Vitamin D is hormone the body produces through sun exposure. Most adults don’t get enough of it, but research suggests that D helps protect against serious diseases. One example, is breast cancer, in which it curbs abnormal cell growth and the formation of blood vessels that feed tumors. Adequate levels at the time of diagnosis could affect prognosis and alter the disease’s course, potentially reducing the risk of recurrence, spread and death.
To get a safe amount of sun, estimate how long it would take for your skin to tan slightly. Reduce that time by half if you have fair-skin or one-quarter if you’re darker, and try to get that much exposure a few days a week. I also recommend that everyone take at least 2,000 IU of Ds daily, and more if blood tests show you’re low.
Source: Prevention Magazine October 2014 by Dr. Andrew Weil The Integrative MD