Thursday, September 17, 2009

Sun vs. Skin

I have found myself in a conundrum this term at school—I love the sun, but I love my skin too and want to continue to love it when I am 60. I am completing a rotation with a dermatologist, which has been one of the highlights of my clinical education thus far and has made me realize that I need to pay more attention to sun protection. I listen to her tell all of her patients about sunscreen and recommend that they slather it on daily, whether its sunny, rainy, cloudy, if they plan to be outside, if they plan to be indoors, if they ride in a car, etc. The dermatological experts have strong evidence to make these recommendations given the incidence of skin cancers and the known preventative benefit that sunscreen provides. My question is though, how will anyone following this recommendation ever get enough vitamin D?

Why the sun isn’t enough (and for skin’s sake—shouldn’t be):
  • Sunscreen over SPF 8 will block the sun’s ability to make vitamin D
  • Caucasians need approximately 20 minutes per day between 10 and 2pm of direct sunlight, most of skin uncovered, to make their daily dose of vitamin D
  • African-Americans, or other dark skinned individuals, need approximately 1 hour to make their daily dose
  • The ability to make vitamin D depends at latitude and time of year. In areas north of 35-37 degrees latitude, little to no vitamin D is made November to February.

So between the sunscreen, lack of time outside during daylight hours and varying geographical chance of exposure, its no surprise so many people are vitamin D deficient. I was reviewing lab results today for an African American female, living in Arizona, and her vitamin D level (measured as 25-OH D3) was 7 ng/ml—the normal value is between 20-100 ng/mL! Low vitamin D has been associated with conditions ranging from musculoskeletal pain, metabolic syndrome, cardiovascular disease, depression, and immune dysfunction-- just to name a few. According to many, optimal levels for disease prevention should be between 40-60 ng/mL.

The recommended supplemental dose of vitamin D varies by healthcare practitioner and depends on the individual. The recommended adequate intake, according to the Institute of Medicine is 200 IU’s per day, which really is only adequate in that it prevents rickets. According to the American Academy of Dermatology’s position statement on Vitamin D, “Adults who regularly and properly practice photoprotection may also be at risk for vitamin D insufficiency, and may be considered for a daily total dose of 1000 IU vitamin D.”

Diet is the only other source of vitamin D and is found in a limited number of foods. Many people rely on their milk intake as an adequate dose, but unless you find yourself drinking approximately 10 eight ounce glasses of milk fortified with vitamin D per day, you might not be getting a therapeutic dose through diet alone.

Diet, supplementation and sun are the only options in this game. With the potential harm that the sun can cause and the dietary challenge of obtaining therapeutic doses, it seems like an easy solution to the battle is to have blood levels checked and simply take some vitamin D. Here are some additional resources about vitamin D:

Harvard Article on the Need for More D

D Research and Common Conditions Associated with Insufficiency
American Academy of Dermatology Position Statement on Vitamin D

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