The big and almighty vitamin D

Sometime in ancient times, thirty or forty years ago, vitamin D was mentioned on several occasions. Young mothers in conversations about their babies, asking how many drops the pediatrician prescribed and vacationers in the summer.

In our times, vitamin D is given much more attention and the reason for this is quite serious. Such attention is due to the almost three-year struggle with the consequences of COVID-19. What does this vitamin have to do with babies, the sun, respiratory diseases, and many more interesting and important things? Secrets and secrets are revealed by Galina Krinskaya , cosmetologist, clinical pharmacologist, brand trainer for PBSerum / IBSA / BioRePeelCl 3. ( Photo by Michele Blackwell on Unsplash.)

Functions of Vitamin D

Vitamins of group D (calciferols) are biologically active fat-soluble substances. The main representatives are ergocalciferol and cholecalciferol, also sitocalciferol, 2,2-dihydroergocalciferol, sigma-calciferol. Cholecalciferol (D3) is synthesized in the epidermis of the skin under ultraviolet irradiation of the B range (with a wavelength of 290-315 nm) from 7-dehydrocholesterol. Ergocalciferol (D2) enters the body exclusively with food, its main sources are liver, yeast, butter, cream, sour cream, egg yolk, cod liver, fatty fish, fish oil.

From a chemical point of view, ergocalciferol differs from cholecalciferol by the presence of a double bond between C22 and C23 and a methyl group at C24 in the molecule.

Metabolically, plasma vitamins D2 and D3 are combined with vitamin D-binding protein (VDBP) and transported to the liver. Here they are hydroxylated and act as the main form of storage. Subsequently, 25-hydroxyvitamin D is transported by a transport protein to the kidneys, where it is hydroxylated again. The hydroxylation reaction in the kidneys is stimulated by parathormone, prolactin, growth hormone and suppressed by high concentrations of phosphate and calcium. The result of these transformations is the active form of the vitamin - 1,25-dihydroxycholecalciferol, or calcitriol.

The most studied and known are the following functions.

1. An increase in the concentration of calcium and phosphate in the blood plasma. To do this, calcitriol induces the synthesis of calcium-binding protein and Ca2+-ATPase components in target cells. As a result:

• increases the absorption of Ca2+ ions in the small intestine;
• stimulates the reabsorption of Ca2+ ions and phosphate ions in the proximal renal tubules.

2. Inhibits the secretion of parathyroid hormone due to an increase in the concentration of calcium in the blood, but enhances its effect on calcium reabsorption in the kidneys.

3. In bone tissue, the role of vitamin D is twofold:

• stimulates the mobilization of Ca2+ ions from bone tissue, as it promotes the differentiation of monocytes and macrophages in the osteoclast, the destruction of the bone matrix, and a decrease in the synthesis of type 1 collagen by osteoblasts;
• increases the mineralization of the bone matrix, since it increases the production of citric acid, which forms insoluble salts with calcium here.

4. In addition, vitamin D, affecting the work of about 200 genes, is involved in the proliferation and differentiation of cells of all organs and tissues, including blood cells and immunocompetent cells. Vitamin D regulates immunogenesis and immune response, stimulates the production of endogenous antimicrobial peptides in the epithelium and phagocytes, limits inflammatory processes by regulating the production of cytokines.

Vitamin D and babies

The best-known, classic manifestation of vitamin D deficiency is rickets, which develops in children between 2 and 24 months of age. With rickets, despite being ingested with food, calcium is not absorbed in the intestines, but is lost in the kidneys, which leads to a decrease in the concentration of calcium in the blood plasma, a violation of the mineralization of bone tissue and, as a result, to osteomalacia (softening of the bones). Osteomalacia is manifested by deformation of the bones of the skull, chest, curvature of the legs, rickety "rosary" on the ribs, an increase in the abdomen due to muscle hypotension, teething and overgrowth of fontanelles slows down.

Vitamin D and the sun

Exposure to UV radiation to redness of the skin at a minimum erythemal dose for 15-20 minutes, depending on skin type, can induce vitamin D production up to 250 μg (1000 IU). However, the conversion of provitamin D3 to the inactive metabolites lumisterol and tachisterol balances the skin biosynthesis of vitamin D3 by a feedback mechanism. This mechanism effectively prevents an overdose of vitamin D3. Shade and cloudy weather can reduce vitamin D production by up to 60%.

There is an opinion that in the case when a person's shadow is longer than his height, then the synthesis of vitamin D almost does not occur. On average, on a summer day, a person, being under the sun, but not burning, produces 10,000-25,000 units of vitamin D. Ultraviolet, necessary for the production of vitamin D, does not penetrate through glass, clothes and cream with SPF protection.

Vitamin D is produced in the summer, slightly - in late spring and early autumn, from about 10 am to 3 pm. In winter we spend what we accumulated in summer. Open faces and arms are not enough space, it would be nice to open the legs and torso, but they are hidden under clothes almost always, except for the beach. We are spending more and more time indoors. People with dark skin produce 6-8 times less vitamin D. Also at risk for vitamin D deficiency are overweight people. 71% of obese men and 62% of women are deficient in vitamin D (less than 75 nmol/l). Vitamin D is fat-soluble, it accumulates in excess fatty subcutaneous tissue and is inaccessible. In a normal weight woman, 35% of vitamin D is distributed in adipose tissue, 30% in blood serum, 20% in muscles, and 15% in other tissues. Overweight women retain three-quarters of their accumulations in adipose tissue. Remember that we synthesize 90% of vitamin D with the help of UV rays, and this compound is more stable, and only 10% we can get from food. The sun is free, and moderate and safe intake can provide adequate levels of vitamin D.

Vitamin D and immunity

In addition to the known effect on bone metabolism, vitamin D is involved in a number of processes in the human body, including the regulation of immune responses. The action of vitamin D occurs through a membrane receptor, which is found in cells of various organs and tissues, in most cells of the immune system and epithelial cells of the mucous membranes. Vitamin D attenuates antigen presentation by dendritic cells, inhibits Th1-cell differentiation and production of Th1-cytokines, shifts the balance of Th1-/Th2-cell responses towards the Th2-response, has an inhibitory effect on Th17 cells, promotes the development of Treg cells and increase their activity . .

Vitamin D enhances the production of "endogenous" antibiotics that have a great effect on bacteria, viruses and fungi. Studies show that vitamin D is extremely important for the prevention of autoimmune and atopic diseases: multiple sclerosis, rheumatoid arthritis, insulin-dependent diabetes, Crohn's disease, ulcerative colitis, asthma; chronic obstructive pulmonary disease, arterial hypertension, atherosclerosis, osteoporosis, prevents the development of tumor processes, facilitates the course of respiratory infections. Since latent and undiagnosed hypovitaminosis D is present in almost half of the population of our planet, there is a need for further research and a wide range of measures for the prevention and treatment of vitamin D-deficiency conditions.

Hypovitaminosis D

Hypovitaminosis D is characterized by such signs as:

• weakened immunity and low energy levels;
• sleep disturbance;
• fragile teeth and bones;
• decreased libido due to lower testosterone levels;
• muscle weakness;
• insulin resistance;
• muscle and bone pain of unknown origin;
• poor wound healing.

Acquired hypovitaminosis often occurs with nutritional deficiencies (vegetarianism), and the cause may also be a decrease in hydroxylation of calciferol in diseases of the liver and kidneys, indigestion and lipid absorption in celiac disease and cholestasis.

Hypervitaminosis D

Excessive intake of vitamin D with drugs has side effects such as:

• nausea;
• headache;
• loss of appetite and weight;
• polyuria, thirst, polydipsia;
• constipation;
• hypertension;
• muscle rigidity.

Chronic hypervitaminosis leads to bone demineralization, which in turn provokes fragility and fractures, and an increase in the concentration of calcium and phosphorus ions in the blood leads to calcification of blood vessels, lung tissue and kidneys.

Vitamin D Requirements

Requirements can be measured both in micrograms and in international units (IU), 25 micrograms correspond to 1000 IU.

Physiological daily requirement:

• for young children - 10 mcg, or 400 IU;
• for older children and adults - 10-20 mcg, or 400-800 IU;
• for people over the age of 60 - 15 mcg, or 600 IU.

The upper tolerable intake level is 50 micrograms per day. Dietary Guidelines for Americans (USA) recommended daily allowances: children and adults from 0 to 70 years old inclusive - 15 mcg, starting from 71 years old - 20 mcg.

The most informative method for measuring vitamin D levels is "25(OH) vitamin D". Despite the generally accepted range of 30-100 ng/ml, the optimal values are at the level of 60-80 ng/ml or 150-200 nmol/l. The number 30 is introduced to prevent rickets or osteoporosis, but does not take into account other disorders in the body caused by low levels of vitamin D. High doses of vitamin D (from 2000 to 6000 IU) are used mainly to quickly raise vitamin D levels and at least it has been verified Despite the fact that such doses are well tolerated and without consequences, there is evidence that ultra-high levels of vitamin D can lead to certain problems.

What should we do, victims of modern civilization, employed at work in enclosed spaces, those who travel by car instead of walking, those who get tired after work and consider sitting or lying on the couch the best rest, those who are looking for cheap dopamine or for saving time eating fast food or prioritizing fast carbs? The recipes are quite simple - the food is complete and proper, like the Mediterranean diet. Spend your free time on the move and sunbathe properly. If there is a risk of vitamin D hypovitaminosis (and every second person has it), take dietary supplements, having first consulted a doctor and the results of a laboratory test.

Remember that prevention is always better than cure, moderation and moderation is always the best recommendation, and interest in one's own health is the highest priority.

Source: PRO Cosmetology magazine by Cosmetologist #1, 2022