The body produces vitamin D when the skin is exposed to sunlight.  The vitamin is also found naturally in some foods, such as fatty fish and mushrooms, and is often added to others, including milk and some cereals.  For people with known vitamin D deficiencies, supplementation is recommended to maintain bone health and prevent fractures.  VITAL called the vitamin D and Omega-3 Trial, main goal was to see if there’s benefit to getting above the recommended dietary allowance, more than what is considered necessary for bone health,” explained JoAnn Manson, M.D., of Brigham and Women’s Hospital and Harvard Medical School, who led the study.  VITAL was designed so that it could study the effects of both vitamin D and omega-3 supplements.  The trial’s primary endpoints–the key outcomes it measured–were the supplements impact on the risk of developing cancer and heart disease.  It also had several secondary endpoints, including the risk of dying from cancer.  VITAL was funded primarily by NCI and the National Heart, Lung, and Blood Institute.

Source:  NCI