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Sun: Friend or Foe?

source:apod.nasa.gov
source:apod.nasa.gov

Public Health Community Advisory – Break out the dancing elephants and the 76-trombone marching band:  Summer is finally here! As we welcome back our tank tops, shorts, and sandals from their six-month exile, we mustn’t forget the other bare essentials for a fun day in the sun: plenty of water, a hat, and of course, sunscreen. But is all sunlight dangerous? How essential is sunscreen to protecting ourselves from skin cancer, and does one size–or SPF–fit all? Sunlight, or more specifically ultraviolet radiation (UVR), does contribute positively to human health. Sunlight helps with seasonal mood disorders and helps humans produce compounds that fight infection. Our skin’s exposure to UVR helps our bodies produce the active form of vitamin D. Most Americans fall within the healthy range of circulating vitamin D; however, in some studies, more than 60% of African Americans, 40% of Latinos, and more than 80% of youth of some Midwestern Native American Tribes are severely deficient (less than 20ng/ml in blood serum) (3,8,9,) putting them at increased risk for asthma-related hospitalizations, certain cancers, upper respiratory infections (colds), and hospital-acquired infections and death (2,11,12).  One study reported that 86% of African American children with asthma were severely deficient in vitamin D (9).

How do we find a balance between healthy sun exposure, diet, vitamin D supplementation, and sufficient vitamin D levels? First, know your skin type. The Centers for Disease Control and Prevention references the Fitzpatrick Skin Tone Scale (FSTS), with designated levels of I, II, III, IV, V, VI, when discussing skin cancer prevention (1). The website http://www.skincancer.org/prevention/are-you-at-risk/fitzpatrick-skin-quiz

is a good place to start if you are not sure where your skin tone falls on the FSTS. Skin tone is not determined wholly by race but by the type of melanin found in the skin of every human. Pheomelanin is lighter and predominates the skin of FSTS types I and II. Eumelanin is darker and predominates the skin of FSTS types V and VI. Why is this important? It has been stated that melanin is the most perfect protection against UVR photodamage (of skin). Of the two types of melanin, Eumelanin blocks harmful sunlight (UVR) three to six times more effectively, making FSTS types V and VI 70 times less likely to develop skin cancer than those with lighter skin tones I and II (4).

Because there is no free lunch in biology, walking around with skin naturally infused with the equivalent of SPF 4 (SPF is sun protection factor) comes at a cost. If you are an FSTS type IV, V, or VI in North America, the melanin in your skin blocks about 75% of UVR, and you typically will not be able to produce vitamin D at sufficient levels solely from sun exposure. Second, embrace your skin type. If you are an FSTS type I or II, understand that you should protect your skin from harmful sunlight at all times. Your skin has virtually no innate protection from damaging UVR. SPF 30 or higher should probably be worn when in summer sun for extended periods of time. However, types I and II need very little sun exposure to maintain healthy vitamin D levels. If you are a type V or VI, your risk of skin cancer is extremely low because Eumelanin blocks 83%-93% of UVR (5). However, due to geographic, dietary, and cultural factors, types V and VI in North America are at serious risk of vitamin D deficiency-associated disorders.

As a result, everyone—especially those with skin type IV, V, or VI–should have their vitamin D levels evaluated with their primary care physician. Based on your circulating vitamin D levels, you may need to modify your diet and/or take a vitamin D supplement to get within the healthy vitamin D range (30ng/ml-80ng/ml). Also, the appropriate sunscreen SPF should be used according to your skin type and sun sensitivity. One size does not fit all. And if you choose to get your vitamin D the traditional way (unfiltered sunlight), morning sunlight is least dangerous. Talk with your physician about your personal risk of skin cancer, for no one is immune. Knowledge is empowering! Have a healthy summer.

1) National Institutes of Health, Office of Dietary Supplements (ODS). Retrieved from  http://www.cdc.gov/excite/skincancer/mod08.htm

http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

2) Abbas, S., Nieters, A., Linseisen, J., Slanger, T., Kropp, S., Mutschelknauss, E., . . . Chang-Claude, J. (2008). Vitamin D receptor gene polymorphisms and haplotypes and postmenopausal breast cancer risk. Breast Cancer Research, 10(2), 31.

3) Blaney, G. P., Albert, P. J., & Proal, A. D. (2009). Vitamin D metabolites as clinical markers in autoimmune and chronic disease. Annals of the New York Academy of Sciences, 1173(1), 384-390.

4) Brenner, M., Hearing, V. (2008) The protective role of melanin against UV damage in human skin. Photochem Photobiology 84(3):539-549

5) Gloster, H.M. Jr, Neal, K. (2006) Skin cancer in skin of color. J Am Acad Dermatol ;55:741–760. 761–744. quiz.

6) Halder, R.M., Bang, K.M. (1988) Skin cancer in blacks in the United States. Dermatol Clin. 6:397–405.

7) Institute of Medicine, Food and Nutrition Board. (2010). Dietary reference intakes for calcium and vitamin D. Dietary Reference Intake. Retrieved from http://www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-calcium-and-vitamin-D.aspx

(8) Jacobs ET, Alberts DS, Foote JA, Green SB, Hollis BW, Yu Z, Martínez ME Vitamin D insufficiency in southern Arizona. Am J Clin Nutr. 2008 Mar;87(3):608-13.

(9) Litonjua, A. A., & Weiss, S. T. (2007). Is vitamin D deficiency to blame for the asthma epidemic? Journal of Allergy and Clinical Immunology, 120(5), 1031-1035.

(10) Nsiah-Kumi PA, Erickson JM, Beals JL, Ogle EA, Whiting M, Brushbreaker C, Borgeson CD, Qiu F, Yu F, Larsen JL. Vitamin D insufficiency is associated with diabetes risk in Native American children. Clin Pediatr (Phila). 2012 Feb;51(2):146-53.

(11) Peppone, L. J., Rickles, A. S., Janelsins, M. C., Insalaco, M. R., & Skinner, K. A. (2012). The association between breast cancer prognostic indicators and serum 25-OH vitamin D levels. Annals of Surgical Oncology, 19(8), 2590-2599.

(12) Youssef DA, Ranasinghe T, Grant WB, Peiris AN. Vitamin D’s potential to reduce the risk of hospital-acquired infections. Dermatoendocrinol. 2012 Apr 1;4(2):167-75.

 

This article was written by Michael L. McCaskill, MPH, PhD, assistant professor in the UNMC COPH Department of Environmental, Agricultural, and Occupational Health.

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