US Pharm. 2011;36(9):HS-39-HS-40. 

In a cohort study, researchers reported that higher levels of vitamin D, although within a normal range, are linked to an increased risk of nonmelanoma skin cancer. People with higher serum 25-hydroxyvitamin D (25(OH)D) were more likely to develop squamous cell or basal cell carcinoma, according to Melody Eide, MD, and colleagues at Henry Ford Hospital in Detroit, Michigan.  

Ultraviolet B light is known to cause skin cancer, but it also increases cutaneous vitamin D synthesis, the researchers noted, adding that the relationship between vitamin D and skin cancer is complex and studies have yielded conflicting results. Increased exposure to sunlight, along with other factors, probably complicates the relationship, Dr. Eide and colleagues reported online in Archives of Dermatology.