Morsani College of Medicine

Dermatology & Cutaneous Surgery


Sunscreens prevent skin cancer. Some epidemiologic data suggest low levels of vitamin D may increase susceptibility to internal cancer as well as infection, hypertension and autoimmune disorders. Since the sun stimulates production of vitamin D precursors in the skin while sunscreens reduce production it is speculated some of us could be vitamin D deficient and thus at risk for these disorders. Are you now thinking of tossing out your sunscreens and going to the beach or purchasing a package of tanning parlor visits? Hold on! This confusion is a classic example of a “little knowledge is a dangerous thing”.

We have known for many years that sunscreens prevent sunburn and skin cancer by blocking the UVB rays that vary in intensity throughout the year. We now know that longer, more deeply penetrating UVA rays which account for more the 90% of UV light and stay relatively constant throughout the year also play a role in skin cancer as well as skin wrinkling. This is why dermatologists now recommend the newer generation of “broad spectrum” sunscreens that block both groups of rays. SPF rates the amount of UVB protection and the FDA will soon be releasing a new 4-star UVA rating system to quantity the amount of UVA protection. For day to day use (unless you work out of doors or plan recreational sun exposure) a SPF 15 is more than sufficient for most of us. Unfortunately, some commit “sunscreen abuse”, meaning they now go out much longer than before with the false expectation they are getting no sun damage. They may rationalize that by increasing to a SPF 30 they have doubled their protection. Not so fast! A SPF 15 sunscreen blocks 93% of UVB rays, while a SPF 30 blocks 97%–not much additional protection for the increased cost and irritancy!

A few years ago, some studies disclosed a relationship between internal cancer (esp. colorectal cancer) and vitamin D deficiency. In other words, vitamin D perhaps served a “protective” role and since suncreens and/or strict sun avoidance reduced vitamin D production it was speculated by some and politicized by others as a rational to abandon photoprotection altogether. Making matters worse, some suggested that the vast majority of Americans were vitamin D deficient, while others stated the daily recommendation for vitamin D was too low. Some are now promoting increased sunbathing and utilization of tanning salons, despite the mounting evidence that UVA (the light rays emitted by tanning salons) causes skin cancer, in particular, melanoma and premature aging.

Many subsequent studies assessing the role of vitamin D in “protecting” against internal cancer have conflicting results and it will take many years with long-term prospective studies to know for sure. As well, there is controversy regarding the extent, if any, of significant vitamin D deficiency in Americans. Nonetheless, you can obtain vitamin D from diet (e.g. salmon, fortified milk and orange juice) without subjecting yourself to the risk of sun exposure. The National Institutes of Health claims it doesn’t take much sunlight to make adequate vitamin D-likely as little as 30 minutes twice a week without sunscreen!. Alternatively, simply taking supplemental vitamin D (1,000 IU) if you have had skin cancer, are at risk for skin cancer, or simply want to avoid the unsightly wrinkling and discoloration caused by habitual sun exposure is a much safer way to assure adequate levels. My closing recommendation is moderation and see your dermatologist annually!

Article by: Neil Alan Fenske, MD. Professor and Chairman of the Department of Dermatology and Cutaneous Surgery at the University of South Florida