D as in Dating the sun
Every day, you feel beneficial effects of energy of radiation sent by the sun. Our bodies have adapted so well to it that they simply desire moderate doses of this radiation. One of beneficial effects of sun energy is the production of vitamin D in the skin.
Vitamins from D group are called calciferols. They are formed in the reproductive layer of endothelium from provitamins (ergosterol and cholesterol derivative) under the influence of UVB radiation, 290-310 nm. Unfortunately, they are not formed after a visit in a solarium because lamps used in such places usually emit UVA radiation above 290-310 nm.
D as in Dense bones
All mothers certainly remember that children must spend a lot of time outdoors and that the sun is essential to avoid rickets. This does not change when we are adults. The sun is still necessary to produce the essential vitamin D3 in adults.
Calciferols in bones maintain the homeostasis of calcium and phosphorus and take part in the mineralization and reconstruction of the osseous tissue. The most active substance from the group of vitamins D in these processes is vitamin D3.
Vitamin D3 increases the efficiency of assimilating calcium and phosphates in the intestines, ensures their appropriate levels in the blood circulation system, and activates the production collagen by osteoblasts (bone-forming cells).
However, the role of the builder of bones and teeth is not all. Vitamin D3, or rather its active part called calcitriol, also regulates hormones secretion and is necessary for correct activity of the thyroid.
Calcitriol is a hormone which controls calcium-phosphate management of the body, taking care mainly of the bone system. Its antagonist is parathormone produced by parathyroid glands. Parathormone also controls calcium levels, but mainly in blood serum.
The cooperation of both these hormones decides about the condition of bones and the quantity of calcium in the body outside the bone system.
Parathormone increases calcium levels in blood and calcitriol reduces calcium levels in blood serum. Parathormone absorbs calcium from bones to blood and calcitriol absorbs calcium from blood and retains it in bones. A disturbed balance in this cooperation may result in excessive activity of parathyroid glands and, as a consequence, a disturbed activity of thyroid.
Lately, scientists have discovered that the immunological system cells (T cells) produce vitamin D3. They also have vitamin D receptors. Receptors are cells which recognize a substance in the environment. That is why we know that vitamin D3 is also necessary in proper immunity. However, the internal production of vitamin D is not always sufficient for providing immunity.
In 2007, based on the analysis of research from many centres, American scientists determined that the supplementation of 2000 units of vitamin D daily eliminated seasonal flu and reduced its range dramatically. Research also confirmed that vitamin D deficiency results in reduced immunity and chronic bacterial and mycotic infections.
The immunity-related function of vitamin D consists in the indirect anti-bacterial activity and the regulation of immunity.
According to scientists, vitamin D activates genes related to anti-bacterial proteins which act like natural antibiotics, e.g. proteins fighting tuberculosis. These anti-bacterial proteins are produced by immunological cells upon the contact with bacterial cell membranes in the presence of the active form of vitamin D3, i.e. calcitriol.
D as in Dopamine
Under the influence of sun rays, melanins are formed in the skin, which protect deeper skin layers from too aggressive radiation. This is a group of pigments; two of them are dyes colouring the skin and hair and one, neuromelanin, is a derivative of dopamine neurotransmitter, which is responsible for feeling happiness. Perhaps this is the reason for the universal feeling of happiness because of the sun.
To fight with tumour
In some tumours (breast, prostate, or large intestine tumours), vitamin D prevents cell multiplication. Some results of clinical and epidemiological research confirm that sufficiently high vitamin D levels in the body may reduce the risk of tumours.
How and how much to take?
Effective production of vitamin D3 in our weather conditions is possible mainly in summer for almost the whole daytime; in March and September it is possible only for about 3 hours around noon.
The dose resulting in a slight reddening (exposure of 18% of the body surface) makes the skin synthetize app. 10,000 units (IU) of vitamin D. The daily demand of an adult is 400 units (10 mcg); for children and young people with deficiencies it can be even up to 1,000 units.
When the production of vitamin D in skin is not sufficient due to our weather conditions, air pollution, using sun blocks, and skin ageing, this vitamins should be supplied with food or supplements in the form of pharmaceuticals.
Sources of vitamin D include tran oil (fish oil), liver, and egg yolks. Pharmaceuticals should contain cholecalcyferol, i.e. vitamin D3, which is more efficient and permanent than D2. Vitamin D taken in pharmaceuticals may not be applied in large doses because excessive amounts are toxic.
However, it is not possible for the sun to produce excessive amounts of vitamin D. There is never too much of it!