  4. 4
    ASCC recognizes the position of Cancer Council Australia that sunscreen application is not necessary where the Ultra-Violet Index is 3 or less.

Introduction

Sun exposure can be beneficial, with ultraviolet (UV) radiation leading to the synthesis of vitamin D, enhanced mood, reduction in blood pressure, and the treatment of certain skin conditions. However, exposure to UV radiation from sunlight can concurrently lead to DNA damage, immune suppression, and potentially, skin cancer. There are three types of skin cancers causally linked with UV exposure: squamous cell carcinoma, basal cell carcinoma, and malignant melanoma. Australia has the highest skin cancer rates in the world [1,2]. In this region, 2 out of 3 people are predicted to be diagnosed with skin cancer before the age of 70 [2], with individuals of low socio-economic status and those in rural and remote areas being most at risk [3]. Of this cohort, men are significantly more at risk from developing skin cancers, with the Australian Institute of Health and Welfare reporting that in 2010, men had a 1 in 2 chance of developing cancer before the age of 85, while this risk was reduced to 1 in 3 for women [1]. Sunscreens play an important role in protecting the skin against UV.

​The Role of Vitamin D in the Human Body

Solar UVB radiation remains the most effective means to produce vitamin D, which is then converted to the major biologically active form, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). The most well-established role for 1,25(OH)2D3 in the human body is its ability to increase calcium uptake in the intestine, which is important for bone and muscle function. The important role of vitamin D in bone is highlighted in mouse models without the nuclear receptor for 1,25(OH)2D3, vitamin D receptor (VDR). Even with calcium supplementation, these mice have reduced osteoblast numbers and bone volume [5]. When the VDR is replaced specifically in the intestine, calcium homeostasis is normalised [6]. Adequate vitamin D status can have other positive health effects including reduced incidences of colorectal cancer, cardiovascular diseases, depression, metabolic syndrome, type 2 diabetes, and gestational diabetes mellitus [7]. Conversely, vitamin D deficiency may lead to increased risk of mortality [8]. Furthermore, recent evidence has suggested that the topical application of vitamin D metabolites and vitamin D-like compounds can protect against two biological processes triggered by UV exposure: damage of DNA and suppression of the immune system. Vitamin D compounds display strong photoprotective effects by inhibiting these key processes, particularly DNA damage [4]. The origins of these photoprotective benefits are not derived from direct UV absorption or reflection, like a sunscreen. Indeed, these benefits are observed whether 1,25(OH)2D3 is applied either prior to and/or post UV irradiation.

Fig 1. Visualisation of Impact on Body Organs

Reproduced from Sun, Skin and Heath 2014  - Chapter 8

Sunscreens protect against some skin cancers

The role of sunscreen in the protection against UV-induced skin malignancies has been well researched since the first commercial sunscreens were developed in the 1930s. Now, a consistent body of evidence exists that demonstrates that sunscreen provides partial protection against some skin cancers. In a recent study, UV-exposed BRAF (V600E) mice, which are more susceptible to tumourgenesis than wildtypes, showed significantly reduced tumour incidence when treated with SPF 50 sunscreen [8]. While this data shows that sunscreen is effective in reducing skin tumour development, it is not as effective as complete avoidance of UV [8]. This is consistent with current recommendations that seeking shade and wearing protective clothing are the most effective ways to protect against UV [9]. Despite these recommendations, sun exposure is unavoidable and consumers rely heavily on the use of sunscreens.

The efficacy of sunscreens, specifically in humans, was evaluated in a long-term randomised trial in Australia. In this study, participants who applied broad spectrum SPF 15 sunscreen every day for 4.5 years developed half the number of melanoma skin cancers, when compared to the control group, over a 10 year period after the cessation of the study [10]. This result was of borderline statistical significance. Stronger evidence of photoprotection, however, was observed against actinic keratosis [11] and squamous cell carcinoma (SCC) but not against basal cell carcinoma (BCC) [12]. It was estimated that regular sunscreen use in Australia prevented approximately 9.3% and 14% of SCCs and melanomas, respectively [13]. The data from these studies clearly demonstrate that sunscreen provides partial protection against certain types of skin cancers.

The photoprotective benefits of sunscreen arises from the physical and/or chemical barrier that is created between the skin and sun. Sunscreens contain a various mixture of UVA, UVB, and broad spectrum compounds that scatter incident photons and/or absorb incident photons and dissipate the energy [14]. Commonly used UVA filters include butyl methoxy dibenzoylmethane and disodium phenyl dibenzimidazole tetrasulfonate, while commonly used UVB filters include octyl methoxycinnamate, octyl salicylate, homosalate, phenylbenzimidazole sulfonic acid, and octyl triazone [15,16]. Broad spectrum compounds include titanium dioxide and zinc oxide [15,16]. No one filter can be used individually to provide sufficient protection from UV. Therefore, a combination of these filters are used in a sunscreen formulation to effectively reduce the transmission of UV into the epidermal layer.

Where sunscreen may be in conflict with Vitamin D Generation

At certain times of the year and in certain geographic locations the ambient UV Index may be marginal for the production of Vitamin D during incidental sun exposure. Where the UVI is 3 or below, authorities such as Australasian College of Dermatologists, The Bone and Mineral Society of Australia and New Zealand, Osteoporosis Australia and the Endocrine Society of Australia now recommend that use of sunscreen is not necessary and be contra-indicated. [20].

​References

  1. 1
    AIHW; AACR, Cancer in Australia: an overview 2012. Australian Government: Canberra, 2012; Vol. Cancer series no. 74.
  2. 2
    Staples, M. P.; Elwood, M.; Burton, R. C.; Williams, J. L.; Marks, R.; Giles, G. G., Non-melanoma skin cancer in Australia: the 2002 national survey and trends since 1985. Medical Journal of Australia 2006, 184 (1), 6-10.
  3. 3
    National Rural Health Alliance. Skin Cancer in Australia: awareness, early diagnosis and management. http://www.aph.gov.au/DocumentStore.ashx?id=771bc3a6-80ce-4c02-be4d-c735ba0b3ce0&subId=206805 (Accessed November 2014)
  4. 4
    Dixon, K. M.; Norman, A. W.; Sequeira, V. B.; Mohan, R.; Rybchyn, M. S.; Reeve, V. E.; Halliday, G. M.; Mason, R. S., 1alpha,25(OH)2-Vitamin D and a Nongenomic Vitamin D Analogue Inhibit Ultraviolet Radiation-Induced Skin Carcinogenesis. Cancer Prev Res (Phila) 2011, 4 (9), 1485-94.
  5. 5
    Goltzman, D.; Miao, D.; Panda, D. K.; Hendy, G. N., Effects of calcium and of the Vitamin D system on skeletal and calcium homeostasis: lessons from genetic models. The Journal of Steroid Biochemistry and Molecular Biology 2004, 89–90 (0), 485-489.
  6. 6
    Xue, Y.; Fleet, J. C., Intestinal Vitamin D Receptor Is Required for Normal Calcium and Bone Metabolism in Mice. Gastroenterology 2009, 136 (4), 1317-1327.e2.
  7. 7
    Theodoratou, E.; Tzoulaki, I.; Zgaga, L.; Ioannidis, J. P., A., Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational studies and randomised trials. BMJ 2014, 348.
  8. 8
    Viros et al., 2014
  9. 9
    Gies, Roy, Toomey, & McLennan, 1998; Linos et al., 2011
  10. 10
    Green, Williams, Logan, & Strutton, 2011
  11. 11
    (Thompson, Jolley, & Marks, 1993)
  12. 12
    (Green et al., 1999)
  13. 13
    (Olsen et al., 2015)
  14. 14
    (Salinaro et al., 1999
  15. 15
    (Gilbert et al., 2013;
  16. 16
    Rastogi, 2002
  17. 17
    Petersen & Wulf, 2014
  18. 18
    Autier, Boniol, Severi, & Doré, 2001
  19. 19
    Neale, Williams, & Green, 2002),
  20. 20
    Sinclair Vitamin D and sun protection –getting the balance right https://www.cancer.org.au/news/blog/prevention/vitamin-d-and-sun-protection-–-getting-the-balance-right.html
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