Vitamin D (cholecalciferol) has a key function for health. It is involved in thousands of regulatory processes in the human body cells. As a result, a vitamin D deficiency increases the risk of disease considerably - especially in winter, when the sun is far too low in the northern regions of the world to provide the necessary UV radiation.

 But it is precisely this UV radiation that the body is dependent on, because around 90 percent of vitamin D is formed in the skin and converted into the most effective form of vitamin D in the body in the liver and kidneys. 
 
 Vitamin D is of great importance for strong defences, bones and teeth. 
 
 Vitamin D controls the calcium and phosphate balance as well as the citric acid metabolism. Calcium and phosphate absorption in the intestine is promoted by vitamin D and calcium excretion via the kidneys is reduced. This and the increased calcium incorporation into the bones are necessary for bone formation. Vitamin D deficiency leads to reduced bone hardness. 
 
 To prevent a vitamin D deficiency, a supply of vitamin D3 preparations is therefore recommended by all experts.