The functions and modes of action of vitamin D
Cholecalciferol (vitamin D) is found in all non-plant eukaryotes, living organisms with a nucleus in their cells. Animals and humans possess it. Its designation as a vitamin leads to misunderstanding, since vitamin D exerts the action of a prohormone in the human body. It is formed from 7-dehydrocholesterol when exposed to ultraviolet light. Via an intermediate stage, it is transformed into the hormone calcitriol.
Function and effect of vitamin D in the body
After its formation by ultraviolet light, the blood transports vitamin D and its binding protein to the liver. In the cells of the liver, the enzyme cytochrome P450 2R1 transforms it into calcidiol, a storage form of vitamin D.
Bound to a protein, it recirculates in the blood for about 19 days. The storage form of vitamin D proves necessary because the body does not absorb light continuously. Via the blood, vitamin D in its storage form calcidiol reaches the target tissue, such as the kidneys.
There it is activated to form calcitriol. Only calcitriol triggers the necessary reactions of the vitamin D receptors. Activation in the kidneys depends on the factors parathyroid hormone, calcium and phosphate levels. If the parathyroid hormone level increases and calcium and phosphate levels decrease, activation of calcitriol occurs.
Regulators serve to produce just enough vitamin D to stimulate the body to synthesize calcium and phosphate. In other target tissues, factors such as cytokines or growth hormones regulate the production of calcitriol. The vitamin D action in the cells of the target organs is that of a steroid hormone. Binding of the vitamin D receptor occurs. In the nucleus, this alters the transcription of various genes that respond to hormones. This causes a change in the production of proteins.
Long-term effect of vitamin D in the body
Vitamin D is therefore much more like a differentiation hormone than a vitamin. The body converts it into a hormone that regulates cell growth and strengthens bones. It also prevents the proliferation of diseased cells, which may become malignant. Studies show that vitamin D has an effect that significantly reduces the risk of different types of cancer, such as colon cancer.
Most body tissues not only have the capacity to recognize vitamin D, but also to produce it. This leads to the conclusion that vitamin D is a key hormone that protects the body. Clinical studies illustrate that vitamin D has the effect of positively influencing chronic diseases. It strengthens the immune system not least in type I diabetes, multiple sclerosis and rheumatoid arthritis.
Vitamin D also has a protective effect on many tissues against aging processes. It protects the skin from UV-induced damage. Vitamin D is a promising substance for natural anti-aging medicine. All body tissues have vitamin D receptors. This results in a need for every tissue to have vitamin D in order to function optimally.
The vitamin D effect does not only unfold in cancer. Vitamin D also protects against high blood pressure and heart disease. The cardiac death rate, which increases in winter compared to sunny days, serves as an indication of the protective function in heart disease.
Studies on the effect of vitamin D
Vitamin D also has an effect with regard to the brain. In particular, the brain of older people benefits from the intake of vitamin D. This conclusion allows a paper by researchers from the University of Manchester in the Journal of Neurology, Neurosurgery and Psychiatry. They studied 3,000 men aged 40 to 79 in a Europe-wide study.
They conducted a series of cognitive tests with the participants. Trial participants who had more vitamin D in their blood performed better in the areas of memory, attention and processing speed. The effect was more noticeable with increasing age. In their calculations, the researchers took into account factors influencing the results, such as the amount of physical exercise, depression and the time of year.
The study found a correlation between vitamin D and higher cognitive abilities. The exact biological background still needs to be investigated. Vitamin D may protect the nerves or regulate the production of neurotransmitters. The long-term effects of vitamin D are consistently positive. Vitamin D protects the heart and brain and curbs malignant growths. It also strengthens the immune system. Especially in the case of chronic diseases, physicians advise the intake of vitamin D.