Insufficient sunlight exposure The sunshine vitamin can be produced by the body itself through direct sunlight on the skin. However, in many European countries an insufficient supply of vitamin D3 can be observed. Vitamin D contributes to the mineralization of bones and teeth, supports the normal absorption/utilization of calcium and phosphorus, and maintains normal blood calcium levels. It contributes to the maintenance of normal bones and teeth and muscle function. Vitamin D contributes to the normal function of the immune system and plays a role in cell division.