Studies show that increased levels of vitamin D-3 reduce the risk of breast and colorectal cancers and protect against cardiovascular disease. Vitamin D-3's immune-modulating effect fights infections of viral, bacterial and fungal origin. The median intake of D-3 in the U.S. is 230 IU/day, which is far below the levels needed for protection. Our Vitamin D-3, cholecalciferol, is the most active form of vitamin D and is equivalent to the vitamin D formed on our skin from ultraviolet B light.