Textbook - BIOLOGICAL CHEMISTRY - Gubsky Yu.I. - 2000

Chapter VI. BIOCHEMISTRY OF PHYSIOLOGICAL FUNCTIONS AND SPECIALIZED TISSUES

CHAPTER 27. HUMAN NUTRITION BIOCHEMISTRY. II. VITAMINS AS DIETARY COMPONENTS

27.1. VITAMINS AS COMPONENTS OF HUMAN NUTRITION; DISEASES OF VITAMIN DEFICIENCY

Vitamins are bioorganic compounds that are essential components of METABOLISM; unlike other Biomolecules, vitamins are not synthesized in The Human Body and must be obtained from dietary sources. In contrast to Macronutrients such as CARBOHYDRATES, Lipids, and Proteins, vitamins are classified as dietary micronutrients, with human daily requirements amounting to milligram or microgram quantities.

The discovery of vitamins is associated with the work of numerous researchers—physicians, biochemists, and physiologists—who established the presence in foods of specific compounds necessary for normal vital activity, termed "accessory food factors." Specific nutritional deficiency diseases such as scurvy, beriberi, pellagra, Rickets ("the English disease"), and hemeralopia ("night blindness") have been known to humanity for centuries. The first vitamin proven to be an essential dietary factor was thiamine (vitamin B₁), isolated in 1911 by the Polish researcher C. Funk from rice bran. The compound isolated by Funk prevented The Development of beriberi (polyneuritis caused by prolonged consumption of polished rice) and contained an amino group in its Structure, which formed the basis for the term "vitamins" (from Latin vita, life, and amin) proposed for all accessory food factors.

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Fig. 27.1. Kazimierz Funk (1884–1967), Polish biochemist who worked in various European countries and the USA. One of the founders of vitamin science.

Classification of Vitamins

Considering that the Discovery of the first vitamin preparations significantly preceded the elucidation of their chemical structure, empirical names (nomenclature) historically developed, utilizing a capital letter of the Latin alphabet with a numerical index; modern vitamin names also indicate their chemical nature and, in some cases, their primary biological effect with the prefix "anti-".

Depending on their physicochemical properties (solubility in Water or lipids), vitamins are divided into two major groups: water-soluble and fat-soluble.

Water-Soluble Vitamins

Vitamin B (thiamine; antineuritic vitamin).

Vitamin B₂ (riboflavin).

Vitamin PP (vitamin B₅; niacin; antipellagra vitamin).

Vitamin B₆ (pyridoxine; antidermatitic vitamin).

Vitamin B₁₂ (cobalamin; antianemic vitamin).

Folic acid (pteroylglutamate; antianemic vitamin).

Vitamin H (biotin; antiseborrheic vitamin).

Pantothenic acid (vitamin B₃; antidermatitic vitamin).

Vitamin C (ascorbic acid).

Vitamin P (permeability vitamin).

Fat-soluble vitamins

Vitamin A (retinol; axerophthol; growth vitamin).

Vitamin K (phylloquinone; antihemorrhagic vitamin).

Vitamin E (α-tocopherol; reproduction vitamin).

Vitamin F (a complex of polyunsaturated Fatty acids).

Vitamin D (calciferol; anti-rachitic vitamin).

Vitamin deficiency is a condition that develops As a result of a decrease (or complete lack) of a specific vitamin in the body. Vitamin deficiency is accompanied by severe disruptions in biochemical and physiological processes and the onset of specific pathology.

A distinction is made between hypovitaminosis and avitaminosis, which are pathological states characterized by relative or complete vitamin deficiency in the Tissues, respectively. The primary causes of vitamin deficiency states (hypo- and avitaminoses) include:

1. Reduced intake (or absence) of a specific vitamin in the body through food (resulting from poor dietary choices or improper food preparation); such conditions are termed exogenous hypo-(a-)vitaminoses.

2. Impaired assimilation of certain vitamins by body Cells (due to malabsorption in the digestive tract or the inability of biochemical systems to incorporate the vitamin into metabolic processes, particularly due to the presence of structural competitors—Antivitamins)—resulting in endogenous hypo-(a-)vitaminoses.

3. Increased excretion of vitamins from the body or their accelerated utilization in biochemical and physiological processes (situations that may occur during Lactation, Pregnancy, exhausting physical labor, exposure to extreme Temperature conditions, or severe infectious diseases, etc.).

Under conditions of hypo- and avitaminosis, profound disruptions occur in specific metabolic processes and cellular Functions in which vitamins participate as specific biomolecules. By their MECHANISM OF ACTION, vitamins serve as Coenzymes for complex Enzymes (or participate in the synthesis of coenzymes as constituent components), are incorporated into Biomembranes, and perform specific regulatory functions at the level of individual Cellular Structures and the Organism as a whole.