Vitamin D and Nonmelanoma Skin Cancer Linked? One Study
High normal levels of vitamin D have been associated with an increased risk of nonmelanoma skin cancer (NMSC) in one new study. This finding adds to the confusion regarding the relationship between skin cancer and vitamin D, and the study’s authors note that increased sunlight exposure and other factors likely complicate the issue.
Skin cancer is a challenge to understand
The studies regarding the relationship between vitamin D and skin cancer is indeed confusing: some studies have indicated that the nutrient may reduce the risk of the disease, while others have suggested it may increase the risk. Research concerning the benefits of vitamin D for other health issues, ranging from osteoporosis to depression, arthritis, and Parkinson’s disease, among others, have been promising.
This latest study involved data collected over an average of 9.8 years from 3,223 white men and women who were members of an HMO. All the participants had a high probability of developing nonmelanoma skin cancer, which includes basal cell cancer and squamous cell cancer. Nonmelanoma skin cancer is the most common type of skin cancer and can be cured when it is found early and treated.
The study’s participants had their vitamin D levels (serum 25 (OH)D) taken as part of their evaluation for osteoporosis or low bone density, and the investigators used these data to track cases of nonmelanoma skin cancer. Only one measurement was obtained from each participant.
Of the 3,233 individuals, 2,257 had serum 25(OH)D levels deemed insufficient, where 30 nanograms per milliliter (30 ng/mL) was defined as a sufficient levels of vitamin D. Of this group, 240 patients developed nonmelanoma skin cancer: 163 had basal cell carcinoma, 49 had squamous cell carcinoma, and 28 had both forms of the disease. Eighty percent of the cancers developed in areas that had been frequently exposed to sunlight.
When the researchers categorized the patients based on their 25(OH)D levels, individuals with the highest levels of vitamin D (31 ng/mL or greater) had a 60 percent greater risk of developing nonmelanoma skin cancer than did patients with the lowest levels (less than 19 ng/mL). The association between higher 25 (OH)D levels and nonmelanoma skin cancer on areas with less exposure to ultraviolet rays was not statistically significant.
Debate over what constitutes a sufficient serum level of vitamin D has been ongoing. The Food and Nutrition Board recommends children and adults consume 600 International Units (IUs) daily to achieve at least 20 ng/mL, which it deems adequate for bone and overall health in healthy individuals. The Vitamin D Council notes that 50 to 80 ng/mL is recommended and that healthy adolescents and adults need 5,000 IU daily.
According to study authors Melody Eide, MD, and her colleagues at Henry Ford Hospital in Detroit, their findings add “to the limited and conflicting epidemiological investigation regarding the relationship between vitamin D and [nonmelanoma skin cancer].” They also stress that “the direct relationship of UV exposure with both vitamin D and NMSC makes it a likely profound confounder in this, and other, studies.”
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