Made by the body when the skin is exposed to sunlight. Research has shown that Vitamin D3 plays an important role in regulating mood, warding off depression, and facilitating normal immune system function. It helps the body use calcium from the diet. Symptoms of bone pain and muscle weakness can mean deficiency. Perhaps the most vital are regulating the absorption of calcium and phosphorus, Research suggests that vitamin D3 could play a role in the prevention and treatment of a number of different conditions, including type1 and type 2 diabetes, hypertension, glucose intolerance, and multiple sclerosis.