DOUBLEHERZ Vitamin D3 2000 IU tablets If the bodys own production of vitamin D is insufficient or absent, an increased intake of vitamin D through food becomes necessary. Nevertheless, many people still do not consume enough vitamin D through their diet. Vitamin D plays an important role in cell division and maintaining a normal immune system. It also supports the maintenance of healthy bones and teeth. Therefore, vitamin D fulfills a central function in the body, especially during times of increased need and when the bodys own production is insufficient.