Fat enters the body with food, and is also formed from carbohydrates and in a small amount from proteins. The composition of food fats is different, they have different melting points: butter 28-33 ° C, lamb fat 44-51 ° C, bovine fat 41-49 ° C, lard 36-46 ° C, chicken fat 33-40 ° C , goose fat 26-34 ° C. Fats, solid at room temperature, contain many saturated fatty acids (stearic, palmitic, butyric, etc.). The more unsaturated fatty acids in the fat, the lower the melting point of the fat. Human fat is significantly different from the fat that enters the body; it melts at 17.5°C. The composition of human fat depends on nutrition and approaches that of dietary fat if a person feeds exclusively on this dietary fat for a long time.
After absorption and synthesis, fats and fat-like substances (lipoids) are part of the cytoplasm and cell wall.
Some tissues and organs, such as nervous tissue, adrenal glands, contain especially a lot of fat and lipoids. The fat used as a plastic material is strongly associated with cellular structures. In addition, fat is deposited as a reserve material in the adipose tissue surrounding internal organs, such as the kidneys, as well as in the omentum and subcutaneous tissue. The amount of fat in the body is 10-20%. and significantly more in obesity. The fat reserve is used as an energy material, especially if the body is starving. Reserve fat under the action of lipase is converted into glycerol and fatty acids and then oxidized to carbon dioxide and water, releasing a large amount of energy. With severe physical work up to 80% of all energy is released during the breakdown and oxidation of stored fat. Part of the glycerol and fatty acids formed from the reserve fat is converted into glycogen in the liver. Unsaturated fatty acids (oleic, linoleic, linolenic, etc.) found in vegetable fats (especially sunflower and hemp) are converted into lipoids in the liver. The most physiologically valuable arachidonic acid is almost not contained in vegetable oils. It is formed in the body from linoleic and linolenic acids and is found in freshly milked milk and butter. Its daily dose is 5 g. An increase in the amount of fat in the blood by more than 1% is referred to as lipemia.
Easily digested fats of milk, more difficult lamb and pork. Solid animal fats and liquid vegetable oils do not differ in nutritional value if their calorie content is the same; the physiological value of vegetable fats is higher than that of animals. A lack of unsaturated fatty acids in the diet is detrimental to health, causes dryness and inflammation of the skin, reduces the ability of adults to reproduce, and, as expected, by disrupting cholesterol metabolism, contributes to the development of arteriosclerosis. The content of unsaturated linoleic acid in vegetable oils is more than 50%, for example, in sunflower oil about 60 mg%, in corn oil - 55 mg%, and in animal fats - up to 15 mg%, in butter less than 5 mg%. An adult needs 5-10 g of unsaturated fatty acids per day.
Fats should make up about 30% of the total caloric intake of an adult's daily diet, which is equal to 80-100 g of fat.
Lipoids and their meaning. There are 2 main groups of lipoids: phosphatides, or phospholipids, and sterols.
Phosphatides. They contain choline, which contains nitrogen. There are especially many glycerophosphatides in the body. Phosphatides, neutral fats, cholesterol and other lipids are part of cell membranes and cell organelles, causing their selective permeability. Phosphatides are also involved in the reproduction and regeneration of cells and in tissue respiration and are part of the myelin sheaths of nerve cells, in which they are little updated. In addition, another part of the phosphatides is involved in the metabolism in the central nervous system, defining functional state brain. They are also involved in the absorption and synthesis of fat in the intestines, in the transfer of fats in the blood. With the participation of enzymes, phosphatides are synthesized in the intestinal wall, their synthesis in the liver is especially high. The lack of phosphatides in food leads to arteriosclerosis and fatty liver.
In those human tissues where there is an intensive metabolism (brain, liver, kidneys, heart muscle), choline phosphatides, derivatives of neutral fats - lecithins, are widespread. In blood plasma, out of a total amount of phosphatides, equal to an average of 200 mg%, approximately 50-60% are lecithins, and in erythrocytes - 20%. The content of lecithins in different organs varies greatly depending on age, food composition, metabolic rate, and level of functioning. An increase in the activity of the organ and the action of hormones on it increases the content of lecithins in it. In the brain, the exchange of lecithins occurs faster and the age-related fluctuations in the content of lecithins are much less than in other organs. Choline is formed from lecithin, which, when combined with acetic acid, turns into acetylcholine. Acetylcholine is a very active substance involved in many physiological processes.
The importance of acetylcholine as a mediator of the nervous process is especially great. It is believed that it also performs the function of a local hormone in many tissues. Lecithin neutralizes the negative properties of cholesterol. It reduces the content of cholesterol in the blood. In butter, the content of lecithin is the same as in blood. Milk contains 20 times more lecithin than cholesterol. A lot of lecithin is found in egg yolk, brain and liver. The daily dose of phosphatides in an adult is 10 g.
Sterols. Cholesterol is the most abundant in the body. The human body contains an average of 0.2% cholesterol, for 70 kg of body weight - an average of 140 g of cholesterol, with fluctuations from 105 to 175-200 g. There is less cholesterol in a young body, more in an elderly one. The greatest amount of cholesterol in the adrenal glands and in the brain. Each organ contains a certain amount of free and bound cholesterol. In the blood of a healthy person, there is usually 80 mg% free cholesterol and 110 mg% associated with fatty acids. The relative content of cholesterol in tissues does not depend on age. In the body, cholesterol and other sterols are synthesized from the activated form of acetic acid, formed from the products of oxidation of carbohydrates and fats. The main site of its synthesis is the liver.
In the body of a healthy adult, about 80% of cholesterol is formed in the liver, and 20% comes from food. With a mixed diet, food contains no more than 0.5 g of cholesterol per day. The synthesis of cholesterol in the liver increases with a decrease in its content in food, and vice versa. It is not found in plant foods. In a healthy person, the amount of cholesterol introduced with food and synthesized corresponds to the amount of cholesterol excreted from the body.
In the body, cholesterol forms substances that are similar in composition to cholesterol and are of great importance. These include bile acids, sex hormones, and hormones from the adrenal cortex.
Vitamin D is one of the sterols that enter the body with food.
Substances that prevent fatty liver are called lipotropic. These include: the amino acid methionine, vitamins - choline, inositol, B9, B12 lecithin.
The fight against excess adipose tissue, both in medicine and in sports, in terms of its intensity and material costs, can only be compared with the struggle for space exploration. Hundreds of medicines, thousands of types of dietary products are produced, and things are still there. The number of fat people, despite any economic shocks, not only does not decrease, but is constantly growing. Obesity is too complex a problem and deserves separate consideration. Let's just say that carnitine in this case opened up a whole era of new drugs to combat excess adipose tissue. What is human fat? Its chemical composition is relatively simple. For the most part, the subcutaneous (and not only) fat layer consists of triglycerides - esters of glycerol with long-chain fatty acids. In the human body there is a so-called "spontaneous lipolysis". Fat molecules break down at a constant rate and some fatty acids and glycerol enter the bloodstream. Approximately the same amount of fatty acids and glycerol comes from the blood into the subcutaneous fat. All weight loss drugs in the "pre-carnitine era" acted on the body only in this way: the breakdown of fat molecules increased, the blood was filled big amount fatty acids and glycerol. At the same time, fat synthesis remained unchanged, since the ability of fatty acids to penetrate into the cells of the body (including fatty acids) is strictly limited. Fat burning in the body also remains unchanged due to poor penetration of fatty acids into the cell. We know that burning fat provides twice as much energy as burning carbohydrates or proteins, however, fatty acids are very poorly oxidized and, as a result, the use of fat for energy needs of the body is limited. The ability of fatty acids to penetrate into the cell depends almost 100% on the state of a special kind of proteins, "channel proteins" in the cell membrane. The flooding of the blood with fatty acids is accompanied by a mass of negative effects: body temperature rises, nervous excitability increases, tachycardia appears, etc. It should also be noted that fatty acids, oxidized in the body, form highly toxic compounds known as "free radicals", which cause damage to all cell membranes and, as a result, damage to all organs and systems of the body without exception. Free radical oxidation of cell membranes is one of the main causes of aging. He is also credited with a leading role in the development of diseases such as cancer and atherosclerosis. The conclusion is obvious - stimulation of the breakdown of fats in the body is a dead end path. The unique feature of carnitine is that it increases the permeability of cell membranes for fatty acids. Without increasing the rate of breakdown of adipose tissue, it increases the absorption of fat by the body for energy purposes and, as a result, slows down the rate of synthesis of neutral fat molecules in subcutaneous fat depots. With the start of taking carnitine, a persistent loss of adipose tissue begins at a constant rate, which sometimes reaches 10-15 kg within a month without changing the diet. At the same time, the efficiency of fat oxidation in the body sharply increases, since now fatty acids do not give toxic free radicals, but energy stored in the form of ATP. The ability of carnitine to destroy adipose tissue is largely due to the presence of highly mobile methyl (-CH3) radicals in its molecule. The energy of the heart muscle is especially improved, because the heart is fed by 70% fatty acids. Increased penetration of long-chain fatty acids into the cell, followed by oxidation, significantly increases the strength and endurance of the heart muscle. The content of protein in the heart muscle increases and, especially significantly, the content of glycogen. Carnitine is indispensable in cases where it is necessary to increase general and special endurance in aerobic sports (running, swimming, rowing, etc.). If the athlete is not concerned about weight loss, the maximum increase in energy can be achieved by combining carnitine with an increased amount of fat in the diet. There is a special high-fat diet, which is prescribed simultaneously with large doses of carnitine. This method of enhancing bioenergetics is especially preferable when it is necessary to avoid a drop in body weight during training. The energizing effect of carnitine, coupled with its anabolic effect, is highly beneficial for the liver. The liver enhances its detoxification and protein-synthetic function. The content of glycogen in the liver increases. The liver begins to more actively break down lactic and pyruvic acids, which are "fatigue toxins". Thus, carnitine helps to increase endurance in both aerobic and anaerobic (powerlifting, bodybuilding, etc.) sports. If we consider the action of carnitine at the subcellular level, we will see that it affects mainly the mitochondria, which are the "energy stations" of the cell. It is mitochondria that give cells energy, burn fats, proteins and carbohydrates. The mitochondria of the heart work especially intensively, processing fatty acids, and the mitochondria of the liver, which supply the entire body with energy. The main factor limiting muscle growth is the protein-synthetic function of muscles. For an adequate muscle growth sufficient supply of building material - amino acids is necessary. However, no less significant is the energy supply - the supply of energy necessary for protein synthesis. Many scientists believe that it is the energy supply that is the limiting factor in muscle growth, a factor even more important than the influx of building material. In evolutionary terms, mitochondria are the "youngest" organs of the cell. Therefore, in any adverse situation, their work is disrupted in the first place. In any disease, energy metabolism is the first to suffer. Carnitine in this case is something like a philosopher's stone, a cure for all diseases. After all, by improving bioenergetics, it is possible to treat almost any disease. A strong body will cope with all the sores. The state of overtraining can also be cured with energizers alone, incl. and carnitine. After all, the main reason for overtraining (and overwork) is the drop in the energy potential of the nerve centers that provide movement. A remarkable property of carnitine is its ability to reduce the content of cholesterol in the body and slow down the formation of atherosclerotic plaques in the vessels. Under the influence of carnitine, the formation of lecithin in the liver is enhanced. And here it does not do without highly mobile methyl radicals, which are necessary for the synthesis of lecithin in the liver. Lecithin is a substance that “washes out” cholesterol from atherosclerotic plaques. Carnitine is thus one of the few compounds whose use allows active longevity to be achieved.
Excess fat is something we all dream of getting rid of. Agree, cellulite does not paint women at all, and beer belly - men. But what do we know about fat?
Physiologists consider adipose tissue the most unusual part of the body and discover more and more new facts about it. First of all, fat accumulates reserves of nutrients that our body can use during times of hunger. Its other function is the release of hormones that control metabolism. In addition, as it turned out, in the human body there are different types fat.
Types of fat in human body
Brown (or brown) fat
The main function of brown fat is to generate heat. This is the same fatty layer that warms us in winter. Studies have found that slender people have more of this type of fat than those who tend to be overweight. Especially a lot of brown fat in children; it helps keep them warm. Fat of this type is present in the body in much smaller quantities than white fat - there are 100-200 other fat cells per cell of brown fat. Women have 5 times more brown fat cells than men. With age, the amount of brown fat decreases.
white fat
If the main function of brown fat is burning lipids and generating heat, then the function of white fat is cumulative. In the body, it is present in much larger quantities than brown fat. White fat cells produce the hormone adiponectin, which increases the sensitivity of the liver and muscles to the hormone insulin and makes us less prone to diabetes and heart disease.
When we are recruiting excess weight, the production of adiponectin slows down or stops, which increases our risk of these diseases.
In addition, fat in our body has different properties depending on where it is located.
subcutaneous fat
Subcutaneous fat on our thighs and buttocks poses almost no threat compared to the deeper type of fat, visceral fat. However, its excess deposits on the abdomen are also dangerous. Good news: this fat is easy to lose with proper nutrition, training, especially aerobic.
Visceral fat
Visceral fat is the "deep" fat that is deposited around the internal organs and extremely harmful to health. How to understand that you have it? If you have wide waist and belly then you have and visceral fat. This fat puts us at risk for diabetes, heart disease, stroke, or even dementia.
Visceral fat plays a larger role in insulin resistance, which increases the risk of diabetes, than any other type of fat. Doctors cannot yet explain why visceral fat is such a danger, but, nevertheless, it is so. Studies have also found that people with a lot of belly fat are more likely to develop dementia. There is a hypothesis that the hormone leptin, which secretes abdominal fat, can negatively affect the brain. Leptin regulates appetite as well as learning and memory. The good news is that visceral fat is easily eliminated by diet and exercise.
Gender related fat
Adipose tissue of this type is about 15% in the body in women and only 3% in men. In the female body, it is localized in the chest, buttocks and hips. Its quantity is determined by the individual constitution of the body. Getting rid of such fat is not easy, even with the help of loads and training. Having this type of adipose tissue can even be an advantage, especially for women. However, with age, this advantage disappears, and after menopause, women become prone to abdominal obesity.
abdominal fat
Excess belly fat has a justifiably bad reputation. It consists of both subcutaneous deposits and visceral adipose tissue. This fat is the most dangerous, since even in a calm state it is released into the liver, which converts it into “bad” cholesterol, which is extremely harmful to blood vessels. An excess of such fat increases the risk of cardiovascular disease and type 2 diabetes, metabolic syndrome, and high blood pressure.
The recipe for getting rid of this type of fat is still the same - diet and exercise. Especially useful aerobic training. Physical activity neutralizes most of the negative consequences abdominal obesity, and help get rid of the metabolic syndrome.
The group of lipids - important organic components of plant and animal cells - in addition to waxes and steroids, also includes fats. They are not only the most common, but also the most significant suppliers of energy for all the vital functions of the body: the synthesis of plastic substances, growth, and reproduction. what components it consists of, what properties and functions are characteristic of it - you will receive answers to these and many other questions in our article.
Features of physical properties
The ability to dissolve in organic solvents and antagonistic attitude towards water is the hallmark of lipids. All of them are lighter than water and oily to the touch. Leather, paper and other fibrous or porous materials quickly absorb excess. It is known from experience that stains of grease on clothes can be removed with gasoline, carbon tetrachloride, acetone or carbon disulfide. Esters of higher carboxylic acids and glycerol alcohol can have two states of aggregation: liquid or solid. Both vegetable and animal fats, the properties and use of which we are studying, are esters, the structural formula of which is determined by which carboxylic acids are included in their composition.
organic acids
This is a large group of substances containing carboxyl groups linked by covalent bonds to hydrocarbon radicals. If they have pi-bond molecules in the carbon skeleton, that is, they are unsaturated, then the compound will be liquid. For example, olive, linseed or sunflower oil contain oleic and linolenic acids with unsaturated chemical bonds. An exception here would be coconut oil, which belongs to vegetable lipids, but it is not liquid, but solid. Edible animal fats have a solid consistency. This is pork or as well as butter and various varieties of spread. They contain in their composition saturated carboxylic acids - stearic and palmitic. Interestingly, natural lipids are not separate connection, and a mixture of various glycerides - esters of glycerol and high molecular weight carboxylic acids.
The structure of the molecule
For a person who is far from the theoretical foundations of chemistry and not familiar with the provisions of the teachings of A. M. Butlerov, the structural formula of even the simplest lipid will seem cumbersome and obscure. In order not to complicate the topic, let's say the following: the obligatory presence in the molecule of trihydric alcohol glycerol and organic acid residues with at least 15 carbon atoms in the carbon skeleton is what vegetable or animal fat consists of. It doesn't matter if the lipid is natural or synthetic. The main thing is that all of them, without exception, belong to the class of esters and are formed as a result of the esterification reaction. Another interesting detail.
Up to early XIX century in science there was an opinion that organic substances: proteins, carbohydrates and lipids - can only be obtained from living organisms. The French chemist M. Berthelot in 1854 synthesized fat in his laboratory from glycerol and fatty acids. By this he refuted the erroneous ideas about the special exclusivity of organic compounds and the impossibility of obtaining them artificially.
esterification reaction
What is industrial fat made of? Its composition depends on which carboxylic acids have reacted with glycerol. Recall that if a triglyceride contains unsaturated acids, then it will be liquid, i.e., oil, and saturated carboxylic acids are included in the solid types of lipids. The esterification process is carried out in the presence of strong inorganic acids - sulfuric or chloride, the resulting products are quickly removed from the reaction sphere in order to prevent the hydrolysis of the resulting fat. The initial reagents themselves are always taken in excess, which also increases its practical yield.
Types and functions of fats
So, the main aggregate states of these compounds are liquid or solid phases. Oils contain unsaturated carboxylic acids with one or more double bonds. For example, oleic acid has one pi bond and is monounsaturated, found in olive or rapeseed oil, and found in peanuts, avocados, and olives. Fish fat, mussels, walnuts, as well as sunflower oil are rich in polyunsaturated acids: arachidonic, linoleic and linolenic. The biological functions of fats are not as diverse as, for example, proteins, but they are all vital. These are: protection, energy supply, excretory and thermal insulation properties. They are inherent in all substances of this class and do not depend on what fat consists of, or on what organism it is located in. The lipids secreted by the sebaceous glands lubricate the skin and protect it from dryness. They do not allow excess water to penetrate into the skin, which provides protection against edema. Substances that make up the fat body of insects, for example various kinds beetles, accumulate toxic metabolic products, thereby performing an excretory function.
The nutritional value
Lipids can also be distinguished according to such a criterion as the speed of cleavage and the qualitative composition of the hydrolyzate. This indicator must be taken into account when compiling various kinds of diets, in baby food, in the organization of the diet of people suffering from chronic cardiovascular diseases and diseases of the gastrointestinal tract. What are for the body? It is known that a diet rich in lipids containing omega-3 and omega-6 fatty acids helps maintain normal cholesterol levels and has a beneficial effect on vascular permeability. To do this, human food must contain linseed and olive oil, fish oil.
Excess in food solid types of lipids: lard, butter and margarine, leads to the formation of cholesterol plaques on the walls of the arteries, which impede blood circulation and provoke the formation of blood clots in them. This inevitably leads to an increased risk of coronary heart disease, often ending in a heart attack. To avoid such problems, fat intake should be subject to next rule: in the diet of a person who is responsible for his health, the presence of products containing
Hydrogenation: what is it?
Since we mentioned margarine, now is the time to find out how it is obtained. This is a solid artificially synthesized fat, the raw material for which are inexpensive varieties of edible vegetable oils. In order to convert them into a solid state, a chemical reaction is carried out, saturating the oils with hydrogen, the atoms of which are attached at the points of breaking double bonds in the remains of unsaturated acids. The process requires high pressure, heat, and powdered nickel as a catalyst. The resulting hydrogenation product, a hard fat, is called lard and is used as a raw material in the production of glycerin, soap or stearin.
What is the fat called margarine made of? This is a food product containing, in addition to lard, animal lipids, milk, salt, sugar, vitamins, food colors and flavors. Such fat is often called light butter or spread, it is much cheaper than butter and less caloric, which allows it to be used in dietary nutrition.
Hydrolysis - the main chemical property
We have previously established that fats are composed of glycerol and fatty acids, which are the initial reactants in the esterification reaction. In the presence of water and under the action of digestive enzymes in various parts of the gastrointestinal tract, they are split, which is accompanied by the release of the largest amount of energy compared to other organic compounds - proteins and carbohydrates. From one gram of fat, with its complete oxidation, 38.9 kJ of energy can be obtained. This is twice as much as in the hydrolysis of glucose. Therefore, to the question of what fat is, the answer may be the following statement: it is the most important organic substance that provides cells with the energy necessary for their life. Moreover, the breakdown of lipids is accompanied by the release a large number H 2 O molecules.
Lipids as a hidden reservoir of water
Adapting to various abiotic conditions, living beings strive to provide themselves with the compounds necessary for their life activity, leading role among which water plays. These are the inhabitants of the steppes and deserts: camels, jerboas, ground squirrels, field mice, etc. In addition, animals that tolerate winter or summer hibernation: Brown bear, sandy gopher, many species of shrews and insects, also receive the necessary water as a result of the breakdown of reserves in the subcutaneous tissue or fat body. There are some species of insects, for example, which do not need external sources of water at all, but extract it from the reactions of dissimilation of organic substances.
Lipids as a building material of cells
The most important components of living systems are biological membranes. Due to the liquid-mosaic structure, they have unique functions: signal and protective properties. The composition of all cell membranes includes lipids, about 30% of which are connected to protein globules, and the rest are in the liquid phase. We remember what substances fats consist of - these are glycerol and organic acid residues, the molecules of which are arranged in the form of a double layer. Hydrophilic components are oriented towards the outer and internal parts membrane, and water-insoluble areas are turned into its middle. Most cell organelles, such as the nucleus, chloroplasts, mitochondria, Golgi apparatus, endoplasmic reticulum, and lysosomes, have a membrane structure. All of them contain fat molecules, which are the building blocks of the cell.
Protective properties
Fats in the body of humans and other mammals are part of They can serve as armor that reliably covers vital organs, such as the kidneys, from mechanical shocks during movement, as well as from blows and injuries. If the living conditions of the organism are extreme, for example, it stays in ice water for a long time, then fat reserves save it from hypothermia. In seals, walruses and fur seals, the lipid layer can be 15-20 cm, and in the largest animal in the world - the blue whale, it exceeds half a meter in thickness! Therefore, the question of what fat is can be answered this way: it is the main heat-insulating material of homoiothermic organisms, that is, those who maintain a constant body temperature.
What happens to fats in our body?
Products rich in lipids are partially broken down in the stomach under the action of enzymes secreted by its mucous membrane. But their main hydrolysis occurs in the duodenum under the action of lipase, which is part of the pancreatic juice. An important role belongs to the bile produced by the liver. It, like a crusher, breaks lipid macromolecules into smaller parts - emulsifies them. This promotes a better and faster hydrolysis process leading to the formation of glycerol and fatty acids. The hydrolyzate is absorbed by the villi of the small intestine, first into blindly closed capillaries. lymphatic system, and from them enters the blood. From glycerol and carboxylic acids, cells synthesize fats specific to a given organism, some of which can be deposited in the subcutaneous adipose tissue and the omentum - a kind of fat depot. During periods of prolonged fasting, with severe physical activity or stress, the body uses these reserves to get energy.
lipid and carbohydrate metabolism
Both groups of organic compounds: sugars and fats, cells can use as energy material. Excess glucose is converted by hepatocytes into the form of a polymer - animal starch glycogen. Products of lipid hydrolysis also enter the liver, where they are converted into the same glycogen. Excess carbohydrates in gastrointestinal tract with improper nutrition, in turn, it is transformed into fat, and a person quickly gains weight. These facts serve as evidence of the relationship between fat and carbohydrate metabolism, confirming important role lipids in our body.
We eat fats from birth, our body produces lipases - enzymes necessary for the digestion of food fats. Fats cannot be used by us until they are broken down by lipase to their constituent elements. After the intake of fats in the body, they cannot immediately be deposited in the tissues, so the consumption of a large amount of monounsaturated fatty acids does not mean that they will go into our own fat depots and somehow change their composition. The composition of human fat is fairly constant and looks like this: 49% oleic acid; 27% palmitic acid; 9% linoleic acid; 8% palmitoleic acid and 7% stearic acid. Thus, our body contains 34% saturated (palmitic, stearic) and 66% unsaturated (oleic, linoleic, palmitoleic) fatty acids, and among the unsaturated 57% are monounsaturated (oleic, palmitic) and 9% are polyunsaturated (linoleic). ) fatty acid. 9% of polyunsaturated fatty acids are exclusively omega-6 fatty acids Omega-3 fatty acids are almost not stored in the human body.
At the very beginning of life, we cannot control the intake of fatty acids into our body, nature does this for us. The breast of a nursing woman produces milk, which is food for her baby. A liter of milk contains 750 kilocalories of energy, such energy intensity is sufficient for a baby. The composition of milk changes during the first two weeks after childbirth, the content in it is halved (from 23 grams per liter to 11 grams), at the same time the content increases (from 57 grams of lactose per liter to 70 grams), the same happens with fats (the content increases from 30 grams per liter to 45 grams). The percentage of fat in milk increases during each feeding of the child, their content can vary from 10 grams per liter at the beginning of feeding to 60 grams at the end. That part of it, which is produced in the anterior part of the mammary gland, is called "front" milk, it has less fat, but more lactose, the child drinks first. "Hinder" milk, formed by the cells of the deeper parts of the gland, it has more fat, and it is drunk by the child last.
Human milk contains 50% saturated and 50% unsaturated fatty acids. Unsaturated fatty acids in milk include: palmitic (26%), stearic (8%), myristic (8%), lauric (5%) and arachidonic (1%) acids, as well as some others contained in milk in small quantities. Monounsaturated acids of milk are oleic (35%) and palmitoleic (3%); polyunsaturated acid of milk - omega-6 linoleic acid (10%), other polyunsaturated acids are found in milk in small quantities. The omega-3 fatty acids of milk are linolenic and arachidonic, the content of which is 0.9% and 0.6%, respectively.
