Oct. 18, 2010 -- Protecting your skin from the sun to help prevent skin cancer may have an unhealthy side effect: vitamin D deficiency.

A new study shows vitamin D deficiency is increasingly common among people with a genetic predisposition to sun-related skin cancers known as basal cell nevus syndrome.

Researchers found people with basal cell nevus syndrome were three times more likely to have low vitamin D levels than the general population.

“Vitamin D deficiency has been associated with an increased risk of autoimmune disease, fractures, cancer, cardiovascular disease and all-cause mortality,” write researcher Jean Y. Tang, MD, PhD of Stanford University, and colleagues in the Archives of Dermatology. “There is increasing concern that sun protection, recommended by dermatologists to prevent further UV damage in populations susceptible to skin cancer, may result in abnormally low levels of [vitamin D], which may have subsequent detrimental effects on health.”

In the study, researchers took periodic blood samples from 41 people with basal cell nevus syndrome over a period of two years. The results show 23 (56%) of the participants had vitamin D deficiency. 

Blood levels of vitamin D were lower among those with basal cell nevus syndrome who were overweight and in those who had blood samples taken in winter compared with summer.

Amazing Vitamin D, Nutrition's Newest Star
Reducing Sun Exposure

People with basal cell nevus syndrome tend to develop multiple cancerous lesions in early adulthood. As a result, they are advised to take steps to reduce their sun exposure and skin cancer risk by using sunscreen and avoiding the sun during peak hours.

Sunlight is the best source of vitamin D, but it is also found in fortified milk, butter, eggs, fish liver oils, and supplements.

Researchers say it's not surprising to find high levels of vitamin D deficiency in people at risk for skin cancer, but the magnitude of the problem was unexpected. The results suggest vitamin D supplementation may be recommended for people with basal cell nevus syndrome.

The researchers also suggest that further studies are needed to determine the optimal amount of vitamin D supplementation needed for preventing deficiency in people in the general population using sunscreen and other methods of sun protection.