Vitamin D belongs to the group of fat-soluble vitamins. It functions as a prohormone in the body and must first be converted into its active form, vitamin D3 (cholecalciferol), in the liver and especially in the kidneys in order to be able to act as a hormone. Vitamin D is absorbed through food on the one hand. On the other hand, it can also be produced in the body with the help of ultraviolet radiation from the short-wave portion of solar radiation. This process is known as endogenous synthesis.
As one of the most important vitamins for calcium metabolism, the "sunshine vitamin" plays a crucial role in bone structure and tooth development. Vitamin D3 improves the absorption of calcium and phosphate from the intestines. Vitamin D3 also increases bone mineralization and increases the reabsorption of calcium in the kidneys.
In addition, vitamin D3 is of great importance for the stability of our immune system. A sufficiently high vitamin D3 level is, among other things, a prerequisite for an appropriate cellular immune response in the event of an infection with viruses, fungi or bacteria and for the body to be able to mobilize defense cells against invading pathogens.
Especially during the cold season, the "sun hormone" is one of the essential vitamins for our health. During the cold season, the body often does not have the ability to synthesize sufficient amounts of vitamin D3 from solar radiation. Even when the sun shines, it is too low in the winter to provide the skin with sufficient ultraviolet radiation. Although a healthy person can survive for a while on vitamin D reserves in their fatty tissue, deficiency symptoms often occur, particularly at the end of the dark season. Therefore, taking vitamin D3 as a dietary supplement can be useful during this period.