Sun: Friend or Foe?

The skin functions as a barrier–it protects against germs and maintains proper hydration for the body. An important part of this barrier function is melanin, a pigment in the skin that determines its color and protects against ultraviolet radiation (UVR) from the sun. Melanin does this by accumulating around skin cells’ DNA, shielding them from damaging UVR. [1]

Melanin density is a strong predictor for skin cancer.[2] The skin tone scale is often used as a proxy for melanin density: darker skin with higher melanin density shields against potential cancer-causing rays more effectively than lighter skin.[3] Based on the wide range of skin colors, one size does not fit all when it comes to sun safety.

Sun exposure needs are not the same for all ethnicities. White individuals are 70 times more likely to develop skin cancer than people with darker skin.[4] People of lighter skin color also tend to develop symptoms like abnormal moles, meaning they are more likely to be diagnosed during earlier cancer stages when there is still time for effective treatment. This becomes especially important when dealing with melanoma, the rarest but deadliest skin cancer. White individuals have a 93% survival rate, while the rate for black patients is only 69%.[5] Since people with darker skin have more sun protection but tend to receive later skin cancer diagnoses, regular skin checks with a doctor are all the more important for them.

You are more likely to experience sunburns if you have lighter skin than darker skin. While lighter-skinned people are more susceptible to skin cancer, those with darker skin are more likely to be vitamin D deficient. Source: D’Orazio et al./Influence of pigmentation on skin cancer risk/CC BY 3.0

Go to a doctor for a skin check if you notice any abnormalities or recent changes, for example, a new or growing mole. An important step you can take is self-screening for skin abnormalities, using the alphabet of skin cancer [6]. This means being on the lookout for moles that:

  1. are asymmetrical in shape
  2. have uneven borders
  3. have a variety of colors
  4. are large in diameter (larger than an eraser on the end of a pencil)
  5. evolve over time

 

UVR exposure is a risk factor for skin cancer, but it is also necessary for the body to produce vitamin D. Vitamin D is essential because it helps you absorb calcium and protects against colorectal cancer.[7, 12] Deficiency is associated with chronic diseases like heart disease, immune disorders, and depression.[2, 4]

Black and Hispanic populations are at the highest risk for vitamin D deficiency, most likely because of the higher density of melanin in their skin.[8] While all people can benefit from extra sunshine, it is extremely important that people with darker skin get UVR exposure.

Since it is difficult to get sufficient amounts of vitamin D through food, frequent sun exposure and outdoor activities are crucial. In particular, people who spend their workdays indoors at computer-centered jobs, for example, or those who depend on indoor activities for entertainment, should make an extra effort to get a daily dose of sunshine. While it is important to promote sun safety and sunscreen usage, a little vitamin D may go a long way for cancer prevention. Being outside during the middle of the day for 3-15 minutes for people with lighter skin and 15-30 minutes for people with darker skin should do the trick. If you spend more time than that outdoors, you should wear sunscreen to protect yourself from burns.[9] The bottom line is that sunlight, like anything else, is best in moderation.

 

References
  1. Brenner, Michaela, and Vincent J. Hearing. “The Protective Role of Melanin Against UV Damage in Human Skin†.” Photochemistry and Photobiology, vol. 84, no. 3, 2007, pp. 539–549., doi:10.1111/j.1751-1097.2007.00226.x
  2. Dwyer, T. “Cutaneous Melanin Density of Caucasians Measured by Spectrophotometry and Risk of Malignant Melanoma, Basal Cell Carcinoma, and Squamous Cell Carcinoma of the Skin.” American Journal of Epidemiology, vol. 155, no. 7, Jan. 2002, pp. 614–621., doi:10.1093/aje/155.7.614.
  3. Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium; Ross AC, Taylor CL, Yaktine AL, et al., editors. Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US); 2011. 3, Overview of Vitamin D. Available from: https://www.ncbi.nlm.nih.gov/books/NBK56061/
  4. Halder RM, Bang KM. Skin cancer in blacks in the United States. Dermatol Clin. 1988;6:397–405.
  5. Cancer Facts and Figures 2017. American Cancer Society.  http://www.cancer.org/acs/groups/content/@editorial/documents/document/acspc-048738.pdf.
  6. Skin Cancer Foundation. (2018). Retrieved February 08, 2018, from https://www.skincancer.org/skin-cancer-information/melanoma/melanoma-warning-signs-and-images/do-you-know-your-abcdes
  7. Nair, Rathish, and Arun Maseeh. “Vitamin D: The ‘sunshine’ Vitamin.” Journal of Pharmacology & Pharmacotherapeutics 3.2 (2012): 118–126. PMC. Web. 1 Feb. 2018.
  8. Ginde AA, Liu MC, Camargo CA. Demographic Differences and Trends of Vitamin D Insufficiency in the US Population, 1988–2004. Archives of internal medicine. 2009;169(6):626-632. doi:10.1001/archinternmed.2008.604.
  9. Mead MN. Benefits of Sunlight: A Bright Spot for Human Health. Environmental Health Perspectives. 2008;116(4):A160-A167.

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