Low exposure to ultraviolet-B (UV-B) radiation from sunlight, which results in a defective synthesis of vitamin D, have been suggested to increase the risk for developing MS. However, it remains a matter of debate whether sunlight and vitamin D levels also influence disease severity and progression. In this study, researchers in Germany assessed the impact of two independent measures of sunlight exposure — vitamin D levels and latitude — on MS disease severity. (Decreasing latitude is linked with an increase of sunlight that reaches the Earth’s surface.) Also, they assessed whether the effects of sunlight exposure were modulated by medication or variations in the gene coding for the melanocortin 1 receptor (