A general group of fat-like substances insoluble in water. Fats and fat-like substances (lipids). The role of fats in nutrition is determined by their high calorie content and participation, together with proteins, in plastic processes. Fat that is part of cellular structures, h
They are of significant value to the body fat-like substances (lipoids). These include biologically active substances - phospholipids And sterols.
Phospholipids (phosphatides)– the main representatives are lecithin, cephalin and sphingomyelin. In the human body, they are part of cell membranes and are essential for their permeability, metabolism between cells and the intracellular space.
Phospholipids in food products differ in their chemical composition and biological effects. The latter largely depends on the nature of their constituents. amino alcohol.
Most widely represented in food products lecithin. Lecithin contains glycerin, unsaturated fatty acids, phosphorus and vitamin-like substance choline. Lecithin has lipotropic action - reduces the accumulation of fats in the liver, promoting their transport into the blood. It is part of the nervous and brain tissue and affects the activity of the nervous system. Lecithin is an important factor in regulating cholesterol metabolism, because prevents the accumulation of excess amounts of cholesterol in the body, promotes its breakdown and elimination. A sufficient amount of lecithin is of great importance in diets for atherosclerosis, liver diseases, cholelithiasis, in the diets of mental workers and the elderly, as well as in diets for therapeutic and therapeutic-and-prophylactic nutrition.
The daily need for lecithin is about 5 g. Eggs (3.4 g%), liver, caviar, rabbit meat, fatty herring, unrefined vegetable oils (2.5-3.5 g%) are rich in lecithin. Beef, lamb, pork, chicken meat, peas contain about 0.8 g% lecithin, most fish, cheese, butter, oatmeal - 0.4-0.5 g%, full-fat cottage cheese, sour cream - 0. 2 g%. A good low-fat source of lecithin is buttermilk.
Sterols are hydroaromatic alcohols of complex structure contained in vegetable oils (phytosterols) and animal fats (zoosterols).
The best known of the phytosterols is ß-sitosterol, most of it is found in vegetable oils. It normalizes cholesterol metabolism, forming insoluble complexes with cholesterol that prevent the absorption of cholesterol in the gastrointestinal tract, and thereby reduce its content in the blood.
Cholesterol refers to animal sterols. It is a normal structural component of all cells and tissues. Cholesterol is part of cell membranes and, together with phospholipids and proteins, ensures selective permeability of membranes and affects the activity of enzymes associated with them. Cholesterol is the source of the formation of bile acids, steroid hormones of the gonads and adrenal cortex (testosterone, cortisone, estradiol, etc.), vitamin D.
It should be highlighted relationship between dietary cholesterol and atherosclerosis, the causes of which are complex and diverse. It is known that cholesterol is part of complex plasma proteins lipoproteins. There are high-density lipoproteins (HDL), low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL). TO atherogenic, those. promoting the formation of atherosclerosis include LDL and VLDL. They are capable of depositing on the vascular wall and forming atherosclerotic plaques, as a result of which the lumen of the blood vessels narrows, the blood supply to the tissues is disrupted, and the vascular wall becomes weak and fragile.
The bulk of cholesterol in the body is formed in the liver (about 70%) from fatty acids, mainly saturated. A person receives part of cholesterol (about 30%) from food.
The qualitative and quantitative composition of food significantly affects cholesterol metabolism. The more cholesterol comes from food, the less it is synthesized in the liver and vice versa. When saturated fatty acids and easily digestible carbohydrates predominate, cholesterol biosynthesis in the liver increases, and when PUFAs predominate, it decreases. Cholesterol metabolism is normalized by lecithin, methionine, vitamins C, B6, B12, etc., as well as microelements. In many products, these substances are well balanced with cholesterol: cottage cheese, eggs, sea fish, some seafood. Therefore, individual products and the entire diet must be assessed not only by cholesterol content, but also by a combination of many indicators. Currently, saturated fatty acids from animals and hydrogenated fats are considered more significant risk factors for the development of cardiovascular pathology than dietary cholesterol.
Cholesterol is widely present in all foods of animal origin (Table 3).
A typical daily diet should contain no more than 300 mg of cholesterol. When cooked, about 20% of cholesterol is destroyed.
Table 3.
5.6. Sources of fats in the diet
None of the dietary fats, taken separately, can fully meet the body's needs for them. So , animal fats, including milk fat, have high taste, contain quite a lot of vitamins A and D, lecithin, which has lipotropic properties. However, they are low in PUFAs and high in cholesterol, one of the risk factors for atherosclerosis.
Vegetable fats contain a lot of PUFAs, vitamin E and ß-sitosterol, which help normalize cholesterol metabolism. At the same time, vegetable oils lack vitamins A and D, and when cooked, these oils easily oxidize.
Sources of animal fats are pork fat (90-92% fat), butter (62-82%), fatty pork (49%), sausages (20-40%), sour cream (10-30%), cheeses (15-30%). 45%), etc.
Sources of vegetable fats - vegetable oils (99.9% fat), nuts (53-65%), oatmeal (6.1%), buckwheat, millet (3.3%), etc.
A healthy diet should include a combination of animal and vegetable fats.
Fats and fat-like substances (lipids) are derivatives of higher fatty acids, alcohols or aldehydes. They are divided into simple and complex. Simple lipids include lipids whose molecules contain only residues of fatty acids (or aldehydes) and alcohols. Among the simple lipids found in plants and animal tissues are fats and fatty oils, which are triacylglycerols (triglycerides) and waxes. The latter consist of esters of higher fatty acids and mono- or diatomic higher alcohols. Close to fats are trostaglandins, which are formed in the body from polyunsaturated fatty acids. By chemical nature, they are derivatives of prostanoic acid with a skeleton of 20 carbon atoms and containing a cyclopentane ring.
Complex lipids are divided into two large groups: phospholipids and glycolipids (i.e. compounds containing a phosphoric acid residue or a carbohydrate component in their structure).
Fatty oils of plants and fats of reserve tissues of animals, along with carbohydrates, represent a concentrated energy and construction reserve of the body. Up to 90% of plant species contain storage fats in their seeds. In addition to seeds, reserve fats can accumulate in other plant organs. Plants characterized by a high oil content in seeds and fruits in the tropics and subtropics are represented mainly by trees (palm trees, tung, castor beans, etc.). In areas with a temperate climate, these are mainly herbaceous plants (flax, sunflower, etc.), less often shrubs, and even less often trees. The accumulation of fats in plants can be quite significant; for example, in domestic sunflower varieties, the oil content sometimes reaches 60% of the kernel weight.
Spare fats also serve as protective substances that help the body endure unfavorable environmental conditions, in particular low temperatures. Accumulating in the endosperm or in the cotyledons of “overwintering” seeds, fats allow the embryo to be preserved in frost conditions. In trees in temperate climates, when entering a dormant state, the reserve starch of the wood turns into fat, which increases the frost resistance of the trunk. In animals, fats are final or temporary reserve substances. Finite reserves, such as milk fat, are not used by the body. Only temporary storage fats, typical of adipose tissue, are mobilizing products. It is these fats that simultaneously serve humans as products for food, medicinal and technical purposes.
Structure of fats
Fats consist almost exclusively of mixtures of fatty acid glycerides, which are esters of glycerol and high molecular weight fatty acids, most often triglycerides. Triglycerides have the general formula:
More than 200 different fatty acids are found in natural fats. The predominant ones are fatty acids with an even number of carbon atoms from C 8 to C 24. Fatty acids with a short chain of less than 8 carbon atoms (capronic, butyric, etc.) are not found in triglycerides, but they can be present in free form, affecting the smell and taste of fats. Most fats contain 4-7 main and several accompanying (constituting less than 5% of the total) fatty acids. Suffice it to say that up to 75% of global fat production is made up of triglycerides of three acids - palmitic, oleic and linoleic.
The fatty acids contained in triglycerides can be saturated or unsaturated. In table 1 shows the list and structure of fatty acids most often included in triglycerides. The fats of some plants contain specific fatty acids that are characteristic only of these plants. So, for example, castor bean oil contains hydroxy acid - ricinoleic acid, chaulmugro fatty oil is formed by glycerides of cyclic acids - hydrocarpic, chaulmugra, etc.
Triglycerides can be single-acid or mixed-acid (mixed). In mono-acid triglycerides, esterification of glycerol occurred with three molecules of the same fatty acid (for example, triolein, tristearin, etc.). However, fats consisting of monoacid triglycerides are relatively rare in nature (olive oil, castor oil). The formation of fats is dominated by the law of maximum heterogeneity: the vast majority of known fats are mixtures of different acid triglycerides (for example, stearin diolein, palmitino diolein, etc.). Currently, over 1,300 fats are known, differing in the composition of fatty acids in the multi-acid triglycerides they form.
Fat-like substances include:
Phospholipids
Sphingolipids
Glycolipids
Steroids
Cutin and suberin
Fat-soluble pigments
(chlorophylls, carotenoids, phycobilins).
Glycolipids - these are fat-like substances in the molecules of which glycerol is connected by an ester bond with two fatty acid residues and a glycosidic bond with some sugar. Glycolipids are the main lipids of chloroplast membranes. There are approximately 5 times more of them in photosynthetic membranes than phospholipids.
Steroids. The steroids are based on 4 fused carbocycles: 3 six-membered and 1 five-membered. In animal organisms, cholesterol and a number of hormones have a steroid nature. In plants, steroids are more diverse. More often they are represented by alcohols - sterols. About 1% of sterols are linked by ester bonds to fatty acids - palmitic, oleic, linoleic and linolenic.
Ergosterol is common in plants, as well as yeast, ergot horns, and mushrooms. Vitamin A is formed from it under the influence of ultraviolet radiation.
ergosterol 
-sitosterol
Sterols are part of plant cell membranes and are believed to be involved in the control of permeability. It was found that the bulk of plant cell sterols are contained in the membranes of the ER and mitochondria, and their esters are associated with the cell wall fraction.
Wax. Waxes are contained in the cuticle and form a thin layer on its surface. A waxy coating covers the leaves, stems and fruits, protecting them from drying out and being damaged by microorganisms.
Wax - These are fat-like substances that are solid at room temperature. The composition of waxes includes esters of fatty acids and monohydric high-molecular fatty alcohols. In addition, waxes contain free fatty acids and alcohols, as well as paraffin hydrocarbons.
The composition of waxes varies from plant to plant. For example, the wax of cabbage leaves consists mainly of C 29 -hydrocarbon and its derivatives containing the carbonyl group =C=O. Grape berry wax contains esters of palmitic acid, ceryl and myricyl alcohols.
Plant waxes are used in the manufacture of candles, lipsticks, soaps, patches, and shampoos. For example, a significant amount of wax is secreted on the surface of the leaves of the Palma ceprpega palm, which grows in South America - up to 5 mm. This wax is called carnauba wax. It is hard and brittle, yellowish-greenish in color, and is used to make candles.
A unique wax is found in the fruits and seeds of Simonzia Californian, or jojoba, native to the southwestern United States and northwestern Mexico. This wax is liquid. For a long time it was mistaken for oil. For a long time, the Indians have been eating it and using its medicinal properties (wound healing, etc.) - And only relatively recently did they find out that it does not contain triglycerides, but esters of high-molecular acids and monohydric alcohols. In addition, this wax is the only one so far that is a reserve nutrient and is used during seed germination.
Cutin and suberin - these are fat-like substances that cover or permeate the walls of the integumentary tissues (epidermis, cork), increasing their protective properties. Kutin covers the epidermis with a thin layer on top - cuticle, which protects underlying tissues from drying out and penetration of microorganisms. Cutin contains C16 and C18 fatty hydroxy acids - saturated and monounsaturated. Hydroxyl groups - from one to three - are located at the end, as well as in the middle, of the acid's carbon chain. These groups bond with carboxyl ester bonds, resulting in a complex three-dimensional cutin structure that is highly resistant to various influences.
Suberin - a polymer that impregnates the cell walls of the cork and primary root cortex after desquamation of root hairs. This makes the cell walls strong and impermeable to water and gases, which, in turn, increases the protective properties of the integumentary tissue. Suberin is similar to cutin, but there are some differences in the composition of the monomers. In addition to the hydroxy acids characteristic of cutin, suberin contains dicarboxylic fatty acids and dihydric alcohols. The bonds between monomers are the same - ester bonds, which are formed by the interaction of hydroxyl and carboxyl groups.
From crude oil extracted from the depths of the earth, various petroleum and waxy products are obtained by distillation. In cosmetics, primarily liquid flowing paraffin (or white) oil, viscous dense petroleum jelly, hard, waxy mountain wax (or ozokerite) and purer paraffin are used.
Paraffin oil is a transparent, odorless, tasteless oily substance that can be of varying densities.
Vaseline is a white, viscous, sticky, oily substance that is odorless. In this form, it is used as an ointment for massage, and also as a base for the preparation of various medicinal ointments.
Ozokerite and paraffin are solid white substances of variable density.
All these petroleum-derived raw materials are widely used in the cosmetics industry due to their low price and good storage stability. They cannot be easily absorbed into the skin, but are an excellent source material for the production of, for example, gel and cosmetic milk, as well as for decorative cosmetics.
Natural oils, due to the presence of unsaturated bonds in them, are less viscous and more fluid than fats. Both oils and fats are esters of fatty acids and glycerol; in nature they are always found in the form of various mixtures. Natural fats quickly deteriorate due to their chemical unsaturation. Therefore, they are often hydrogenated by adding hydrogen atoms at unsaturated bonds. In this form, the fat becomes hard and is better preserved, but at the same time it becomes less suitable for use in cosmetics3.
Fats of plant and animal origin are still used for the production of cosmetic substances, although for the above reasons they are increasingly giving way to synthetic substances, fatty acids, fatty alcohols, etc. The most important plant and animal oils and fats are the following (Table 1)4.
Table 1 Vegetable and animal oils and fats
In addition to the above, some other natural oils are also used, since they contain certain additional substances. The following are examples.
Turtle oil in its raw form is yellow in color and has a very unpleasant odor (it is obtained by extracting it from the genitals and muscles of a species of turtle). It contains, in particular, vitamins A, O, K and H, as well as linoleic and linolenic acids. After purification, it becomes a usable cosmetic raw material.
Mink oil, like the previous one, is an animal oil rich in vitamins (it is obtained from mink muscles).
In addition to oils, oil from sprouted wheat seeds always contains 2-12% fatty acids. It is well preserved and rich, in particular, in vitamin E, carotene, linoleic and linolenic acids, ergosterol, and also contains small amounts of vitamin K.
The most important natural wax used in the manufacture of gels is beeswax. It is a hard yellow or (when bleached) white viscous substance. Beeswax contains 72% of various natural waxes (wax esters), about 14% of free high-molecular fatty acids, free fatty alcohols, etc.
Carnauba wax is obtained from the leaves of the carnauba palm tree. This is the hardest of natural waxes. It mixes well with many fats, oils, waxes, etc., increasing their melting point and increasing the hardness of the composition.
Wool fat is a fat-like substance obtained from sheep's wool as a result of washing it. When 25% water is added to wool fat, a substance called lanolin is obtained. Raw lanolin is yellow-brown in color, but when purified it is almost white. It contains a large amount of cholesterol (largely esterified with various fatty acids), various waxes, as well as free high-molecular fatty acids and fatty alcohols.
Thus, purified lanolin is quite suitable as a feedstock. In addition, various products are made from it for various purposes, such as lanolin oil and various fractions of lanolin.
All natural fats and oils are triglycerides, i.e. esters of the tribasic alcohol glycerol. There are no fats or oils in nature in which glycerol is esterified with only one fatty acid; Natural fats are always esters of two or more fatty acids.
Animal fats (such as lard) and vegetable fats can be hydrolyzed with water at high temperature and pressure into fatty acids and glycerol. As a result, mainly stearic acid, palmitic acid and myristic acid are obtained. All three acids are solid, waxy substances, colorless and odorless. In this form, they are excellent raw materials for the preparation of creams, gels and various emulsions.
Natural oils, in addition to the above acids, also contain unsaturated fatty acids, such as oleic acid with one double bond, linoleic acid with two double bonds and linolenic acid with three double bonds. Unsaturated fatty acids and their esters are liquid at room temperature. Due to the presence of double bonds in them, they are very sensitive to decomposition reactions, for example, to the action of microbes, and easily break down into smaller molecules, which often have an unpleasant odor. Thus, they spoil quickly. Therefore, they are usually hydrogenated at double bonds, and from all three of the above unsaturated fatty acids, stearic acid is formed; at the same time they all become hard, which is why this method is called fat hardening.
Wax is formed from an ester of a low molecular weight carboxylic acid, such as acetic acid, and a macromolecular so-called fatty alcohol; fatty alcohols are obtained, in particular, by the decomposition of natural waxes. For the preparation of gels, the most important raw materials are stearic alcohol and cetyl alcohol.
These relatively high molecular weight compounds, obtained by processing natural fats and waxes, are widely used in cosmetics. They are waxy or fat-like substances that adhere well to the skin. They easily mix with sebum and create an excellent addition to the base of creams, gels and other products, improving their properties.
As noted earlier, natural fats, oils and waxes are always mixtures containing a large number of different organic compounds. Therefore, depending on the place of origin and other environmental factors, they differ in their composition and properties. Modern industry, however, strives to produce cosmetic products of constant quality, so sustainable synthetic substances have noticeably replaced natural products.
By processing natural fats and waxes, as described above, fatty acids, fatty alcohols and, of course, glycerin necessary for industrial production are obtained. By combining them again synthetically, pure and stable fats and waxes are obtained. According to their origin and manufacturing method, they are called semi-synthetic products.
Synthetic waxes include esters of stearic, palmitic and myristic acids, obtained in large quantities from natural substances. The second component in them is most often isopropyl alcohol.
Silicones represent a very important group of synthetic fatty and waxy raw materials. These substances are based on a chain of alternating silicon and oxygen atoms, to which side organic groups are attached. An example of silicones is silicone oil, which is a relatively low molecular weight derivative of methylsiloxane.
Speaking about the properties of silicones, it should be noted that they are shelf stable and, in addition, are well tolerated by the body. They do not soften with increasing temperature (this is very important for using them as a liquid component of dense cosmetics), mix well with sebum and form a water-repellent film when used generously.
A polyalcohol (polyol) is an organic compound whose molecule contains more than one hydroxyl group OH. Ethylene glycol and glycerol, having two and three OH groups, respectively, are the simplest polyalcohols. This group also includes all sugars and various glycol derivatives, such as polyethylene glycols, which have already been discussed above. In gels, polyalcohols are used as humectants; in this sense, the most important are glycerin, propylene glycol, sorbitol and fructose.
Colloids include a variety of substances of plant and animal origin that form colloidal solutions with water; many of them are polysaccharides. Of the colloids that have a polysaccharide base, the following can be mentioned (Table 2).
Table 2 Colloids having a polysaccharide base
Adhesives are usually products of plant origin. Only a small part of plant adhesives is listed here. Agar-agar, which belongs to the group of alginates, is well known; it is obtained from seaweed and is used to produce gummy-type sweets.
Dextran is produced using certain microorganisms from cane sugar. It is a polymer whose molecular weight ranges between 75,000 and 1,000,000. In addition to being used as a blood plasma substitute, it can be used, for example, to regulate the viscosity of solutions.
Celluloses are a widely used and quite diverse group of substances, of which only three examples are given above. Among the various forms of application for cosmetic purposes, their functions as a viscosity regulator for solutions and as a stabilizer for emulsions are important.
Colloids that have a protein base are, in particular, gelatin, obtained from bones and skins, soy and corn proteins, casein - the protein substance of milk, and albumin, which is obtained from egg whites.
It is characteristic of colloids that they are suitable for forming gels and increasing the viscosity of solutions and emulsions.
Modern emulsion technology uses various types of cellulose, mainly as stabilizers. They are also used as the main component of face masks, as well as in various hair care products.
In addition, protein colloids are used in skin care preparations because they are constructed from amino acid chains of varying lengths and, depending on the processing method, may also contain free amino acids; thus, they can be compared with protein hydrolysates5.
Unsaturated (unsaturated) fatty acids (linoleic, arachidic) are found in fish fat and vegetable oils. They are indispensable for the body, since they are not synthesized, but are very necessary, since they are an active part of cell membranes, reduce cholesterol and prevent its deposition in blood vessels, inhibit fat synthesis, participate in the formation of hormones, improve the condition of the skin and walls of blood vessels, regulate fat metabolism in the liver - which determines the need for daily consumption of vegetable oils.
Saturated acids are in a solid state at room temperature, while unsaturated acids are in a liquid state. Unsaturated acids, unlike saturated acids, easily enter into chemical reactions, stimulate the body's defenses and increase resistance to infectious diseases.
The role of polyunsaturated fatty acids (PUFAs) - arachidonic, linolenic, linoleic, etc., is especially important in the regulation of metabolic processes in cell membranes, as well as in the processes of energy formation in mitochondria. About 25% of the fatty acid composition of the membranes is arachidonic acid. With an abundance of vegetable fats in the diet, the spectrum of unsaturated fatty acids in membranes is richest. The fatty acid composition of cell membranes changes, for example, in infants, depending on feeding with breast or cow's milk. PUFAs are a source of energy in the body: for example, about 60% of the energy in the myocardium is used through the transformation of PUFAs. They play an important role in the mobilization of cholesterol compounds and the prevention of atherosclerosis, as well as in increasing the elasticity of the walls of blood vessels and the metabolic processes of the mucous membranes and skin.
A lack of unsaturated fatty acids in the diet leads to changes in the skin (dryness, peeling, eczema, hyperkeratosis), increases susceptibility to ultraviolet rays, increases the permeability of blood vessels (tendency to rupture capillaries, hematuria), predisposes to the occurrence of ulcerative processes in the gastric mucosa and duodenum, dental caries, arthritis.
The physiological need for PUFAs is 7-9 g for an adult, 3-4 g for children. To satisfy the body's need for these acids, it is enough to consume 15-20 g of sunflower oil per day. It must be taken into account, however, that PUFAs are biologically active only in their pure form. Their oxidation during prolonged heating and high temperature or long-term storage leads to inactivation of linoleic, linolenic and arachidonic acids. Therefore, vegetable oils as a source of fatty acids should be consumed fresh - in salads, vinaigrettes and other snacks.
Repeat. Two fatty acids - omega-3 (linolenic acid) and omega-6 (linoleic acid) are essential. Every cell needs them to reproduce new cells. They affect immunity, energy production, are part of the brain, and if they are deficient, learning ability and memory deteriorate. The daily norm of essential acids is 10-20% of the energy diet. Lecithin fat is necessary for cell membranes, muscle and nerve cells of which they are composed, the liver, and the brain. By dissolving cholesterol in the walls of blood vessels, lecithin helps remove it from the body. Taking lecithin before meals improves the breakdown of fat and the absorption of fat-soluble vitamins.
Fat-like substances, phospholipids
Lipoids also play an important role in the body: phospholipids (especially lecithin) and cholesterol. Phospholipids are a structural part of the membranes of almost all cells; Brain tissue and nerve fibers are especially rich in them. Phospholipids, having lipotropic properties, remove fat from the liver, enhance its emulsification in the intestines during digestion, thus enhancing its absorption.
Phospholipids promote the removal of cholesterol from the body and, therefore, play a positive role in the prevention of atherosclerosis. By participating in the process of energy formation, they have a positive effect on the process of maturation of red blood cells and the accumulation of hemoglobin in them, and contribute to increased activity of the nervous system, in particular the process of excitation.
The physiological need for phosphatides with a balanced diet is 6-7 g per day. The main sources of phosphatides are many foods: vegetable oils (especially unrefined), eggs, cow butter, cheese, etc.
Production for the production of phosphatides for food purposes has been organized. They are used to enrich refined vegetable oils and margarine in the baking and confectionery industries. Phosphatides are used in animal husbandry to increase the biological value of feed.
Fat contains phosphatides. The following have the greatest biological activity: lecithin, cephalin, sphingomyelin:
1) in combination with proteins, they are part of the nervous system, liver, heart muscle, and gonads;
2) participate in the construction of cell membranes;
3) participate in the active transport of complex substances and individual ions into and out of cells;
4) participate in the process of blood clotting;
5) promote better utilization of protein and fat in tissues;
6) prevent fatty liver inflammation;
7) play a role in the prevention of atherosclerosis - they prevent the accumulation of cholesterol in the walls of blood vessels, promoting g 111 breakdown and excretion from the body.
The need for phosphatides is 5-10 g/day.
Among plant products, phosphatides are found in unrefined oils.
STEROLS
Fat contains sterols, water-insoluble compounds. There are phytosterols - of plant origin and zoosterols - of animal origin.
Phytosterols have biological activity in normalizing fat and cholesterol metabolism, preventing the absorption of cholesterol in the intestine, which is of great importance in the prevention of atherosclerosis. They are found in vegetable oils.
Cholesterol is an important zoosterol. It enters the body with products of animal origin, but can also be synthesized from intermediate products of carbohydrate and fat metabolism.
Cholesterol plays an important physiological role, being a structural component of cells. It is a source of bile acid hormones (sex hormones) and the adrenal cortex, a precursor of vitamin D.
At the same time, cholesterol is also considered as a factor in the formation and development of atherosclerosis.
In the blood and bile, cholesterol is retained in the form of a colloidal solution due to binding with phosphatides, unsaturated fatty acids, and proteins.
When the metabolism of these substances is disturbed or their deficiency occurs, cholesterol falls out in the form of small crystals that settle on the walls of blood vessels in the bile ducts, which contributes to the appearance of atherasclerotic plaques in the vessels and the formation of gallstones.
The cholesterol requirement is 0.5 - 1 g/day. Almost all products of animal origin contain cholesterol: brains - 2000 mg%, Ocean pasta - 1000 mg%, chicken and duck eggs - 570 - 560 mg%, hard cheeses - 520 mg%.
Cholesterol is the starting material for the formation of bile acids, sex hormones and adrenal hormones, as well as for the formation of vitamin D3 when exposed to ultraviolet rays on the skin. However, a person does not lack cholesterol, since it is easily formed from various substrates: fat, carbohydrates, amino acids, etc. About 2.5 g of cholesterol is formed in the body per day, and 0.5 g comes from food. Therefore, the reason for the accumulation Excess cholesterol, which plays a role in the development of atherosclerosis, is not exogenous cholesterol, i.e., cholesterol supplied with food, but a violation of its metabolism in the body, excessive formation and slower excretion, which is facilitated by excess consumption of food, especially rich in fat with saturated fatty acids ( palmitic, stearic, capronic, caprylic, etc.), easily digestible carbohydrates (sucrose, fructose, glucose, etc.).
Edible fats
Biological role of dietary unsaturated fatty acids in human nutrition
1. Participate as structural elements of cell membranes.
2. They are part of connective tissue and nerve fiber sheaths.
3. Affect cholesterol metabolism, stimulating its oxidation and release from the body, as well as forming esters with it, which do not fall out of solution.
4. They have a normalizing effect on the walls of blood vessels, increasing their elasticity and strengthening them.
5. Participate in the metabolism of B vitamins (pyridoxine and thiamine).
6. Stimulate the body's defense mechanisms (increase resistance to infectious diseases and radiation).
7. They have a lipotropic effect, i.e. prevent fatty liver.
8. They are important in the prevention and treatment of diseases of the cardiovascular system.
The need for dietary unsaturated fatty acids is 3-6 g/day.
Based on their PUFA content, dietary fats are divided into three groups:
Group 1 - rich in them: fish oil (30% arach.), vegetable oils.
Group 2: with an average content of PUFAs - lard, goose, chicken fat.
Group 3 - PUFAs do not exceed 5 - 6%: lamb and beef fats, some types of margarine.
Overheated fats.
The production of crispy potatoes, fish sticks, frying canned vegetables and fish, as well as the preparation of fried pies and donuts has become widespread in the diet. Vegetable oils used for these purposes are subjected to heat treatment in the temperature range from 180 to 250 °C. When vegetable oils are heated for a long time, the process of oxidation and polymerization of unsaturated fatty acids occurs, resulting in the formation of cyclic monomers, dimers and higher polymers. At the same time, the unsaturation of the oil decreases and oxidation and polymerization products accumulate in it. Oxidation products formed as a result of long-term heating oil, reduce it nutritional value and cause the destruction of phosphatides and vitamins in it.
In addition, this oil has an adverse effect on the human body. It has been established that long-term use of it can cause severe irritation of the gastrointestinal tract and cause the development of gastritis.
Overheated fats also have an effect on fat metabolism.
Changes in the organoleptic and physico-chemical properties of vegetable oils used for frying vegetables, fish and pies usually occur in case of non-compliance with the technology for their preparation and violation of the instructions “On the procedure for frying pies, using deep fat and monitoring its quality”, when the duration of heating the oil exceeds 5 hours, and the temperature is 190 °C. The total amount of fat oxidation products should not exceed 1%.
