Should I prescribe sunlight instead of vitamin D?

CMAJ • NOVEMBER 23, 2010 • 182(17) © 2010 Canadian Medical Association or its licensors E802 With the increased understanding of the effects of vitamin D on the body and the growing evidence that people living in northern climes have inadequate levels of vitamin D during the winter months, I wondered whether I should be prescribing sunlight for my patients. After all, a mild sunburn after 5 to 10 minutes of sun exposure in the peak of summer can synthesize as much as 20 000 IU of vitamin D — 20 days’ worth of the often recommended 1000 IU vitamin D supplement taken daily. We all know that a sunburn is not good for your skin, but what about a more modest tan? If I were to go out for four minutes at lunchtime on a sunny day in July wearing shorts and a T-shirt, my body would generate about 1000 IU of vitamin D (I am fair with freckles). That seems reasonable, doesn’t it? A person with darker skin colour would need to enjoy some additional time in the sun to achieve the same result, but I suspect that my patients would be very happy to receive such a prescription and that adherence to my advice would be quite high. According to the American Academy of Dermatology and the Canadian Dermatology Association position statements on vitamin D, however, I would be doing my patients a serious disservice. These groups are clear that there is no scientifically validated, safe threshold level for ultraviolet exposure from the sun (or indoor tanning devices) that allows for appropriate vitamin D synthesis without increasing the risk of skin cancer. Encouraging patients to increase their exposure to the sun is a bad idea. Instead, the groups recommend that physicians discuss the use of oral vitamin D supplements, particularly for the winter months, with their patients. Not everyone agrees with the dermatologists; instead some decry the demonization of sunlight and argue that people are unlikely to take vitamin supplements ad infinitum. But I’m siding with the dermatologists on this one. In short, the answer is no to prescribing sunlight for my patients. Instead, oral vitamin D supplements and sunblock are healthier topics for discussion. Now I just have to figure out a way to persuade my patients to take their vitamins.