Excessive sun exposure can bring with it life-threatening diseases, particularly skin cancer–but a growing fear of skin cancer may lead to vitamin D deficiency in overprotective patients or those who spend too much time indoors.

The dichotomous impact of sun exposure has become a focus of research for dermatologists at Stanford. This month’s Archives of Dermatology published a research study conducted by assistant professor of dermatology Jean Tang M.D. Ph.D. ’03 on correlations between vitamin D deficiency and a rare form of skin cancer called basal cell nevus syndrome (BCNS).

Children’s Hospital Oakland Research Institute scientist Ervin Epstein and Stanford Hospital resident Eleni Linos also joined Tang in completing the study, which examined the blood of 41 patients with BCNS to determine vitamin D levels. The results showed that patients with skin cancer were three times more likely to be vitamin D deficient than the normal population.

Tang and fellow researchers concluded increased attention to sun protection among skin cancer patients is causing the rises in vitamin D deficiency.

“Our study shows that skin cancer patients who vigilantly photoprotect are three times at risk for vitamin D deficiency,” Tang said.

In order to prevent skin cancer, many dermatologists recommend refraining from unnecessary sun exposure. According to Tang, though, such recommendations may have adverse effects by reducing the amount of vitamin D that skin can produce. Vitamin D facilitates the absorption of calcium and also prevents a number of diseases, including cancers, heart disease and autoimmune disease.

“For dermatologists, our study highlights the fact that avoiding excessive sun exposure is important for decreasing your risk for skin cancer,” Tang noted. “But for some of our patients, especially if they’re frail, especially if they have osteoporosis, especially if they have fractures, dermatologists should be monitoring their vitamin D levels.”

Epstein emphasized the need to compensate for the decreased rates of vitamin D generation, particularly exhorting dermatologists to pay close attention to vitamin D in their patients.

“We, as dermatologists, are telling all of our patients to avoid sunlight to reduce the incidence of skin cancer,” Epstein said. “The moral of the story is that dermatologists ought to be telling patients to take supplemental oral vitamin D.”

Skin cancer only constituted one of the conditions that correlate with vitamin D deficiency. Tang’s study also found other risk factors that may lead to vitamin D deficiency, including obesity.

“Right now, we don’t know for sure the importance of vitamin D in preventing cardiovascular disease or cancer, but vitamin D has gotten a lot of press because there’s been suggestive evidence that it could be important in prevention of these diseases and more and more people are becoming vitamin D deficient,” Tang said. “And that is probably related to obesity and a more indoor lifestyle.”

Tang’s study had many unique elements not found in previous studies on skin cancer and vitamin D deficiency. In particular, previous studies didn’t look at BCNS and used fewer subjects. Tang also stressed that her study utilized well-developed match control to account for all factors in skin cancer and vitamin D deficiency.

At Stanford, several dermatological studies are arising as a result of Tang’s research. Linos is working on an offshoot study on differences between sun protection methods, while Stanford Hospital resident Ashley Wysong and the Department of Dermatology are working with Stanford athletes to study sun protection among athletes.

While these studies in sun exposure provide valuable information for dermatologists regarding the effects of sun on the body, Epstein emphasizes that patients must also be aware of the repercussions of medical advice.

“I think it’s a reminder that medical interventions may have both positive and negative effects,” Epstein cautioned. “We’re trying to protect people from having skin cancer, yet we may be reducing vitamin D levels.”

Epstein ultimately encourages medical consumers to consider all facets of medical advice. “If you understand what you’re doing, hopefully you can take a double-edged sword and turn it into all good,” he said.