Vitamin D is best known for its role in aiding the absorption of calcium from the digestive system and promoting bone formation but it has many other actions including balancing immune function and supporting mood. Vitamin D is synthesized by the skin following exposure to ultraviolet rays from sunlight but many people do not spend enough time outdoors and become deficient in this essential vitamin. Vitamin D deficiency has been linked to numerous health conditions including osteoporosis rickets autoimmune conditions diabetes SAD (seasonal affective disorder) chronic pain and frequent infections. There is an obvious need to supplement with extra vitamin D especially in the elderly and children during the winter and for people with chronic diseases.