Bluebonnet Nutrition Vitamin D3 provides natural vitamin D3 (cholecalciferol) from Lanolin. Vitamin D3 helps regulate and control the metabolism of calcium and phosphorus by aiding in the absorption of these two minerals from the small intestine. It also directly affects the rate at which these minerals form and maintain bone. Vitamin D3 is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is essential for promoting calcium absorption in the stomach and maintaining adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and stop hypocalcemic tetany. Vitamin D3 is also necessary to help support strong teeth and bones.