Dr. Gabe Mirkin’s Fitness and Health E-Zine
March 10, 2013
At the American Academy of Dermatology meeting in Miami (March, 2013), researchers from Sweden reported that six weeks of ultraviolet light on the full body three times a week (dose of 9 J/cm2) raises blood levels of vitamin D higher than taking pills containing 1,600 IU of vitamin D plus 1,000 mg of calcium for the same length of time. All of the patients were severely vitamin D deficient, with blood levels averaging 20 nmol/L (normal is greater than 75 nmol/L). Ultraviolet light raised blood levels of hydroxy Vitamin D to 75 nmol/L, compared to only 60.6 nmol/L with the pills.
TANNING BEDS DO NOT PROVIDE VITAMIN D: Sun lamp rays are composed of UVB and UVA. UVB are the rays that cause skin to make vitamin D. Although both rays can damage the skin and cause skin cancer, UVB rays are far more potent causes of skin cancer. Therefore manufacturers of sun lamp bulbs usually limit the amount of UVB from their bulbs to less than five percent of the rays they emit. More than 95 percent of rays from sunlamps are usually UVA. So sun lamp bulbs usually cause far more skin damage from the UVA and do not cause the skin to make much vitamin D.
RECOMMENDATIONS: To reduce skin cancer risk, try to avoid exposing areas of skin that have received the most sunlight exposure over your lifetime. Skin cancer is caused by the cumulative exposure to ultraviolet rays, so you should cover the most often-exposed areas of skin: your face, scalp, ears, neck, arms, and back of your hands. For most people, the areas that have received the least exposure are the legs and trunk; however, skin anywhere on your body can develop skin cancer from ultraviolet exposure.
You can get all the vitamin D that you need by exposing a small area of your skin to the sun for 15 minutes a day. If you are outdoors longer than that, you need to cover most of your skin most of the time. We spend about four hours a day riding a bicycle in sunny Florida throughout the year. We wear hats that cover the tops of our ears and necks, put sun screen on our faces, wear sun glasses and bicycle gloves, wear long sleeved shirts or arm coolers to cover our arms, and knickers instead of shorts to cover the top part of our legs to below our knees. Our primary skin exposure to sunlight is on our legs below the knees.