In this study, the authors examined data from experiments on vitamin D ^[1]. Data from in-vitro experiments suggest vitamin D reduces the rate of skin aging whereas population studies suggest the opposite, most likely due to confounding by UV-exposure. The authors investigated whether there are causal associations between 25-hydroxyvitamin D concentrations and features of skin aging in a bidirectional Mendelian Randomization Study. Facial skin aging features (perceived age, wrinkling, pigmented spots) were assessed either manually or digitally. Associations between 25-hydroxyvitamin D and skin aging features were tested.The authors observed that higher serum 25-hydroxyvitamin D was associated with a higher perceived age, more skin wrinkling, but not with more pigmented spots. In contrast, genetically determined 25-hydroxyvitamin D concentration was not associated with any skin aging. They conclude that the study did not indicate that associations between 25-hydroxyvitamin D and features of skin aging are causal.