Vitamin D might not help prevent cancer, but it does help lower the risk of dying from it, according to a study from Harvard School of Public Health. In this meta-analysis of randomized, controlled trials looking at vitamin D supplementation and cancer incidence and mortality, researchers found that taking vitamin D supplements at a level of 400IU to 1,000IU a day for two to seven years did not protect against the development of cancer. However, vitamin D supplementation did lower the risk of dying from cancer by 12%.
Kerum N, Giovannucci E: Vitamin D supplementation and cancer incidence and mortality. British Journal of Cancer 2014;June 10th.