Cancer preventer. Vitamin D serves as a precursor to the hormone calcitriol, which regulates cell differentiation and helps prevent cancer. More than 60 studies have linked adequate vitamin D levels to a lower risk of various cancers. Vitamin D deficiency often precedes breast cancer and presages more aggressive forms of the disease. High vitamin D levels may improve survival among people with cancer, and two studies found that high levels of vitamin D reduced the risk of death from breast cancer by almost 50 percent. In men, high vitamin D levels at the time of prostate cancer diagnosis are associated with longer survival.
Dose: 5,000 to 10,000 IU daily