The effect of vitamin D supplementation on risk of keratinocyte cancer: an exploratory analysis of the D-Health randomized controlled trial.

Vitamin D supplementation did not reduce the incidence of KC or other actinic lesions. What is already known about this topic? Laboratory studies have suggested possible protective effects of vitamin D on skin cancer. Observational studies investigating the association between vitamin D and risk of keratinocyte cancer are largely uninformative as ultraviolet radiation both causes skin cancer and is the primary source of vitamin D. The evidence from randomized controlled trials of vitamin D is limited and inconclusive. What does this study add? This population-based, randomized controlled trial suggests that supplementing older adults with a high monthly dose of vitamin D for 5 years does not affect the incidence of keratinocyte cancer.