Vitamin D is essential for many skeletal and extra-skeletal functions of the body, with D3 (cholecalciferol) being its most bioavailable form. Specifically, D has an effect on various processes such as: • the smooth absorption of phosphorus and calcium and the maintenance of smooth calcium levels in the blood • the maintenance of healthy bones, muscles, teeth • cell division • the function of the thyroid and parathyroid glands • the normal function of the nervous system • the normal function of the immune system