This may surprise you, but I believe it is a good idea to be checked regularly by a dermatologist to assess any changes that may occur to your skin. That advice, however, is most important for those who do not use tanning beds or get regular sunlight, since more melanomas occur among those who receive little or no UVB (see previous posts).
So let's do a few mathematics. Scientists now estimate that maintaining a vitamin D blood level of 55ng/ml would prevent the breast-cancer deaths of 85,000 US women yearly. Melanoma, on the other hand, takes the lives of about 3,020 women per year. If you assumed that tanning causes 3,020 deaths from melanoma (which it does not), but prevents 85,000 breast cancer deaths, which would you rather take a chance with? Such an analysis, of course, would not even take into consideration the other diseases that are prevented by high vitamin D levels.
For example, Australian researchers did an analysis to determine the risk of death from bone disease that would occur if the anti-sunlight advocates had their way. For the purposes of their analysis, they assumed that sunlight caused melanoma. They then calculated that for every case of melanoma death and disability prevented by avoiding the sun, there would be 2,000 cases of death disability caused by bone diseases alone due to lack of vitamin D. The good news is that sunlight does not cause melanoma; we have already established that regular exposure prevents melanoma.
If Sarah Palin is using her tanning bed in a safe and sane manner, she has one of the best health-promoting devices ever developed. The vitamin D she receives from the UVB light is reducing her risk of twenty cancers and is also reducing her risk of heart disease, osteoporosis, hypertension, MS, lupus, diabetes and approximately 80 more diseases in which vitamin D deficiency is implicated. So Sarah, go ahead and enjoy that tanning bed!
 Garland, C et al. What is the dose-response relationship between vitamin D and cancer risk? Nutrition Reviews 2007;65:S91-5.
 American Cancer Society Statistics 2008.
 Lucas, R, et al. Estimating the global disease burden due to ultraviolet radiation exposure.
Int. J. Epidemiol. Advance Access published February 14, 2008.