Cancer myth: Sunscreen, Vitamin D and Cancer

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Origin of the myth

Some companies have advertised that their sunscreen products do not contain the carcinogenic (cancer-causing) substances which other sunscreens contain. In particular, manufacturers of “holistic” and “all-natural” sunscreen make this claim.  The substances said to be possibly carcinogenic are nanoparticles of titanium dioxide and zinc oxide, and the molecules octyl methoxycinnamate, oxybenzone and 4-methyl-benzylidene.

In addition, limited exposure to sunlight can cause vitamin D deficiencies, which may also lead to cancer.

Current evidence

Sunscreen

The US Report on Carcinogens is a list of known or reasonably anticipated human carcinogens (cancer causing substances).  None of the suspect ingredients, listed above, are included in this list.1  In 2010, the International Agency for Research on Cancer (IARC) reviewed the scientific literature on titanium dioxide and concluded that there was inadequate evidence that it causes cancer in humans.2 None of the other ingredients has been classified by the IARC.3,4  These ingredients have been approved for use in sunscreens by the Food and Drug Administration (FDA) in the US and by the European Union.

In response to claims that sunscreen causes skin cancer, a 2003 review examined the link between sunscreen use and melanoma.  No evidence for increased risk of melanoma with sunscreen use was found.  The research suggested that sun-sensitive people who have higher risk of melanoma are more likely to use sunscreens.5

In August 2013,the Therapeutic Goods Administration (TGA) conducted an updated review of the scientific literature available on the use of nanoparticles in sunscreens, in particular zinc oxide and titanium dioxide.6 The TGA review concluded that, “on current evidence, neither of these nanoparticles is likely to cause harm when used as ingredients in sunscreens”. An Australian study published in 2011 showed that regular use of sunscreen was effective in reducing incidence of melanoma, the most serious form of skin cancer.7

Vitamin D

Vitamin D is required for good health. It is produced when our skin is exposed to UV radiation. There has been recent speculation that reducing exposure to sunlight through measures such as using sunscreen may lower vitamin D levels in the body, causing a range of health problems.

Based on the best available evidence, Cancer Council WA recommends that people living in Perth or locations south of Perth receive 30 minutes of sun exposure, close to midday, on most days during June and July. At this time the UV Index is usually below 3 so sun protection is not required.

For the rest of the year, research indicates that Western Australians can get enough vitamin D from incidental sun exposure while conducting their day-to-day activities and using sensible sun protection.8,9 People living in the mid to northern parts of Western Australia should use sun protection all year round whenever the UV index is 3 or above.

While sunscreen could theoretically block vitamin D production entirely, in practice it has not been shown to do so.14-17 Research indicates that sunscreen is rarely applied correctly and that incidental exposure to UV is enough to produce the required amounts of vitamin D.

The Australian Health Survey found that only 6% of the Australian population have moderate or severe vitamin D deficiency (defined as being <30 nmol/L).10

The issue of safe sun exposure for vitamin D is subject to considerable debate at this time. People who are especially concerned about this are advised to refer to Cancer Council WA frequently.

Summary

There is no evidence that use of sunscreens increases the risk of skin cancer or causes vitamin D deficiency.11,12 Meanwhile, there is definitive evidence that sun exposure increases the risk of skin cancer.  Solar radiation is classified as a known human carcinogen in the Report on Carcinogens.1  IARC also classifies solar radiation as carcinogenic to humans.13

Further reading

References

  1. U.S. Department of Health and Human Services Public Health Service National Toxicology Programme, 12th Report on Carcinogens, in National Institute of Environmental Sciences. 2011
  2. International Agency for Research on Cancer (AIRC) IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 93 - Carbon Black, Titanium Dioxide and Talc, 2010.
  3. International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans  2007 , IARC: Lyon, France.
  4. International Agency for Research on Cancer (IARC), Agents Classified by the IARC Monographs. 2011.
  5. Dennis, L.K., L.E. Beane Freeman, and M.J. VanBeek, Sunscreen use and the risk for melanoma: a quantitative review. Ann Intern Med, 2003. 139(12): p. 966-78.
  6. Therapeutic Goods Administration (TGA), Literature Review on the Safety of Titanium Dioxide and Zinc Oxide Nanoparticles in Sunscreen - Scientific Review Report. 2013, Australian Government - Department of Health and Ageing.
  7. Green AC, Williams GM, Logan V, Strutton GM Reduced Melanoma After Regular Sunscreen Use: Randomized Trial Follow-Up, Journal of Clinical Oncology, 20 January 2011; 29(3) 
  8. Sinclair, C., Risks and benefits of sun exposure: implications for public health practice based on the Australian experience. Prog Biophys Mol Biol, 2006. 92(1): p. 173-8.
  9. Sollitto, R.B., K.H. Kraemer, and J.J. DiGiovanna, Normal vitamin D levels can be maintained despite rigorous photoprotection: six years' experience with xeroderma pigmentosum. J Am Acad Dermatol, 1997. 37(6): p. 942-7.
  10. Australian Bureau of Statistics (ABS) Feature Article - Vitamin D. July 2014 [cited on 14/08/2014] Available at: http://www.abs.gov.au/ausstats/abs@.nsf/Latestproducts/E31CBC051F4F6EA8CA257CBA00128C83?opendocument
  11. Berwick, M., Counterpoint: sunscreen use is a safe and effective approach to skin cancer prevention. Cancer Epidemiol Biomarkers Prev, 2007. 16(10): p. 1923-4.
  12. Green, A.C. and G.M Williams, Point: sunscreen use is a safe and effective approach to skin cancer prevention. Cancer Epidemiol Biomarkers Prev, 2007. 16(10): p. 1921-1922.
  13. International Agency for Research on Cancer (IARC), Solar and ultraviolet radiation, in IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. 1997, IARC: Lyon, France.
  14. Marks R, Foley PA, Jolley D, Knight KR, Harrison J, Thompson SC. The effect of regular sunscreen use on vitamin-D levels in an Australian population - results of a randomized controlled trial. Archives of Dermatology 1995; 11(4): 415-421.
  15. Farrerons J, Barnadas M, Rodriguez J, Renau A, Yoldi B, Lopez-Navidad A, Moragas J. Clinically prescribed sunscreen (sun protection factor 15) does not decrease serum vitamin D concentration sufficiently either to induce changes in parathyroid function or in metabolic markers. British Journal of Dermatology 1998; 139(3): 422-427.
  16. Farrerons J, Barnadas M, Lopez-Navidad A, Renau A, Rodriguez J, Yoldi B, Alomar A. Sunscreen and risk of osteoporosis in the elderly: A two-year follow-up. Dermatology 2001; 202(1): 27-30.
  17. Norval, M, Wulf HC. Does chronic sunscreen use reduce vitamin D production to insufficient levels? British Journal of Dermatology 2009; 161(4): 732-736.

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