Lipids are the most important organic compounds that play a huge role in ensuring the functioning of the body. Without them, it is impossible to imagine more than one process occurring in our body. Lipids are part of cell membranes, create mechanical protection for organs, are precursors of biologically active substances - and this is not the whole list of functions. What are these connections? What are the classification and classes of lipids?

Lipids are water insoluble substances. Most of them are the building blocks of cells, but these substances are also in free form. For transport of lipids in the blood requires special transport systems. Some compounds exist in a complex with albumin proteins.

Most form water-soluble lipoproteins, which are composed of a lipid and apoprotein. Thus cholesterol and its esters, triglycerides and phospholipids are transported. Some of the lipids are involved in the formation of nanoparticles - liposomes.

Classification

Substances of lipid nature are conveniently classified by structural features. Allocate simple and complex. These classes of lipids are hugely different.

Simple differ in that they contain three standard chemical elements - it is oxygen, carbon and hydrogen. This group includes fatty acids, alcohols and aldehydes, as well as waxes and triglycerides.

Complex substances have additional components - sulfur, phosphorus, nitrogen and others. They, in turn, are divided into polar and neutral. Among the polar - phospholipids containing a phosphoric acid residue. They also include sphingolipids, which are derivatives of amino alcohols. Neutral lipids are acylglycerides, sterol esters and ceramides.

What is the difference between biochemistry? Simple lipids include only alcohol and fatty acids, and complex lipids correspond to their name. In addition to alcohol, they contain high molecular weight fats, as well as carbohydrates, residues of phosphoric acid. This is not the only one.

Fat structure

What is the difference between these substances? Biochemistry has studied the structure of their molecules. In saturated fats, all chemical bonds are filled with hydrogen molecules, while unsaturated ones are not. Due to this, their consistency is different - unsaturated, more liquid.

Unsaturated fats can additionally be classified into monounsaturated and polyunsaturated. The first have only one vacancy for hydrogen, and the second - a few, such is their structure.

Monounsaturated fats are found in oils such as olive, canola, and also in fish oil. Polyunsaturated enter the body with sunflower oil, oily fish, nuts.

Lipoproteins

As mentioned above, lipids are insoluble in water and are transported by special transporters. The complex with apoproteins is called lipoprotein. The biochemistry of these substances differs in the density and size of molecules.
  Low-density lipoproteins have the ability to penetrate to the vulnerable walls of blood vessels and start the atherosclerotic process. Substances of high density are called antiatherogenic, as they prevent the development of the disease. That is why the balance between these compounds is important. The table reflects the density difference between these lipoproteins.

Control of these substances is important for the timely prevention of atherosclerosis. Detailed analysis on

When atherogenic fractions are detected, a special diet is prescribed, which depends on the individual characteristics. Its purpose is to reduce the flow harmful products  - sausages, margarine, mayonnaise and so on. People with concomitant obesity should reduce their total calories per day.

Role in the body

What are the values ​​of substances in the body? Lipids are involved in virtually all processes in the body, so their role is not limited to one function. Substances support livelihoods already at the molecular and cellular level.

Structural function

Representatives of this group of substances are phospholipids, which are part of the bilayer of the cell membrane. Thus, lipids are the main structural substance of membranes. Their additional component is cholesterol, which is responsible for the property of fluidity.

Biochemistry has studied that in membranes lipids are located in a special way. The heads of the molecules are hydrophobic and form a layer of the same name, and the tails are hydrophilic. The membrane consists of two layers of lipids, which are attracted by hydrophilic tails. Thus, a kind of barrier is being formed. The hydrophobic layer is of great importance, as it has the property of impermeability to polar compounds and ions.

Thermal insulation and protection

Fat cells accumulate in the subcutaneous tissue of warm-blooded animals, thereby reducing heat loss. Many organs have an additional layer that performs the function of mechanical protection.

Energy function

Regulatory function

The value of lipids is also great for stabilizing all processes. This is due to the fact that lipids form the basis of important molecules. Thus, fat-soluble vitamins A, D, E and K are involved in metabolic and regenerative processes. In addition, vitamin E is responsible for the proper maturation of germ cells, and K ensures the production of plasma clotting factors, responsible for stopping bleeding and maintaining optimal rheology.

Most hormones have a lipid structure (steroid). Also, these substances are part of eicosanoids. Hormones are involved in the regulation of metabolism, sexual function, regeneration. They are carried by blood, due to which they can act distally, that is, far from the place of formation.

Eicosanoids, depending on the mechanism of formation, are divided into prostaglandins, thromboxanes and leukotrienes. All these substances are extremely important - they are involved in the formation of the inflammatory process, blood clotting, regulate arterial pressure  and sexual function, as well as are direct participants in an allergic reaction.

Lipids in the diet

It is important intake of lipids with food. Food products contain mainly triglycerides, which are the most important source of energy. Mandatory supply of saturated fatty acids, which are contained in meat, milk. Unsaturated is also found in vegetable oils, seeds, nuts. Cholesterol, found in animal foods - meat, eggs, butterHowever, you should not use them in excessive quantities.

Meals should be balanced. The optimum ratio of proteins, fats and carbohydrates is 1: 1: 4. Adjustments can be made by a nutritionist individually for each case.

The classification is based on the features of the molecules (structure). All these substances are involved in maintaining homeostasis, that is, constancy, in the body. Without them, existence is impossible. Based on natural lipids, the biochemistry of which has been carefully studied, were synthesized medicationsthat have been successfully applied in therapy.

For example, glucocorticoids, used as anti-inflammatory, anti-allergic and immunosuppressive agents, are based on natural steroids. Currently, they help save the lives of patients, even in emergency situations. There are many such examples. Lipids are indispensable helpers of our body, without which it would not even exist.

Lipid chemistry

Lipids- These are organic substances that are poorly soluble or insoluble in water, but soluble in organic solvents; they are real or potential fatty acid esters.

The content of lipids in the human body averages 10-20% of body weight. Lipids can be divided into two types: protoplasmic and reserve. Protoplasmic (constitutional) are part of all organs and tissues. They make up about 25% of all lipids in the body and almost remain at the same level throughout life. The reserve lipids are stored in the body and their number varies depending on various conditions.

The biological significance of lipids in the body is great. So, they are found in the composition of all organs and tissues. The greatest amount (up to 90%) is contained in adipose tissue. In the brain, lipids make up half the body mass.

Functions of lipids in the body:

Ø Energy  - along with carbohydrates are the main energy cell fuel. When burning 1 g of lipids, 38.9 kJ (or 9.3 kcal) is released.

Ø Structural- lipids (phospholipids, glycolipids) together with proteins are part of biological membranes.

Ø Protective  - the function of mechanical protection, the role of which is performed by subcutaneous fatty tissue.

Ø Thermoregulatory- implementation of this function is carried out due to two aspects: a) fat conducts heat poorly, therefore it is a heat insulator; b) when cooling the body to generate heat due to the release of energy lipids are consumed.

Ø Regulatory- A number of hormones (sex, hormones of the adrenal cortex) are derivatives of lipids.

Ø Lipids are a source of unsaturated higher fatty acids - vitamin F, one of the essential nutritional factors.

Ø Fat is a source of endogenous water in the body. When oxidizing 100 g of lipids, 107 g of water is formed.

Ø Lipids perform the function of natural solvents. They provide the absorption in the intestines of essential fatty acids and fat-soluble vitamins.

Lipid classification

Lipids

Washed neomylye

Simple Complicated Higher Higher

Neutral Fats - Phospholipids alcohols hydrocarbons

Waxes - glycolipids

Sulfolipids

Lipoproteins

All lipids are divided into 2 groups: washed   and untrimmed . Washingcalled the process of formation of salts of fatty acids by alkaline hydrolysis of fat. Soap- These are sodium or potassium salts of fatty acids. Sodium salts are solid soaps, and potassium salts are liquid.

There are two classes of washed lipids: simple  and complicated  lipids. Simple lipids got their name because they consist only of atoms C, H and O. These include two groups of compounds: neutral fats and waxes.

Simple lipids

This group includes substances that are esters of alcohols and higher fatty acids. Of the alcohols in the composition of lipids are: glycerin, oleic alcohol and cyclic alcohol - cholesterol.

Triacylglycerol (TAG)   (triglycerides, neutral fats). They are esters of glycerin and three higher fatty acid molecules. TAG - the main components of apodocytes of adipose tissue, which is a depot of neutral fats in humans and animals.

TAGs have the following structure:

H 2 C - O - C = R

NS - O - C = R 1

H 2 C - O - C = R 2

Since glycerin is a triatomic alcohol, fatty acids can form esterconnectionsin three places. Accordingly, in the tissues of the body are found monoacylglycerides, diacylglyceridesand triacylglycerides.

The carbon atoms in the glycerol molecule are numbered in accordance with the stereochemical nomenclature. There are many different types of triacylglycerides that differ in the nature of the three fatty acid residues attached to the glycerol by the ester bond. If in all three positions there are residues of the same fatty acid, then such triacylglycerides are called simple.In this case, their names are determined by the name of the corresponding fatty acid. Examples of simple triacylglycerides can be tristearoylglycerol (three stearic acid residues in the composition), tripalmitoylglycerol. Triacylglycerides, which contain residues of two or three different fatty acids, are called mixed

The melting point of neutral fats (TAGs) depends on the fatty acid composition. It increases with increasing number and length of fatty acid components. For example, at 20 ° C, tristearin and tripalmitin are solids, and triolein and trilinelein are liquid. It should be noted that triacylglycerides are completely insoluble in water, since they are absent in their composition polar groups.  As for diacyl and monoacylglycerides, they have by polaritydue to the presence of free hydroxyl groups. Therefore, they partially interact with water. Triacylglycerides are soluble in diethyl ether, benzene, chloroform. Most of the neutral fats in the body of animals contain mainly residues of palmitic, stearic, oleic and linoleic fatty acids. The composition of neutral fat from different tissues of the same organism can vary significantly. So, subcutaneous fathuman is richer in saturated fatty acids than liver fat, which contains more unsaturated fatty acids.

The fats of butter and milk contain the highest amount of short-chain fatty acids.

Fatty acid   - These are aliphatic carboxylic acids. They serve as a kind of building blocks for most lipids. Currently, over 70 fatty acids have been isolated from living organisms. They can be divided into two groups: 1) saturated  fatty acids and 2) unsaturated  fatty acid.

From saturated fatty acids  in the body are more common palmitic, stearicand, less commonly, lignocerol, have 24 carbon atoms. Fatty acids containing 10 or less carbon atoms are rarely found in animal lipids. Of unsaturated fatty acids Acids consisting of 18 carbon atoms are most widely represented in the body. These include oleic  (has one double bond), linoleic(two double bonds) linolenic(three double bonds) and arachidonic  (has four double bonds) acids. Linoleic and linolenic in the body are not synthesized , and therefore they are among the indispensable factors of nutrition and should regularly come from food - vegetable oils, where they make up to 95%.

In human fats, palmitic, myristic and lesser amounts of stearic acid prevail, and of unsaturated ones, oleic, linoleic and linolenic acids prevail.

Physico-chemical properties of lipids are determined by the properties of their constituent fatty acids. Thus, saturated fatty acids have a high melting point and, accordingly, animal fats, consisting mainly of these acids, melt with more high temperature. Fats in which unsaturated acids (vegetable oils) predominate have a lower melting point. Fatty acid unsaturation significantly affects their properties. With an increase in the number of double bonds, the melting point of fatty acids decreases, their solubility increases in non-polar solvents and they react more easily than saturated ones. So, unsaturated acids can attach different atoms at the place of double bonds. In the body, oleic acid having a double bond adds two hydrogen atoms and turns into stearic acid. All unsaturated fatty acids found in nature are liquid at room temperature.

Prostaglandids  - These are derivatives of fatty acids with 20 carbon atoms, incorporating a cyclopentane ring. Prostaglandins are found in all mammalian tissues and have diverse biological effects. Currently, several groups of prostaglandins are known: A, B, E, F, I, D, H, G. Among them, prostaglandins F 2 and F 2α predominate, the precursor of which is arachidonic acid. In humans, all cells and tissues, with the exception of red blood cells, synthesize prostaglandins.

The mechanism of action of prostaglandins on cells is not fully understood. The biological effect of prostaglandins in the body is as follows:

• Effect on the cardiovascular system - an increase in blood flow through the general expansion of blood vessels with a decrease in peripheral resistance. In addition, prostaglandins regulate platelet aggregation (group F prostaglandins accelerate, and group I inhibit).
• Effect on water and electrolyte metabolism. All prostaglandins enhance the ion flux through the membranes of epithelial cells.
• Effect on the nervous system. Prostaglandins have a sedative and tranquilizing effect, are antagonists of anticonvulsants.
• Effect on the gastrointestinal tract. Prostaglandins inhibit the secretion of the stomach and pancreas, increase intestinal motility.
• Impact on the reproductive system.

Prostaglandins are involved in the inflammatory process, increasing it in the inflammatory focus. Inhibitors of the formation of prostaglandins are acetylsalicylic acid and other salicylates. Aspirin inactivates an enzyme that catalyzes the conversion of arachidonic acid to prostaglandins. This explains the anti-inflammatory effect of aspirin.

Waxes - These are esters of fatty acids and higher monohydric or dihydric alcohols. The number of carbon atoms in such alcohols ranges from 16 to 22. These are solid substances that mainly perform protective functions. The waxes are the so-called natural waxesi.e. those synthesized by living organisms (beeswax; lanolin - wax, which is part of the fat, covering wool; wax, covering the leaves of plants).

Complex lipids

The complex lipids class includes groups of compounds: phospholipids, glycolipids and sulfolipids, lipoproteins.

Phospholipids - complex lipids containing phosphorus. In addition to phosphoric acid in their molecules are alcohols, fatty acids, nitrogenous bases and some other compounds. Phospholipids are important for the body: they form the basis of biological membranes, are found in large quantities in the nervous tissue (brain tissue is 60-70% composed of phospholipids), there are many of them in the liver and heart.

Depending on the alcohol they contain, they are subdivided into glycerophospholipids and sphingophospholipids. The root "phospho" in these names indicates that the composition of all substances of these groups includes the residue of phosphoric acid.

Glycerophospholipids. The general structural formula of glycerophospholipids includes the alcohol residue — glycerin, whose hydroxyl groups on the first and second carbon atoms form ester bonds with fatty acids. The hydroxyl group at the third carbon atom forms an ester bond with residues of phosphoric acid. Usually, some nitrogen-containing substance (choline, serine, ethanolamine) is attached to the phosphoric acid residue. The general formula of glycerophospholipids is as follows:

H 2 C - O - C = O

NA - O - C = O

H 2 C - O - P - O - R 3

The simplest glycerophospholipid is phosphatidic acid. In the tissues of the body, it is contained in small quantities, however, it is an important intermediate in the synthesis of triacylglycerides and phospholipids. Most widely represented in the cells of various tissues phosphatidylcholine   (lecithin) and phosphatidylethanolamine (kefalin) They have the amino alcohols, choline and ethanolamine, attached to the phosphoric acid residue. These two glycerophospholipids are metabolically closely related to each other. They are the main lipid components of most biological membranes. There are other glycerophospholipids in the tissues. In phosphatidylserine, phosphoric acid is esterified with a hydroxyl group of serine, and in phosphatidylinositol, with a six-atomic alcohol, with inositol.

Phosphatidyl inositol derivative - phosphatidyl inositol-4,5-bisphosphate is an important component of biological membranes. When stimulated by the corresponding hormone, it splits. Its cleavage products (diacylglyceride and ipozitol triphosphate) serve as hormone-acting intracellular messengers.

Glycerophospholipids are metabolically very closely related lysophospholipids.Their composition contains only one fatty acid residue. An example is lysophosphatidylcholine, which plays an important role in the metabolism of phospholipids.

Sphingophospholipids. They contain in its composition dihydric unsaturated alcohol sphingosine.

A representative of this group of compounds, widespread in the body is sphingomyelin. It consists of sphingosine, a fatty acid residue, a phosphoric acid residue, and choline. Sphingomyelin is found in the membranes of plant and animal cells. The nervous tissue, in particular the brain, is especially rich in sphingophospholipids.

The role of phospholipids:

Ø Participate in the formation of membranes.

Ø Influence membrane functions - selective permeability, realization of external effects on the cell.

Ø Form a hydrophilic membrane of lipoproteins, promoting the transport of hydrophobic lipids.

A characteristic feature of phospholipids is their diphilicitythat is, the ability to dissolve both in the aquatic environment and in neutral lipids. This is due to the presence of pronounced polar properties of phospholipids. At pH 7.0, their phosphate group always carries a negative charge.

The serine residue in the phosphatidylserine molecule contains alpha-amino and carboxyl groups. Therefore, at pH 7.0, the phosphatidylserine molecule has two negative and one positively charged groups and carries a total negative charge. At the same time, the fatty acid radicals in the phospholipid composition do not have an electrical charge in an aqueous medium and thus are a hydrophobic part of the phospholipid molecule. The presence of polarity due to the charge of the polar groups causes hydrophilicity. Therefore, at the interface between oil and water, phospholipids are arranged in such a way that the polar groups are in the aqueous phase, and the non-polar groups are in the oil phase. Due to this, in the aquatic environment they form a bimolecular layer, and when a certain critical concentration is reached, micelles.

The participation of phospholipids in the construction of biological membranes is based on this. The treatment of diphilic lipid in an aqueous medium with ultrasound leads to the formation of liposomes. Liposome - a closed lipid bilayer, inside of which is part of the aquatic environment. Liposomes are used in the clinic, cosmetology as a kind of container for the transfer of drugs, nutrients to certain organs and for the combined action on the skin.

Glycolipids - These are sphingolipids containing carbohydrates.

Glycolipids are widely distributed in tissues. They are especially rich in the myelin sheaths of the nerves. The composition of glycolipids includes alcohol - sphingosine. Glycolipids do not contain phosphoric acid. Their molecules have polar, hydrophilic carbohydrate groups (most often D-galactose).

There are two groups of glycolipids: cerebrosides and gangliosides.

Cerebrosides:the molecule contains an alcohol, sphingosine, linked by an ester bond to a fatty acid residue (nerve, cerebronic, lignoceric) - this complex is called ceramide. The carbohydrate portion of cerebroside is represented by D-galactose, which is attached to sphingosine. Fatty acids found in cerebrosides are unusual in that they contain 24 carbon atoms. More common nerve, cerebronand lignocericacid. The composition of cerebrosides of other tissues (except nervous tissue) instead of galactose may include glucose.

Gangliosideshave a complex structure. The structure of the molecule in addition to sphingosine, includes an oligosaccharide containing residues of glucose and galactose, as well as one or more molecules sialic acids  (derivatives of amino sugars).

Sialic acid - these are amino sugar derivatives. N-acetylglucosamine and N-acetylneuramic acid are dominant in the gangliosides.

Gangliosides are usually found on the outer surface of cell membranes, especially the nervous one.

Cerebroside and ganglioside distribution in the brain tissue was noted. If the white matter is dominated by cerebrosides, the gray matter is gangliosides.

Sulfolipids - These are glycolipids containing a sulfuric acid residue.

Sulfolipids (sulfatides) have a structure similar to cerebrosides, with the only difference that at the 3rd carbon atom of galactose, the residue of sulfuric acid is attached instead of the hydroxyl group.

Lipoproteins - complexes of lipids with proteins. The structure is small spherical particles, the outer shell of which is formed by proteins (which allows them to move through the blood), and inner part  - lipids and their derivatives. The main function of lipoproteins is lipid blood transport. Depending on the amount of protein and lipids, lipoproteins are divided into chylomicrons, very low density lipoproteins (VLDL) - pre-β-lipoproteins, low density lipoproteins (LDL) - β-lipoproteins, and high-density lipoproteins (HDL) –α-lipoproteins.

Neodymy lipids

Neodymy lipids   not hydrolyzed with alkali to release fatty acids. There are two main types of unsaponifiable lipids - higher alcoholsand   higher hydrocarbons.

Higher alcohols

To higher alcohols include cholesterol  and fat soluble vitamins  - A, D, E and F.

Sterols- is a group of high molecular weight cyclic alcohols, which form esters with steric acids with fatty acids. The sterol representative is cholesterol(monatomic cyclic alcohol), first isolated from E. Conradi's gallstones in the 17th century.

Cholesterol it is a derivative of cyclopentan perhydrophenanthrene containing three fused cyclohexane rings with which a cyclopentane ring is attached.

Cholesterol is a crystalline water-insoluble substance that can dissolve in organic solvents.

Cholesterol is found in all cells of the body. Cholesterol is one of the main components of the plasma membrane and lipoproteins of the blood plasma, often in the body in esterified form  (in the form of fatty acid esters) and serves as the starting compound for the synthesis of all steroids that function in the body (adrenal cortex hormones, sex hormones, vitamin D 3). No cholesterol found in plants.

In the body, cholesterol performs important functions:

Ø It is the precursor of many biologically important compounds: bile acids, steroid hormones, vitamin D, glucocorticoids and mineralocorticoids;

Ø Included in the cell membrane;

Ø Increases red blood cell resistance to hemolysis;

Ø Serves as a kind of insulator for nerve cells, providing conduction of nerve impulses.

Higher hydrocarbons

Higher hydrocarbons are derivatives of isoprene. Among the lipid components that are found in cells and a relatively small amount are terpenes. Their molecules are built by combining several molecules of a five-carbon hydrocarbon - isoprene. Terpenes containing two isoprene groups are called monoterpenes, and those containing three are called sequiterpenes.

In plants, a large number of mono-and sekviterpenov. Many of them give the plants their characteristic aroma and serve as the main components of the fragrant oils obtained from such plants. Carotenoids (precursors of vitamin A) belong to the group of higher terpenes. Natural rubber is a polyterpene.

Most people eat quite varied, and all the necessary lipids enter their bodies. It should be noted that some of these substances are synthesized cookies  that partly compensates for their lack of food. However, there are irreplaceable lipids, or rather their components - polyunsaturated fatty acid  . If they do not enter the body with food, over time this will inevitably lead to certain disorders.

Most of the lipids in food are consumed by the body to produce energy. That is why when fasting  man loses weight and weakens. Deprived of energy, the body begins to expend lipid reserves from subcutaneous fatty tissue.

Thus, lipids play a very important role in healthy eating  person However, for some diseases or disorders, their number should be strictly limited. Patients usually find out about this from the attending physician ( usually, gastroenterologist  or nutritionist ).

The energy value of lipids and their role in the diet

In terms of energy release, the greatest role is played triglycerides  . Saturated acids that make up these substances are absorbed by the body by 30 - 40%. Monounsaturated and polyunsaturated fatty acids are completely absorbed by a healthy organism. A sufficient intake of lipids allows the use of carbohydrates and proteins for other purposes.

Plant and animal lipids

Examples of sources of lipids of plant and animal origin

  Each source of lipids has certain advantages and disadvantages. For example, animal fats contain cholesterol  which is not in products of plant origin. In addition, animal products contain more lipids, and it is more profitable to use them from an energy point of view. At the same time, an excess of animal fat increases the risk of developing a number of diseases associated with lipid metabolism in the body ( atherosclerosis , cholelithiasis  and etc.). In plant foods, there are less lipids, but the body cannot synthesize them on its own. Even a small amount of  seafood, citrus or nuts supplies enough polyunsaturated fatty acids that are vital to humans. At the same time, a small proportion of lipids in plants can not fully cover the energy costs of the body. That is why in order to maintain health, it is recommended to make the diet as diverse as possible.

What is the body's daily lipid requirement?

The following factors can influence the body's need for lipids:

• Body weight.  Overweight people have to spend more energy. If they are not going to lose weight, then the need for calories and, accordingly, in lipids will be somewhat higher. If they seek to lose weight, then limit, in the first place, it is necessary fatty foods.
• Load during the day.  People performing heavy physical workor athletes need a lot of energy. If an average person has 1500 to 2500 calories, then for miners or loaders, the rate can go up to 4500 to 5000 calories per day. Of course, the need for lipids is also increasing.
• The nature of power.  Every country and every nation has its own traditions in nutrition. Calculating the optimal diet  It is necessary to take into account exactly which products a person usually consumes Some peoples fat food is a kind of tradition, while others, on the contrary, are vegetarians  and their lipid consumption is minimized.
• The presence of concomitant pathologies.  For a number of disorders, lipid intake should be limited. First of all, we are talking about diseases of the liver and gallbladder, since these organs are responsible for the digestion and absorption of lipids.
• The age of the person.  AT childhood  the metabolism is faster and the body requires more energy for normal growth and development. In addition, children usually do not have serious problems with the gastrointestinal tract, and they are well assimilated to any food. It should also be borne in mind that babies  get an optimal set of lipids with breast milk  . Thus, age greatly affects the rate of fat intake.
• Floor.  It is believed that on average, a man consumes more energy than a woman, so the rate of fat in the diet of men is slightly higher. However, in pregnant women, the need for lipids increases.

Independently it is difficult for a person to make the necessary calculations and take into account all the factors for the selection of an optimal diet. To do this, it is better to consult a dietitian or food hygiene specialist. After a brief survey and clarification of the nature of the diet, they will be able to create an optimal daily diet, which the patient will adhere to in the future. They can also recommend specific foods that contain the necessary lipids.

What foods contain mostly lipids ( milk, meat, etc.)?

The amount of lipids in a particular product is usually indicated on the product packaging in the “ the nutritional value". Most manufacturers are obliged to inform consumers about the mass fraction of proteins, carbohydrates and fats. In self-prepared food, the amount of lipids can be calculated using special tables for nutritionists, which list all the main products and dishes.

Mass fraction of lipids in basic foods

  In most products of plant origin ( vegetables, fruits, greens, root vegetablesa) the mass fraction of fat is not more than 1 - 2%. The exceptions are citrus fruits, where the proportion of lipids is slightly higher, and vegetable oils, which are a lipid concentrate.

Are there essential lipids and what are their most important sources?

Most of the essential lipids are found in foods of plant origin. These are monounsaturated and polyunsaturated fatty acids. The cells of the body cannot synthesize these compounds, since the metabolism in animals is very different from that in plants.

Essential fatty acids and their main sources of nutrition

  For a long time, the above fatty acids were equated in importance for the body to vitamins  . Adequate intake of these substances strengthens immunity  , accelerates cell regeneration, reduces inflammatory processes, contributes to the conduction of nerve impulses.

What leads to a lack or excess of lipids in the diet?

Possible effects of lipid imbalance in the diet

Blood and plasma lipids

Triglycerides

Free fatty acids

Cholesterol

In humans, cholesterol performs the following functions:

• stiffens the cell membrane;
• takes part in steroid synthesis hormones ;
• part of the bile;
• participates in learning vitamin d ;
• regulates the permeability of the walls of some cells.

Lipoproteins ( lipoproteins) and their fractions ( low density, high density, etc.)

All blood lipoproteins are divided into several classes, each of which has its own characteristics. The main criterion for distinguishing lipoproteins is their density. According to this indicator, all these substances are divided into 5 groups.

There are the following classes ( fractionsa) lipoproteins:

• High density. HDL) are involved in the transfer of lipids from body tissues to the liver. From a medical point of view, they are considered useful, as due to their small size they can pass through the walls of blood vessels and “clean” them from lipid deposits. Thus, a high level of HDL reduces the risk of atherosclerosis.
• Low density. LDL) transport cholesterol and other lipids from the liver ( places of their synthesis) to the tissues. From a medical point of view, this fraction of lipoproteins is harmful, since it is LDL that contribute to the deposition of lipids on the walls of blood vessels with the formation of atherosclerotic plaques. High level  LDL greatly increases the risk of atherosclerosis.
• Medium ( intermediate) density. Intermediate density lipoproteins ( Lpp) do not have a significant diagnostic value, as they are an intermediate product of lipid metabolism in the liver. They also transfer lipids from the liver to other tissues.
• Very low density. Lonp) transfer lipids from the liver to the tissues. They also increase the risk of atherosclerosis, but in this process play a secondary role ( after LDL).
• Chylomicrons.  Chylomicrons are significantly more than other lipoproteins. They are formed in the walls of the small intestine and transfer lipids from food to other organs and tissues. In the development of various pathological processes, these substances do not play a significant role.

Lipid analysis

What is a lipid profile?

Lipidogram includes tests for the determination of the following blood lipids:

• Cholesterol.  This indicator does not always depend on lifestyle and nutrition. A significant part of cholesterol in the blood is the so-called endogenous cholesterol, which is produced by the body itself.
• Triglycerides.  Triglyceride levels usually increase or decrease in proportion to cholesterol levels. It may also increase after eating.
• Low density lipoproteins ( LDL). The accumulation of these compounds in the blood greatly increases the risk of atherosclerosis.
• High density lipoproteins ( HDL).   These compounds are able to "clean" the vessels of excess cholesterol and are beneficial for the body. Low level  HDL suggests that the body does not digest fats.
• Very low density lipoproteins ( Lonp).   They have a secondary diagnostic value, but their increase together with an increase in LDL levels usually indicates atherosclerosis.

Before donating blood to a lipid profile, you should follow a few simple rules. They will help avoid significant fluctuations in blood lipids and make the results more reliable.

Before passing the analysis, patients should consider the following recommendations:

• It is possible to eat in the evening before the analysis, but you should not abuse fatty foods. It is better to adhere to the usual diet.
• The day before the analysis, it is necessary to exclude various kinds of load ( both physical and emotional), as they can lead to the breakdown of the body's fatty tissue reserves and an increase in the level of lipids in the blood.
• In the morning, just before donating blood, do not to smoke.
• Regular intake of a number of drugs also affects the level of lipids in the blood ( contraceptive drugs  , hormonal drugs, etc.). It is not necessary to cancel them, but this fact must be taken into account when interpreting the results.

Normal blood lipid levels

Diseases associated with lipid metabolism

Disorders of lipid metabolism ( dyslipidemia)

An imbalance of lipids can lead to the following pathologies:

• atherosclerosis ( consequently - aneurysm , hypertension  or other problems with the cardiovascular system);
• skin problems;
• problems with the nervous system;
• a number of pathologies of the gastrointestinal tract ( pancreatitis  , gallstone disease, etc.).

Causes of high and low lipid levels

Pathological conditions associated with changes in the amount of lipids in the blood are called dyslipidemia. They are also divided into several types. If the blood levels of triglycerides are elevated, they speak of hypertriglyceridemia ( synonym - hyperlipemia). If the level of cholesterol rises, they talk about hypercholesterolemia.

Also, all dyslipidemias by origin are divided into the following groups:

• Primary.  By primary dyslipidemia mainly mean genetic diseases and abnormalities. As a rule, they are manifested by an excess or lack of any enzymes  that violates lipid metabolism. As a result, the amount of these substances in the blood decreases or increases.
• Secondary. Under the secondary dyslipidemia mean pathological conditions in which the increase in lipids in the blood is a consequence of some other pathology. Thus, it is necessary to treat, first of all, this particular pathology, then the level of lipids gradually stabilizes.

There are five main types of primary hyperlipoproteinemia ( elevated lipoprotein levels):

• Hyperchilomycronemia.  With this disease, the level of triglycerides increases in the blood, while the level of other lipids usually remains within the normal range. Patients may experience paroxysmal stomach ache  but without the tension of the abdominal muscles. Xanthomas may appear on the skin ( brown or yellowish formations). The disease does not lead to the development of atherosclerosis.
• Familial hyper-beta lipoproteinemia.  With this pathology, the number of beta-lipoproteins, and sometimes prebeta-lipoproteins, increases. The analysis significantly exceeded cholesterol levels. The amount of triglycerides may be normal or slightly increased. Patients also appear xanthomatosis ( xanthomas on the skin). Significantly increased risk of atherosclerosis. With this disease, myocardial infarction is possible even at a young age.
• Familial hypercholesterolemia with hyperlipemia.  Blood levels of both cholesterol and triglycerides are significantly elevated. Xanthomas are large and appear after 20 - 25 years. Increased risk of atherosclerosis.
• Hyper-pre-beta lipoproteinemia.  In this case, the level of triglycerides increases, and the level of cholesterol remains within the normal range. The disease is often combined with diabetes mellitus, gout  or obese.

There are also secondary ( symptomatic) hyperlipoproteinemia in the following diseases:

• Diabetes.  In this case, an excess of lipids in the blood is due to the transformation of excess carbohydrates.
• Acute pancreatitis.  With this disease, the absorption of lipids is violated, and their blood level increases due to the breakdown of adipose tissue.
• Hypothyroidism.  The disease is caused by a lack of hormones. thyroid gland  , which regulate the exchange of lipids in the body.
• Intrahepatic cholestasis and other liver pathologies.  The liver is involved in the synthesis of most lipids needed by the body. With various hepatitis, disorders of bile outflow and other pathologies of the liver and bile ducts, the level of lipids in the blood may increase.
• Nephrotic syndrome.  This syndrome develops with the defeat of the glomerular apparatus. kidney  . Patients with severe renal edema. The level of proteins in the blood decreases, and the level of cholesterol increases significantly.
• Porphyria.  Porphyria is a disease with a hereditary predisposition. In patients, the metabolism of a number of substances is disturbed, as a result of which porphyrins accumulate in the blood. In parallel, lipid levels may increase ( sometimes significantly).
• Some autoimmune diseases.  In autoimmune diseases, the antibodies produced by the body attack their own cells. In most cases, chronic inflammatory processes develop that are associated with an increase in lipid levels.
• Gout.  When gout in the body is disturbed exchange uric acid  and it accumulates in the form of salts. In part, this is reflected in lipid metabolism, although their level in this case is slightly elevated.
• Alcohol abuse.  Alcohol abuse leads to abnormalities of the liver and gastrointestinal tract. A number of enzymes that increase the level of lipids in the blood can be activated.
• Acceptance of some medications.  Long-term oral intake can result in increased lipid levels. contraceptives (contraceptives). Most often about this side effect  mentioned in the instructions for the corresponding drug. Before taking the test, these drugs should not be taken or should be warned about this by the radiating doctor so that he correctly interprets the results of the analysis.

Also elevated levels of lipoproteins in the blood can be observed when of pregnancy  . This increase is usually negligible. With an increase in the level of lipids in 2 - 3 times higher than normal, it is necessary to consider the probability of pregnancy in combination with other pathologies that cause an increase in the level of lipids.

What diseases of the digestive system are associated with lipid metabolism?

Atherogenic lipids are those substances that lead to the development of atherosclerosis. It should be noted that the division of lipids into atherogenic and non-atherogenic is very conditional. In addition to the chemical nature of substances, many other factors contribute to the development of this disease.

Atherogenic lipids often lead to the development of atherosclerosis in the following cases:

• intense smoking;
• heredity;
• diabetes;
• overweight ( obesity);
• sedentary lifestyle ( hypodynamia ) and etc.