Water-soluble Vitamins: Daily Requirement And Rules For Use

Vitamins or “vital amines”, as they were called at the time of discovery, are low molecular weight compounds that, with rare exceptions, as a rule, are not formed by the microflora of our body and come purely with food components or as part of biologically active additives.

Perhaps their main and most important function is their participation as coenzymes - the necessary structural units of all enzymes that ensure the occurrence of certain groups or purely specific biochemical reactions.

The difference between water and fat soluble vitamins

However, in fairness, it should be said that the basis of each enzyme is no less important - its protein part or apoenzyme: it is the protein nature that puts the parameters of homeostasis into such a strict, clearly regulated framework, within which the functioning of each enzyme is carried out. The slightest shift of this balance towards acidification (acidosis) or vice versa - alkalinization (alkalosis) of the environment, as well as an increase in temperature lead to a total collapse in the factory in terms of their functioning.

All vitamins, based on their chemical structure, lipo- and hydrophilicity, can be divided into two large groups: water- and fat-soluble.

Let's delve a little more into the biology of our body and rise a little higher: from the molecular level to the cellular level - it is he who will allow us to better understand the differences, and, therefore, the difference in the pharmacodynamic effect provided by such different categories of "vital amines".

Each cell is separated by a plasma membrane - a truly amazing structure that not only strictly delimits the extra- and intracellular environment, but also selectively passes some substances, being absolutely impregnable for others. At the heart of its framework is the bilipid layer of lipids - everyone remembers, for sure, from school about two rows of phospholipids facing each other with tails. They are integrated, like Lego bricks, proteins (although a certain proportion does not penetrate our most important barrier completely, being located purely on its surface) and cholesterol molecules that give lability.

There are several mechanisms of transport - the process that, in our case, ensures that certain molecules get inside, that is, into the cytoplasm. Let us dwell on the most important thing for understanding today's article - diffusion. It is carried out without any energy consumption - and this is the first point that you should pay attention to: after all, there are many reactions and functions that require the consumption of ATP. It happens due to the concentration gradient - in other words, the substance moves to where its level is much lower.

However, at the beginning we did not talk in vain about the selectivity of membranes: this is a kind of passport control, for passing which it is necessary to have certain properties. And, perhaps, the main thing is fat solubility, which helps, literally, to squeeze between phospholipid molecules.

Now, having finally completed a short digression into the physiology and biochemistry of some of the most interesting topics in the context of this article, we can draw one more conclusion that fundamentally distinguishes the previously classified groups of vitamins. Fat-soluble vitamins (this is especially true, as has been proven by the results of recent studies, A and D) are capable of penetrating into the very inside, the core of the cell and affecting its nuclear apparatus, to regulate the expression of several thousand genes - this gives a solid reason to talk not only about the coenzyme function vitamins.

List of water soluble vitamins

Functions of Vitamin C

Ascorbic acid is necessary for the formation and maintenance of the normal structure of collagen - it acts as a coenzyme in the hydroxylation reactions of proline and lysine - the most important amino acids in this main connective tissue protein.

It also hydroxylates other, no less significant (both for the proper functioning of our body, and, as we will soon see, for the correct diagnosis of its hypovitaminosis) amino acids:

• tyrosine is a precursor of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine), adrenaline, melanin pigment, as well as a number of neurotransmitters: dopamine and norepinephrine;

• tryptophan is a raw material for the synthesis of serotonin and melatonin, as well as niacin - vitamin B3.

In addition, ascorbic acid is involved in the reduction of ferric iron to ferrous iron - this is observed in the intestine and contributes to a better absorption of this element; and also in the blood, which ensures its release from its association with the transferrin carrier protein.

Functions of B vitamins

The vitamins of this group include: B1, B2, B3, B5, B6, B9 and B12. Let's look at the most important effects some of them have.

1. Vitamin B1 - directly affects the course of biochemical reactions that ultimately provide the body with energy. This effect is achieved due to its two coenzyme forms, which catalyze both the reactions of the Krebs cycle - that, in fact, the main furnace of our cells, and the conversion of keto acids in such a glucose utilization mechanism as the pentose phosphate pathway. The latter, by the way, gives our body the two most important substrates: structural building blocks for building nucleic acids (DNA and RNA), as well as NADPH2, which is a derivative of vitamin B3 and is the most important factor preventing hemolysis (destruction of red blood cells) - probably, in part this contributes to the remarkable fact that up to 80% of the total pool of B1 coenzyme forms is located in red blood cells.

   However, the effects of thiamine are not limited to the catalytic function alone - for example, in the nervous system it ensures the maintenance of a certain concentration of sodium and potassium ions, the ratio of which plays a key role in the development of excitation and inhibition of neurons, as well as the conduction through specific contacts - synapses - of an impulse from one nerve cell to another or to an effector organ (skeletal muscle and/or gland).

    

   Vitamin B1 does not accumulate in the body: this is due to the fact that, being in a free form - that is, without forming complexes with proteins, the bulky molecules of which normally simply do not pass through the thin, narrow cells of the renal filter - are easily excreted along with urine .

   Thiamine is not formed in our body - we can get it purely from the outside: that is, with food and biological supplements.

    

2. Vitamin B2 or riboflavin is also involved in key reactions of energy production. In addition, it is necessary in a number of other processes that are so often forgotten:

   • fatty acid oxidation;

   • restoration of glutathione - and, therefore, for detoxification;

   • the inclusion of iron and copper in the precursor cells of erythrocytes - thus, it is involved in hematopoiesis (more precisely, in erythropoiesis);

   • participates in the formation of parietal cells of the gastric mucosa of hydrochloric acid;

   • is part of visual purple and, along with retinol, provides adaptation in the dark.

    

3. Vitamin B3, PP or niacin - its coenzyme forms are involved in such a mechanism for the utilization of simple sugars as glycolysis, as well as in oxidative phosphorylation - in essence, the final stage on the energy production conveyor belt. In addition, they also take part in the formation of bile acids and steroid hormones produced by both the gonads and the adrenal cortex - this function is ensured by their direct participation (together with vitamin C) in the biotransformation of cholesterol.

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   A small part of the needs of the human body can be covered by the endogenous formation of this vitamin - however, this process requires the proper supply of the substrate, which is the amino acid tryptophan, and catalyzes one of the stages of vitamin B6. Therefore, based on the described mechanism of niacin synthesis, at least 3 reasons for its possible deficiency can be identified:

   • violation of protein breakdown - for example, with hypochlorhydria - a decrease in the secretion of hydrochloric acid by the parietal cells of the stomach;

   • absorption deterioration is a consequence of malabsorption syndrome or, say, a much more serious pathology - genetically determined Hartnup's disease;

   • vitamin B6 deficiency, which, in turn, is observed with a decrease in the concentration of riboflavin, which is necessary for the formation of its active form - pyridoxal-5-phosphate.

    

4. Vitamin B6 is a coenzyme in decarboxylation reactions that provide the formation of:

   • various neurotransmitters: dopamine, norepinephrine, adrenaline;

   • thyroid hormones - triiodothyronine and thyroxine;

   • heme - one of the key structures in the hemoglobin molecule, the most important task of which is the transfer of carbon dioxide and oxygen from tissues to the alveoli and vice versa;

   • vitamin B3 or niacin;

   • melatonin and serotonin.

1. Vitamins B9 and B12 - perhaps one of their most important functions - participation in the folate cycle, which, by sequential transfer of the methyl group CH3-, leads to the formation of both vital elements (for example, choline), and to DNA methylation, regulation of metabolism such an inflammatory mediator as histamine, and the synthesis of creatinine.

Deficiency of water-soluble vitamins

1. Insufficient intake of thiamine (B1) along with food, its excessive excretion or consumption, in general, is characterized by the following clinical manifestations:

   a) The development of the dry form of beriberi, in which the leading symptoms are due to disorders in the central and peripheral nervous systems. In particular, the following are noted:

   • decreased sensitivity;

   • burning in the limbs - especially the feet;

   • convulsions;

   • muscle weakness.

   b) The wet form of beriberi is a consequence of a decrease in energy reserves (and we said that the coenzyme forms of thiamine are involved in key reactions in the mitochondrial ovens of the human body) in the cells of the contractile myocardium, which also affects the cardiac output itself. B1 deficiency contributes to:

   • violation of acid-base balance (strictly regulated for the work of each of the enzymes) - the pH of the medium shifts to a more acidic side;

   • water and sodium retention - edema develops;

   • difficulty breathing.

   c) Cerebral beriberi or Wernicke-Korsakoff syndrome is a disease that, as previously thought, only affects patients suffering from chronic alcoholism. The most characteristic triad of symptoms for this pathology includes:

   • eye movement abnormalities;

   • confusion and amnesia;

   • violation of walking and posture.

   In general, moderate thiamine hypovitaminosis is usually accompanied by less severe, but clinically significant signs:

   • polyneuritis;

   • anxiety, cognitive impairment;

   • fatigue and lack of strength are a direct consequence of a decrease in energy production;

   • numbness of hands and feet;

   • deterioration in coordination.

1. B2 deficiency is accompanied by a characteristic, striking set of symptoms:

   • seizures in the corners of the mouth - the main and fairly common complaint;

   • cracks on the outer surface of the lips, as well as their soreness;

   • vascularization of the cornea - the formation of blood vessels in it, which further leads to clouding of this shell of the eyeball;

   • seborrheic dermatitis - peeling of the skin;

   • hair loss - alopecia;

   • pain in the eyes - we have already mentioned that riboflavin is part of the visual pigment rhodopsin;

   • fatigue and lack of strength, decreased performance.

    

2. B3 deficiency - underlies the occurrence of such a disease as pellagra, which is accompanied by a complex of three "D":

   • dermatitis;

   • diarrhea;

   • dementia;

   • in English-language literature, a fourth is added - death (death).

   In addition, apathy, depression and fatigue are characteristic - the result of a decrease in the amount of energy formed in the body.

    

3. B6 deficiency is accompanied by ulcers in the oral cavity, seborrheic and atopic dermatitis (a consequence of impaired formation of vitamin B3 from tryptophan), hyperhomocysteinemia.

1. Deficiency of B9 and B12 - in general, leads to disruption of the folate cycle and, as a result, an increase in the blood level of such an amino acid as homocysteine, which is widely known for its damaging effect on the endothelium - the inner lining of blood vessels - and is a leading marker of cardiovascular pathologies .

2. The lack of ascorbic acid - first of all, affects the structure of such a connective tissue protein as collagen. A decrease in the course of reactions of hydroxylation of amino acids in its composition ultimately leads to an incorrect structure of the protein - one of the components of the vascular wall. Are noted:

• bleeding from the gums and nasal cavity;

• deterioration and slowdown in wound healing (after all, the scar formed at the site of injury is also based on connective tissue);

• petechiae - pinpoint hemorrhages.

Inhibition of hydroxylation reactions also affects the fluidity of bile - a decrease in the content of bile acids in it becomes a significant risk factor for stone formation in the ducts.

Diagnosis of deficiency of water-soluble vitamins

1. Vitamin B1.

   Determination of the concentration of thiamine in the blood serum has no diagnostic value. In general, the clinical picture of his hypovitaminosis is quite characteristic, but if laboratory tests are still needed to accurately establish the diagnosis, be guided by an increase in the following indicators in analyzes for organic acids in the urine:

   • pyruvic acid;

   • lactic acid;

   • alpha-ketoglutaric acids;

   • 2-ketoisovaleric, 2-methyl-2-oxovaleric, 4-methyl-hydroxyvaleric acids.

    

2. Vitamin B2 - increasing the values ​​of such organic acids:

   Adipinova

   Suberic

   Succinic

    

3. Vitamin B3 - as a rule, an increase in concentration is observed:

   isocitrate

   Alpha-ketoglutaric acid

   Fumarate

    

4. Vitamin B6:

   • direct markers: xanthurenic and kynurenic acids in urine;

   • indirect - an increase in the concentration of homocysteine.

    

5. Vitamin B9 - increase:

   Forminoglutamic acid (early marker)

   Methylhistidine

   Glycine

    

6. Vitamin B12:

   Increase in methylmalonic acid

   Increase in KLA MCV, MCH

   (typical for folic acid deficiency)

   Increasing the concentration of homocysteine

   (sign of deficiency B6, B9, B12)

    

7. Vitamin C deficiency:

   Organic acids in urine:

   increase in hydroxyphenyl lactic acid;

   an increase in homogentisic acid;

   Amino acids in urine:

   hydroxyproline;

Foods rich in water-soluble vitamins

Rules for the use of additives

First of all, you need to make sure that you are not taking an inhibitor of this or that vitamin with it - that is, a substance that would disrupt its absorption, distribution, or biotransformation in liver cells. Below we have listed some of the most pronounced antagonists.

1. Cyanocobalamin antagonists:

   • proton pump inhibitors - reduce the secretion of hydrochloric acid (for example, omeprazole);

   • antagonists of histamine (H2-) receptors - also lead to hypochlorhydria;

   • colchicine - a drug for the treatment of gout;

   • some antibiotics: chloramphenicol.

    

2. The absorption of vitamin B9 is suppressed by:

   • long-term use of non-steroidal anti-inflammatory drugs;

   • drugs used to lower cholesterol levels (cholestyramine);

   • some antibiotics and chemotherapy drugs

3. Excretion from the body of thiamine is increased by:

   • alcohol;

   • tea;

   • coffee.

Daily requirement for water-soluble vitamins

(according to K. Astill-Smith and K. Reardon)