Vitamin D deficiency is associated with an increased risk of developing bladder cancer, according to a systematic review of seven studies presented at the Society for Endocrinology annual conference in Brighton, England. The study adds to a growing body of evidence on the importance of maintaining adequate vitamin D levels.In countries with low levels of sunlight, it is difficult to obtain enough vitamin D from food alone. In the United Kingdom, for example, one in five adults is vitamin D–deficient and three in five have low levels of it. Researchers from the University of Warwick reviewed seven studies on the topic, which ranged from having 112 to 1,125 participants each. Five out of the seven studies linked low vitamin D levels to an increased risk of bladder cancer.