Fat-soluble Vitamins: Nature And Representatives

Fat-soluble vitamins: nature and representatives

This group of organic compounds of a lipophilic nature, which ensures their free penetration through the lipid layer of the membrane directly into the cell, includes four vitamins, each of which regulates a kind of orchestra of physical and physico-chemical effects and interactions:

• Vitamin A - has several biologically active forms: retinol, retinal, retinoic acid - the latter, by the way, is responsible for the growth and differentiation of both embryonic cells and those that are part of the bone, cartilage and epithelial tissue of an adult organism - hence its second The name is Vitamin Growth.

• Vitamin D or cholecalciferol - provides, along with the hormones of the thyroid and parathyroid glands, the regulation of phosphorus-calcium metabolism, and also has a significant effect on the functioning of the immune system, the secretion of insulin by beta cells of the pancreatic islets and blood pressure (by inhibiting renin, which is responsible for its increase) .

   

• Vitamin E is a heterogeneous group of compounds, the main of which, undoubtedly, is alpha-tocopherol, a powerful antioxidant that protects cell membrane lipids from oxidation by free radicals.

• Vitamin K is responsible for blood clotting and bone mineralization.

Antioxidant properties of tocopherols

All this is necessary to create a potential difference: an excess of positively charged protons on the one hand and electrons carrying a negative charge on the other, ultimately stimulates the opening of the “pump” for the production of ATP.

But what happens if, at one of the stages, some of the bouncing “grasshoppers” get lost somewhere – let’s say, because of the not very good work of the nannies looking after them, who at some point safely overlooked and discovered the loss too late? So, in essence, free-radicals are formed: children who escaped from nurses, who lost their arm in another street fight - or, in the language of biochemistry, an electron.

They, like any person, do not really want to exist in such an inferior form - not distinguished by special nobility, these little criminals are eager to take the lost electron from normal cellular structures, thus turning them into free radicals. The shuttle mechanism is no different.

However, the organism, finding benefits everywhere, did not miss the brilliant idea given to it on a golden platter and decided: why not fight the enemies that invaded its territory in this way: various bacteria, fungi and parasites? In particular, he used this mechanism as a factor that kills microbes at one of the stages of phagocytosis, which is a factor of nonspecific protection implemented by cellular immunity. Inside immune-competent cells — neutrophils, for example — that normally lack mitochondria, he created small factories to produce free radicals.

The new weapon was really impressive - more than one military training ground could envy the effectiveness of chemical defense today. However, despite all the thoughtfulness and brilliant execution, accompanying problems also arose: free radicals were able to damage the cells of the macroorganism: they did not have specific receptors for recognizing “us” and “them”: in fact, this is a poorly controlled flock of barbarians who it doesn't matter whose towns and villages to destroy: one's own or the enemy's.

And they, most likely, would have succeeded in finally shifting the balance towards chaos and further dystrophic and necrotic changes accompanying it, if it were not for the existence of police officers-antioxidants that neutralize violators of order in various ways. One of these guardians of homeostasis is tocopherol.

The fact is that in the process of their so-called peroxidation, unsaturated fatty acid is split off from phospholipids, which later goes to the synthesis of such inflammatory mediators as prostaglandins and leukotrienes, which contribute to the expansion of arteries with subsequent plethora and increase vascular permeability, as a result of which edema develops.

The effects of vitamin D

This fat-soluble vitamin is implicitly classified as a hormone - the spectrum of its effects is so extensive. It is formed in our body from cholesterol, undergoing a series of biochemical transformations implemented in the skin, liver and kidneys - and at the initial stages of its synthesis, as you know, ultraviolet is needed. At these stages, as a rule, the first problems begin, leading to such an acute issue of hypovitaminosis, which is widespread everywhere: after all, as the American doctor M. Gregor cleverly noted, people have long ceased to run naked around equatorial Africa.

In addition, it can come from outside - with food (in particular, fatty fish, eggs, dairy products) - this is the so-called D2 or ergocalciferol.

Like steroid hormones, it easily penetrates that insulating cell border that is selectively permeable to some substances and absolutely impregnable to others - the plasma membrane. After such a kind of passport control, which, as a rule, proceeds without any energy consumption - by simple diffusion - vitamin D goes to the very core - to the nucleus and has a modulating effect on more than 2000 genes. Impressive, isn't it?

There is no system of our body that is not directly or indirectly affected by calciferol - let's take a closer look at the most interesting effects that it has on certain organs and tissues.

• Vitamin D and the digestive system

Recent studies show that increasing vitamin D3 intake to 2000 IU/day among the American population reduced the risk of colorectal cancer by 27%. This function is most likely due to the presence of a receptor for this vitamin in epithelial cells - VDR, binding to which it has an antiproliferative effect, and also inhibits angiogenesis - the formation of new blood vessels, which plays a huge role in the mechanisms of antitumor protection.

The localization of VDR (Vitamin D receptor) is not limited to the intestinal mucosa alone - they are “scattered”, literally, in various cells of our body. The liver is no exception, so it is suggested that the polymorphism of these receptors is one of the most predisposing factors in the development of diseases such as primary biliary cirrhosis and autoimmune hepatitis.

• The antitumor activity of calcitriol was studied in a model of prostate cancer - and there, having various biochemical effects, it has established itself as an effective and quite advanced treatment method, or at least an excellent addition to the main therapy.

By activating various signaling pathways, it invariably led to a single result - the death of cancer cells. So, for example, vitamin D suppressed the process of division - mitosis; stimulated apoptosis - programmed cell death - and activated the enzymes that carry out this mechanism - caspases.

In addition, in the context of a malignant tumor of the prostate, it must be added that the main trigger in the pathogenesis of this pathology is an excess of testosterone. Cholecalciferol, acting on key enzymes that metabolize sex hormones (such as some members of the cytochrome P450 family: CYP3A4, CYP3A5, CYP3A43), leads to a decrease in the level of androgens in tumor cells.

• Vitamin D and the reproductive system

Calcitriol has not bypassed the process of fertilization - in particular, it plays an important role in the mechanisms of implantation, that is, attachment to the wall of the uterus of the fetal egg - again, by regulating certain genes responsible for this phenomenon.

Interestingly, the placenta itself actively synthesizes this organic compound - and this, as expected, is involved in the formation of a specific immune response aimed at maintaining pregnancy (after all, the fetus, in fact, should be perceived as foreign, and, therefore, subject to elimination in the name of world order on the streets of our body, object).

Interestingly, according to statistics, more than 85% of patients suffering from such a common gynecological disorder as polycystic ovary syndrome (PCOS) have a low level of vitamin D in the blood serum. In addition, many gynecologists begin to prescribe it, making a similar diagnosis, in combination with calcium and metformin - by the way, foreign doctors have long confirmed in their scientific works a kind of synergism of these drugs, manifested primarily by a decrease in excess body weight, an increase in the sensitivity of receptors to insulin, which occupies a central place on the pedestal in the development of that impressive bouquet of hyperandrogenism that usually accompanies PCOS, as well as a significant decrease in the concentration of testosterone and androstenedione in plasma in the women studied.

• Vitamin D and immunity

The effect of calcitriol on various mechanisms of both cellular and humoral immune defense has been actively studied for decades. So, for example, its antimicrobial protection against the causative agent of tuberculosis - mycobacteria - was the subject of active discussion back in 1940!

Biological supplements with the active form of vitamin D can also be used in addition to the main therapy aimed at the eradication of Helicobacter and the treatment of ulcers of the gastric and duodenal mucosa - and all due to their direct bactericidal action!

The recommended daily allowance, according to American doctors, is 600 IU / day for calciferol, and the acceptable upper intake level is 4000 IU / day.

Importance of Vitamin K

Unfortunately, for a long time it was believed that all the effects of vitamin K are limited to participation in the mechanisms of blood coagulation, and, therefore, in maintaining hemostasis. Indeed, most of the host factors in this rather complex cascade mechanism directly depend on its concentration.

By the way, it is interesting that the two most significant inhibitors of hemocoagulation - proteins C and S are also vitamin K-dependent.

However, it is most correct to single out exactly 2 representatives: vitamin K1 (phylloquinone), which, in fact, regulates hemostasis, and vitamin K2 (menaquinone), which is involved in the control of calcium metabolism.

By the way, it is K2 that is formed by residents of our intestines - representatives of its normal microflora, and also, like K1, can come with food.

It is thanks to vitamin K2 that calcium remains in the bone tissue - there it is associated with a specific protein called osteocalcin. And the formation of this complex is largely mediated by a preliminary carboxylation reaction of this protein, carried out by a menaquinone-dependent enzyme. A decrease in the concentration of this vitamin leads to a decrease in the affinity of osteocalcin for calcium - and, therefore, disrupts its deposition in the bones, which leads to the development of osteoporosis.

In addition, K2 also regulates the effects of the MGP protein synthesized by cartilage tissue cells and smooth myocytes, which prevents the deposition of this mineral on the inner lining of blood vessels, thereby preventing the occurrence of atherosclerotic disease, in the pathogenesis of which, in addition to cholesterol, leakage of the vessel wall also plays an important role. calcium.

Functions of Vitamin A

Many still remember from biology lessons about the need for the body to receive the proper amount of vitamin A for the normal functioning of the visual pigment of the retina - rhodopsin. However, often limiting ourselves to theory alone, we do not always think about the scale of the problem. Why is the issue of retinol hypovitaminosis no less acute than calciferol deficiency?

Foreign researchers cite impressive statistics: insufficient intake of vitamin A with food is the annual cause of vision loss in more than - just think about these numbers! — 500,000 school-age children.

The process of converting vitamin A from its precursors into its active forms largely depends on the functioning of the BCMO1 gene and the presence of polymorphisms in it - and if they are, even eating a kilogram of carrots, you will not be able to replenish the reserves of retinol that your body needs.

In addition, a breakdown in the gene responsible for the synthesis of the retinol-binding protein, RBP4, can also contribute to a decrease in the concentration of this compound in our body. It is interesting that this protein acts, according to the latest data, as a marker of metabolic syndrome - another disease of civilization. There are quite reliable prerequisites for this: for example, in the studied groups of patients, an increase in RBP4 was accompanied by an increase in the level of triglycerides in the blood serum, a decrease in the concentration of “good”, i.e. anti-atherogenic high density lipoproteins, an increase in blood pressure and body mass index.

Interesting from the point of view of science and new ground for research is the relationship of retinol with thyroid hormones, indirectly realized through their common protein carrier - TTR or Trans-Ti-Retin. Its colossal importance for the normal functioning of the nervous system is explained, first of all, by its main function: the delivery of thyroid hormone T4 to the neurons of the brain, where thyroxine is further converted into the more metabolically active T3 - triiodothyronine. When these processes are disturbed, a whole complex of neurodegenerative disorders is observed, including dementia.

However, no less important is the transport of TTR to the conductor of the whole organism - the central nervous system - and retinol - the form of vitamin A you already know. The fact is that retinoids affect the expression of numerous genes responsible for both the formation of receptors for mediators and the neurotransmitters themselves , signaling molecules and specific enzymes that regulate their metabolism. Moreover, they are also involved in the regulation of growth and further differentiation of nerve cells - all this creates a very clear understanding that vitamin A deficiency is not limited to only a decrease in twilight vision - cognitive disorders, manic syndrome, depression and even schizophrenia are observed.

A decrease in the content of vitamin A and its various forms (retinol, dehydroretinol, retinal, retinoic acid) is usually manifested by the following most common set of symptoms:

1. Dryness of the cornea is a consequence of blockage of the lacrimal canal, which is observed due to keratinization of the epithelium lining it from the inside. This is normally prevented by retinol, which also stimulates the formation of the constituent components of mucus.

   In the future, this violation can lead to much more serious consequences: the development of purulent processes due to the lack of antibacterial secretions of the lacrimal glands (in particular, those containing secretory immunoglobulin A, a representative of one of the class of antibodies).

2. Hyperkeratosis - especially noticeable in places where the joints are bent: in the area of ​​​​the elbows. It is also clearly expressed in the area of ​​the forearms.

3. Increased risk of developing malignancies—for example, colorectal cancer.

4. Brittle nails and dull hair.

5. Tendency to infectious diseases, usually turning into a sluggish form and / or chronic.

6. Keratinization (keratinization) of the glandular epithelium, as a result, disruption of the functioning of organs of various systems: in particular, the gastrointestinal and genitourinary tracts.

7. “Night blindness” is a violation of night vision. This happens due to an increase in the visual threshold - in other words, there is a change in the intensity of light that causes a visual sensation.

Intake of fat-soluble vitamins

Features of the use of vitamins A, D, E, K

It is necessary to consume these vitamins together with the main, fat-rich food, not combined with the intake of water-soluble vitamins (or after making sure that there are no pronounced antagonistic relationships).

For the processes of digestion, and then splitting, given the chemical nature of this class of organic compounds, a normal outflow of bile is required, which acts as an emulsifier and, in addition, an activator of pancreatic enzymes.

Therefore, before starting a new course of using dietary supplements, make sure that the liver properly performs its synthetic function, and the gallbladder adequately evacuates a portion of golden brown bile at the moment of irritation of the receptors localized in the digestive tract. If there are certain violations at this stage of digestion, you will simply waste your money, time and effort: there can be no question of any process of absorption. Contact a nutritionist - a competent nutritionist and / or gastroenterologist will draw up the correct work scheme for you.

It is important to first understand the cause of such pathologies: for example, drinking choleretic drugs when the bile duct is blocked by a calculus is extremely unreasonable and even dangerous. Start with diagnostics - ultrasound of the abdominal organs should be among the mandatory items in the annual check-up of examinations.

To establish bile outflow (in the absence of mechanical obstruction of the biliary tract), you can consider taking stimulants of this process:

• Wormwood tinctures.

• Dandelion root.

• Swedish bitters.

In addition, the development of cholestasis is also prevented by non-toxic ursodeoxycholic acid, which, in addition, has anti-inflammatory and litholytic effects.

The dangers of fat-soluble vitamins

Do not forget that all fat-soluble vitamins must be strictly drunk in courses and only after preliminary laboratory tests - and all because of their characteristic ability to accumulate (in particular, in the liver). And the symptoms of hypervitaminosis, unfortunately, are often similar to those that accompany the lack of these vital compounds.

So, let's say, an excess of vitamin A leads to a number of effects that threaten not only an individual organ, but also life in general:

• nausea and vomiting;

• papilledema;

• dizziness and migraine;

• an increase in the size of the liver - hepatomegaly;

• increased intracranial pressure;

• hemorrhage and bleeding.

We also want to emphasize that, despite all the numerous beneficial effects of calcitriol, and the real excitement that reigns around it, one should not forget about one of its leading effects: the regulation of mineral metabolism. Vitamin D, through the formation of a specific carrier, stimulates the absorption of calcium from the intestines, an element whose deficiency associated with insufficient nutritional coverage of the body's needs is extremely rare.

The place of calcium is in the bone and dental tissue, where it is deposited in a bound form. Undoubtedly, this is a key element involved in the transmission of nerve impulses (in particular, in neuromuscular junctions-synapses), blood coagulation and hormone secretion. But at the same time, its excess in the blood serum is accompanied by significant disturbances in the work of internal organs. Are noted:

• increased cardiac output and the development of tachycardia, hypertension, and arrhythmias;

• muscle weakness;

• impaired renal function;

• headache and depression.

We do not recommend, in the absence of indications and without laboratory tests confirming hypocalcemia, to take a complex of dietary supplements containing calcium together with vitamin D.

Foods rich in fat-soluble vitamins

Vegetable products contain precursors of retinol - carotenoids. One of them, beta-carotene, has pronounced antioxidant properties and, due to this, protects cells, including the nervous system, from free radicals, which allows it to be used in the treatment of oncological diseases. In the liver, by oxidative cleavage, it is transformed into vitamin A.

The following foods are rich in carotenoids:

1. Yellow and orange vegetables:

   • pumpkin;

   • pepper;

   • carrot.

2. Green vegetables, in particular:

   • broccoli;

   • spinach;

   • sorrel;

   • parsley and other herbs.

3. Various fruits and bright, juicy berries:

   • apricots;

   • rose hip;

   • peaches;

   • grape;

   • sweet cherry;

   • melon;

   • sea ​​​​buckthorn.

4. Legumes and grains: oats, peas, soybeans.