Chemically, most lipids are esters of higher carboxylic acids and a number of alcohols. The most famous among them are fats. Each fat molecule is formed by a molecule of the triatomic alcohol glycerol and the ester bonds of three molecules of higher carboxylic acids attached to it. According to the accepted nomenclature, fats are called triacyl glycerols.
Carbon atoms in molecules of higher carboxylic acids can be connected to each other by both simple and double bonds. Of the saturated (saturated) higher carboxylic acids, palmitic, stearic, and arachidic acids are most often found in fats; from unsaturated (unsaturated) - oleic and linoleic.
The degree of unsaturation and chain length of higher carboxylic acids (i.e., the number of carbon atoms) determine physical properties one kind of fat or another.
Fats with short and unsaturated acid chains have a low melting point. At room temperature These are liquids (oils) or ointment-like substances (fats). Conversely, fats with long and saturated chains of higher carboxylic acids become solid at room temperature. This is why, when hydrogenation occurs (the saturation of acid chains with hydrogen atoms at double bonds), liquid peanut butter, for example, becomes creamy and sunflower oil turns into hard margarine. Compared to the inhabitants of southern latitudes, in the body of animals living in cold climates (for example, in fish arctic seas), usually contains more unsaturated triacylglycerols. For this reason, their body remains flexible even when low temperatures.
In phospholipids, one of the extreme chains of higher carboxylic acids of triacylglycerol is replaced by a group containing phosphate. Phospholipids have polar heads and nonpolar tails. The groups forming the polar head group are hydrophilic, while the non-polar tail groups are hydrophobic. The dual nature of these lipids determines their key role in the organization of biological membranes.
Another group of lipids consists of steroids (sterols). These substances are based on cholesterol alcohol. Sterols are poorly soluble in water and do not contain higher carboxylic acids. These include bile acids, cholesterol, sex hormones, vitamin D, etc.
Lipids also include terpenes (plant growth substances - gibberellins; carotenoids - photosynthetic pigments; essential oils plants, as well as wax).
Lipids can form complexes with other biological molecules - proteins and sugars.
The functions of lipids are as follows:
Structural. Phospholipids together with proteins form biological membranes. The membranes also contain sterols.
Energy. When fats are oxidized, a large amount of energy is released, which goes towards the formation of ATP. A significant portion of the body’s energy reserves are stored in the form of lipids, which are consumed when there is a lack of nutrients. Hibernating animals and plants accumulate fats and oils and use them to maintain vital processes. The high lipid content in plant seeds ensures the development of the embryo and seedling before they transition to independent nutrition. The seeds of many plants (coconut palm, castor oil, sunflower, soybean, rapeseed, etc.) serve as raw materials for producing vegetable oil industrially.
Protective and thermal insulating. Accumulating in subcutaneous tissue and around some organs (kidneys, intestines), the fat layer protects the animal’s body and its individual organs from mechanical damage. In addition, due to low thermal conductivity, the layer of subcutaneous fat helps retain heat, which allows, for example, many animals to live in cold climates. In whales, in addition, it plays another role - it promotes buoyancy.
Lubricating and water repellent. Wax covers the skin, wool, feathers, makes them more elastic and protects them from moisture. The leaves and fruits of many plants have a waxy coating.
Regulatory. Many hormones are derivatives of cholesterol, such as sex hormones (testosterone in men and progesterone in women) and corticosteroids (aldosterone). Cholesterol derivatives, vitamin D play a key role in the metabolism of calcium and phosphorus. Bile acids are involved in the processes of digestion (emulsification of fats) and absorption of higher carboxylic acids.
Lipids are also a source of metabolic water. Oxidation of 100 g of fat produces approximately 105 g of water. This water is very important for some desert inhabitants, in particular for camels, which can do without water for 10-12 days: the fat stored in the hump is used precisely for these purposes. Bears, marmots and other hibernating animals obtain the water they need for life as a result of fat oxidation.
In the myelin sheaths of axons nerve cells Lipids are insulators during the conduction of nerve impulses.
Wax is used by bees to build honeycombs.
The main rule for maintaining health is to evenly distribute the proportion of fat when serving a dish. In fact, a person needs fats, but he must control the amount of fat consumed. A person must determine for himself the amount of fat that will be beneficial and not harmful to health. Fat must go into the right direction, to avoid unpleasant consequences associated with weight gain, which leads to heart problems, hypertension, stroke or even death. Therefore, it is worth paying attention to foods that help burn fat. Today we will look at 10 unknown facts about fats.
On average, an average person purchases 1 g every day excess fat
. In reality, people gain more body fat. More attention should be paid to nutrition and physical activity. Draw conclusions: The higher your fat intake, the sooner health problems will begin.
Fat cells live for ten years after a person's death. However, they die under the influence physical activity. The problem is that brain cells are constantly dying and being renewed, but if their place is taken fat cells, memory problems occur, especially in older people.
8. Source of calories
In fact, fat is an essential source of calories. necessary for the body. It is vital for maintaining all vital processes in the body. It is worth remembering that excess weight leads to health problems. The main rule is choice the right products with enough calories for the body to function.
7. Fat enhances flavor
Most preservatives and flavor enhancers are based on fat. When you mix them with food, it acquires a pleasant and alluring aroma and taste. If you like to cook, try adding meat or animal fat to the dish; the smell and taste will immediately change.
Fat is a kind of absorbent for vitamins. People who regularly take vitamins notice that after eating, the effect of the vitamins is felt weaker. Especially if the vitamins are in soluble form.
5. Women need fat more than men.
First of all, women's greater need for fat is associated with nature. A woman is a mother, in order to conceive a child, the body requires strength to bear the child and grow it in the womb, the body burns calories and fats, and finally, after the birth of the child, the woman breastfeeds, and the basis of milk is lactose and fat. The fat reserves in a woman's body are explained by the fact that the body saves energy for the expectant mother. This is why many women lose weight after breastfeeding.
There are two types of fat. They are figuratively called good and bad. Good fat refer to unsaturated fats, such fats are necessary to the human body. They are found in lean white meat and steamed foods, such as fish. Bad fats are fatty meats, chicken skin or dairy products. Consumption of these foods leads to high cholesterol and heart problems.
Since fat contains high levels of calories, they are stored as energy.. Consuming 1 gram of fat equals 9 calories.
2. Fat storage
The fat needed for health is stored in the muscles, bone marrow and organs nervous system. It is simply necessary for the production of hormones and increased immunity. Subcutaneous fat is an indicator that it is time to lose weight. Fat is found in foods that increase muscle mass.
Women should maintain between 13 and 17% body fat, which are usually stored in the hips, chest, thighs and abdomen. In men, fat is stored in the abdomen. They should maintain a body fat percentage of 3 to 5%, which is significantly less than for women.
Lipids (Fats).Lipids- called a complex mixture organic compounds(compounds with carbon C), with similar physicochemical properties:
- insoluble in water.
- good solubility in organic solvents (gasoline, chloroform)Lipids are widely distributed in nature. Together with proteins and carbohydrates, they make up the bulk of the organic substances of all living organisms, being an essential component of every cell. Lipids are the most important component of food, largely determining its nutritional value and taste.
In plants they accumulate mainly in seeds and fruits. In animals and fish, lipids are concentrated in subcutaneous adipose tissues, in abdominal cavity and tissues surrounding many important organs(heart, kidneys), as well as in brain and nervous tissues. There are especially many lipids in the subcutaneous adipose tissue of whales (25-30% of their mass), seals and other marine animals. In humans, lipid content ranges from 10-20% on average.Types of lipids.
There are many types of classifications of fats, we will analyze the simplest one, it divides them into three large groups:
- Simple lipids
- Complex lipids
- Lipid derivatives.Let's look at each group of lipids separately, what they contain, and what they are needed for.
Simple Lipids.
1) Neutral fats (or just fats).
Neutral fats consist of triglycerides.
Triglyceride - a lipid or neutral fat that contains glycerol combined with three molecules of fatty acids.
Glycerol- chemical compound with the formula C3H5(OH)3, (colorless, viscous, odorless, sweetish liquid.)
Fatty acid– natural or created compounds with one or more groups - COOH (carboxyl) that do not create cyclic bonds (aromatic), with the number of carbon atoms (C) in the chain of at least 6.Triglycerides are produced from the breakdown of dietary fats and are a form of fat storage in the human body. The bulk of dietary fats (98%) are triglycerides. Fat is also stored in the body in the form of triglycerides.
Types of fatty acids:
- Saturated fatty acids- contain only single bonds between carbon atoms with all other bonds attached to hydrogen atoms. The molecule combines with as many hydrogen atoms as possible, which is why the acid is called saturated. They differ from unsaturated acids in that they remain solid at room temperature.
Foods that contain the most saturated fat are lard and fat, chicken, beef and lamb fat, butter and margarine. Foods rich in such fats include sausage, sausages and other sausages, bacon, regular lean beef; varieties of meat called “marbled”; chicken skin, bacon; ice cream, creams, cheeses; most of the flour and other confectionery products.- unsaturated fatty acids - contain one or more double bonds along the main carbon chain. Each double bond reduces the number of hydrogen atoms that can bond with the fatty acid. Double bonds also result in a "bend" in the fatty acids, which prevents bonding between them.
Unsaturated fatty acids are found in plant sources.They can be divided into two types:
1) monounsaturated – unsaturated fatty acids with one double bond. (for example - olive oil)
2) polyunsaturated - unsaturated fatty acids with two or more double bonds. (for example - linseed oil)There will be a separate large topic about dietary fats, examining in detail all their properties.
2) Waxes.
Waxes are fat-like substances of animal or plant origin, consisting of esters of monohydric alcohols and fatty acids.
Esters– compounds – COOH (carboxyl) in which the hydrogen atom in the HO group is replaced by an organic group.
Alcohols– –OH compounds bonded to a carbon atom.
In simple words, waxes are shapeless, plastic substances that soften easily when heated, melting in the temperature range from 40 to 90 degrees Celsius.
Beeswax is secreted by special glands of honey bees, from which bees build honeycombs.Complex lipids.
A complex lipid is a combination of a triglyceride with other chemicals.
There are three types in total.Phospholipids– glycerol combined with one or two fatty acids as well as phosphoric acid.
The cell membrane is made up of phospholipids. The most popular in food products is lecithin.Glycolipids – compounds of fatty and carbohydrate components. (Contained in all tissues, mainly in the outer lipid layer of plasma membranes.)
Lipoproteins– complexes of fats and proteins. (Blood plasma)
Lipid derivatives.
Cholesterol- a fatty, wax-like substance found in every cell of the body and in many foods. Some cholesterol in the blood is necessary, but high levels can lead to heart disease.
A lot of cholesterol is found in eggs, fatty meats, sausages, and fatty dairy products.WITH general classification Have you figured out what functions lipids perform?
Functions.
- Structural function.
Phospholipids take part in the construction of cell membranes of all organs and tissues. They are involved in the formation of many biologically important compounds.
- Energy function.
When fats are oxidized, a large amount of energy is released, which goes towards the formation of ATP. A significant portion of the body's energy reserves are stored in the form of lipids, which are consumed when there is a lack of nutrients. Hibernating animals and plants accumulate fats and oils and use them to maintain vital processes. The high lipid content in plant seeds ensures the development of the embryo and seedling before they transition to independent nutrition. The seeds of many plants (coconut palm, castor oil, sunflower, soybean, rapeseed, etc.) serve as raw materials for the production of vegetable oil industrially. With the complete breakdown of 1 g of fat, 38.9 kJ of energy is released, which is approximately 2 times more compared to carbohydrates and proteins.
- Protective and thermal insulation
Accumulating in the subcutaneous tissue and around some organs (kidneys, intestines), the fat layer protects the animal’s body and its individual organs from mechanical damage. In addition, due to low thermal conductivity, the layer of subcutaneous fat helps retain heat, which allows, for example, many animals to live in cold climates.
Lubricating and water repellent.
Wax covers the skin, wool, feathers, makes them more elastic and protects them from moisture. The leaves and fruits of many plants have a waxy coating.- Regulatory.
Many hormones are derivatives of cholesterol, for example sex hormones (testosterone at men and progesterone in women) and corticosteroids. Cholesterol derivatives, vitamin D play a key role in the metabolism of calcium and phosphorus. Bile acids are involved in digestion processes. In the myelin (non-conductive charge) sheaths of the axons of nerve cells, lipids are insulators during the conduction of nerve impulses.
- Source of metabolic water.
Oxidation of 100 g of fat produces approximately 105-107 g of water. This water is very important for some desert inhabitants, in particular for camels, which can do without water for 10-12 days: the fat stored in the hump is used precisely for these purposes. Bears, marmots and other hibernating animals obtain the water they need for life as a result of fat oxidation.
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Lipids in nutrition
Along with proteins and carbohydrates, lipids are the main nutritional elements that make up a significant part of food. The intake of lipids into the body from food has a significant impact on human health in general. Insufficient or excessive consumption of these substances can lead to the development of various pathologies. Most people eat a fairly varied diet, and their bodies get everything essential lipids. It should be noted that some of these substances are synthesized by the liver, which partly compensates for their lack in food. However, there are also essential lipids, or rather their components - polyunsaturated fatty acids. 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 used by the body to produce energy. This is why when fasting a person loses weight and becomes weaker. Deprived of energy, the body begins to consume lipid reserves from subcutaneous fat.
Thus, lipids play a very important role in healthy eating person. However, for some diseases or disorders, their quantity should be strictly limited. Patients usually learn about this from their attending physician ( usually a gastroenterologist or nutritionist).
Energy value of lipids and their role in diet
The energy value of any food is calculated in calories. A food product can be broken down according to its composition into proteins, carbohydrates and lipids, which together make up the bulk. Each of these substances breaks down in the body, releasing a certain amount of energy. Proteins and carbohydrates are digested more easily, but the breakdown of 1 g of these substances releases about 4 Kcal ( kilocalories) energy. Fats are more difficult to digest, but the breakdown of 1 g releases about 9 kcal. Thus, energy value lipids is the highest.In terms of energy release, triglycerides play the largest role. Saturated acids, included in these substances, are absorbed by the body by 30–40%. Monounsaturated and polyunsaturated fatty acids are completely absorbed by a healthy body. Adequate lipid intake allows carbohydrates and proteins to be used for other purposes.
Plant and animal lipids
All lipids entering the body with food can be divided into substances of animal and plant origin. From a chemical point of view, the lipids that make up these two groups differ in their composition and structure. This is explained by differences in the functioning of cells in plants and animals.Examples of plant and animal lipid sources
Each lipid source has certain advantages and disadvantages. For example, animal fats contain cholesterol, which is not found in plant foods. In addition, animal products contain more lipids and are more energy efficient to consume. At the same time, excess animal fat increases the risk of developing a number of diseases associated with lipid metabolism in the body ( atherosclerosis, cholelithiasis, etc.). Plant foods contain fewer lipids, but the body cannot synthesize them on its own. Even a small amount of seafood, citrus fruits or nuts supplies enough polyunsaturated fatty acids, which are vital for humans. At the same time, a small proportion of lipids in plants cannot fully cover the body’s energy costs. That is why, to maintain health, it is recommended to make your diet as varied as possible.
What is the body's daily requirement for lipids?
Lipids are the main suppliers of energy to the body, but their excess can be harmful to health. First of all, this concerns saturated fatty acids, most of which are deposited in the body and often lead to obesity. The optimal solution is to maintain the required proportions between proteins, fats and carbohydrates. The body must receive the same number of calories that it expends during the day. This is why lipid intake rates may vary.The body's need for lipids can be influenced by the following factors:
- Body weight. Overweight people have to expend more energy. If they are not going to lose weight, then the need for calories and, accordingly, lipids will be slightly higher. If they want to lose weight, then, first of all, they need to limit fatty foods.
- Loads during the day. People who do heavy physical work or athletes need a lot of energy. If the average person has 1500 - 2500 calories, then for miners or loaders the norm can reach 4500 - 5000 calories per day. Of course, the need for lipids also increases.
- Nature of nutrition. Every country and every people has its own food traditions. When calculating the optimal diet, you need to take into account exactly what foods a person usually consumes. For some peoples, fatty foods are a kind of tradition, while others, on the contrary, are vegetarians, and their lipid intake is kept to a minimum.
- 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 gall bladder, since these organs are responsible for the digestion and absorption of lipids.
- The age of the person. IN childhood 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 digest any food well. It should also be taken into account that infants receive an optimal set of lipids through breast milk. Thus, age greatly influences the rate of fat intake.
- Floor. It is believed that on average a man consumes more energy than a woman, so the norm of fat in men's diet is slightly higher. However, in pregnant women, the need for lipids increases.
It is difficult for a person to make the necessary calculations on his own and take into account all the factors to select the optimal diet. To do this, it is better to consult a nutritionist or food hygiene specialist. After a short survey and clarification of the nature of nutrition, they will be able to create an optimal daily diet that the patient will adhere to in the future. They can also recommend specific foods that contain essential lipids.
Which foods mainly contain lipids ( milk, meat, etc.)?
Almost all food products contain lipids in varying quantities. However, in general, animal products are richer in these substances. In plants mass fraction lipids is minimal, but the fatty acids included in such lipids are the most important for the body.The amount of lipids in a particular product is usually indicated on the product packaging in the section “ the nutritional value" Most manufacturers are required 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 indicate all the main products and dishes.
Mass fraction of lipids in staple foods
In most products of plant origin ( vegetables, fruits, herbs, root vegetables) the mass fraction of fats is no more than 1 – 2%. The exceptions are citrus fruits, where the proportion of lipids is slightly higher, and vegetable oils, which are a concentrate of lipids.
Are there essential lipids, and what are their most important sources?
The structural unit of lipids is fatty acids. Most of these acids can be synthesized by the body ( mainly by liver cells) from other substances. However, there are a number of fatty acids that the body cannot produce on its own. Thus, lipids containing these acids are essential.Most of essential lipids found in foods of plant origin. These are monounsaturated and polyunsaturated fatty acids. Body cells cannot synthesize these compounds, since the metabolism of animals is very different from that of plants.
Essential fatty acids and their main dietary sources
For a long time, the above fatty acids were equated in importance to vitamins for the body. Sufficient consumption of these substances strengthens the immune system, accelerates cell regeneration, and reduces inflammatory processes, promotes the conduction of nerve impulses.
What does a lack or excess of lipids in the diet lead to?
Both deficiency and excess of lipids in the diet can seriously affect the health of the body. IN in this case It's not a one-time thing large quantity fat ( although this may cause certain consequences), but about the systematic abuse of fatty foods or prolonged fasting. At first, the body is quite capable of successfully adapting to a new diet. For example, if there is a lack of lipids in food, the most important substances for the body will still be synthesized by the body’s own cells, and energy needs will be covered by the breakdown of fat reserves. If there is an excess of lipids in the diet, a significant part will not be absorbed in the intestine and will leave the body with fecal matter, and some of the lipids that enter the blood will be transformed into adipose tissue. However, these adaptation mechanisms are temporary. In addition, they work well only in a healthy body.Possible consequences of lipid imbalance in the diet
Blood and plasma lipids
A significant portion of lipids are present in the blood in various forms. Most often these are compounds of lipids with other chemicals. For example, triglycerides and cholesterol are transported primarily as lipoproteins. The levels of various lipids in the blood can be determined using biochemical blood tests. This makes it possible to identify a number of disorders and suspect corresponding pathologies. Triglycerides
Triglycerides perform mainly energy function. They enter the body with food, are absorbed in the intestines and are carried throughout the body through the blood in the form of various compounds. The normal level is considered to be 0.41 - 1.8 mmol/l, but it can fluctuate within significant limits. For example, after consuming a large amount fatty foods The level of triglycerides in the blood may increase 2–3 times.Free fatty acids
Free fatty acids enter the blood as a result of the breakdown of triglycerides. Normally, they are deposited in adipose tissue. Modern research showed a relationship between the level of free fatty acids in the blood and some pathological processes. For example, in people with high concentrations of fatty acids ( on an empty stomach) insulin is produced worse, so the risk of developing diabetes is higher. The normal content of fatty acids in the blood of an adult is 0.28 – 0.89 mmol/l. In children, the normal limits are wider ( up to 1.10 mmol/l).Cholesterol
Cholesterol is one of the most important lipids in the human body. It is part of many cellular components and other substances, influencing a variety of processes. An excess or deficiency of this substance or disruption of its absorption by the body can lead to the development of serious diseases.In the human body, cholesterol performs the following functions:
- imparts rigidity to cell membranes;
- takes part in the synthesis of steroid hormones;
- is part of bile;
- participates in the absorption of vitamin D;
- regulates the permeability of the walls of certain cells.
Lipoproteins ( lipoproteins) and their factions ( low density, high density, etc.)
The term lipoproteins or lipoproteins refers to a group of complex protein compounds that transport lipids in the blood. Some lipoproteins are fixed in cell membranes and perform a number of functions related to cell metabolism.All blood lipoproteins are divided into several classes, each of which has its own characteristics. The main criterion by which lipoproteins are distinguished is their density. According to this indicator, all these substances are divided into 5 groups.
There are the following classes ( factions) lipoproteins:
- High density. HDL) take part in the transfer of lipids from body tissues to the liver. From a medical point of view, they are considered useful because, due to their small size, they can pass through the walls of blood vessels and “cleanse” them of lipid deposits. Thus, high HDL levels reduce the risk of developing atherosclerosis.
- Low density. LDL) transport cholesterol and other lipids from the liver ( places of their synthesis) to tissues. From a medical point of view, this fraction of lipoproteins is harmful, since it is LDL that promotes the deposition of lipids on the walls of blood vessels with the formation of atherosclerotic plaques. High LDL levels greatly increase the risk of developing atherosclerosis.
- Average ( intermediate) density. Intermediate density lipoproteins ( BOB) do not have significant diagnostic value, since they are an intermediate product of lipid metabolism in the liver. They also transport lipids from the liver to other tissues.
- Very low density. VLDL) transport lipids from the liver to tissues. They also increase the risk of developing atherosclerosis, but play a minor role in this process ( after LDL).
- Chylomicrons. Chylomicrons are significantly larger than other lipoproteins. They form in the walls small intestine and transport lipids supplied with food to other organs and tissues. In the development of various pathological processes these substances do not play a significant role.
Lipid analysis
Currently there are many laboratory tests, with which you can determine various lipids in the blood. Usually this is done deoxygenated blood. The patient is sent for analysis by the attending physician. The most important lipids (total cholesterol, triglycerides) are determined in biochemical analysis blood. If the patient needs a more detailed examination, the doctor indicates which lipids need to be determined. The analysis itself usually lasts several hours. Most laboratories provide results the next day. What is a lipid profile?
A lipidogram is a set of laboratory blood tests aimed at determining the level of lipids in the blood. This is the most useful test for patients with various disorders lipid metabolism, as well as for patients with atherosclerosis. Some indicators included in the lipid profile are also determined in a biochemical blood test, but in some cases this may not be enough to diagnose accurate diagnosis. A lipidogram is prescribed by the attending physician, based on the patient’s symptoms and complaints. This analysis is carried out by almost any biochemical laboratory.The lipidogram includes tests to determine the following blood lipids:
- Cholesterol. This indicator does not always depend on lifestyle and nutrition. A significant part of the cholesterol in the blood is the so-called endogenous cholesterol, which is produced by the body itself.
- Triglycerides. Triglyceride levels usually rise or fall 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 developing atherosclerosis.
- Lipoproteins high density (HDL). These compounds are able to “clean” blood vessels from excess cholesterol and are beneficial for the body. Low level HDL indicates that the body does not absorb fat well.
- Very low density lipoproteins ( VLDL). They have a secondary diagnostic value, but their increase along with an increase in LDL levels usually indicates atherosclerosis.
Before donating blood for a lipid profile, you should follow several simple rules. They will help avoid significant fluctuations in blood lipid levels and make the results more reliable.
Before taking the test, patients should consider the following recommendations:
- You can eat in the evening before the test, but you should not overeat fatty foods. It is better to stick to your usual diet.
- The day before the test, it is necessary to exclude various types of loads ( both physical and emotional), as they can lead to the breakdown of fat reserves in the body and increase blood lipid levels.
- In the morning, immediately before donating blood, you should not smoke.
- Regular use of a number of drugs also affects the level of lipids in the blood ( contraceptive drugs, hormonal drugs and etc.). It is not necessary to cancel them, but this fact must be taken into account when interpreting the results.
Normal blood lipid levels
The limits of the norm are somewhat different for all people. It depends on gender, age, availability chronic pathologies and a number of other indicators. However, there are certain limits, exceeding which clearly indicates the presence of problems. The table below shows generally accepted normal limits for various blood lipids.The limits of the norm are relative, and the patient himself cannot always draw the right conclusions when interpreting the results of the analysis. When reviewing the results, the attending physician will definitely take into account that during pregnancy the normal limits expand, as well as during fasting. Therefore, there is no need to panic if there are some deviations from the norm. In any case, the final conclusion must be made by the attending physician.
Diseases associated with lipid metabolism
There are quite a few diseases that are, to one degree or another, related to lipid metabolism in the body. Some of these pathologies cause an increase or decrease in various lipids in the blood, which is reflected in the tests. Other pathologies are a consequence of lipid imbalance. Lipid metabolism disorders ( dyslipidemia)
Excess or lack of lipids in the diet can lead to a variety of pathologies. In a healthy body that normally absorbs all incoming substances, this imbalance does not affect metabolic processes as much. For example, excess lipids do not always lead to obesity. To do this, a person must also have genetic predisposition, endocrine disorders, or he must lead sedentary lifestyle life. In other words, the amount of lipids in the diet in most cases is only one of many factors influencing the occurrence of pathology.Lipid imbalance can lead to the following pathologies:
- atherosclerosis ( as a result - aneurysms, coronary heart disease, hypertension or other problems with the cardiovascular system);
- skin problems;
- problems with the nervous system;
- a number of pathologies gastrointestinal tract (pancreatitis, cholelithiasis, etc.).
Causes of high and low lipid levels
The most common cause of elevated lipid levels in a blood test is errors made during blood donation. Patients do not donate blood on an empty stomach, which is why lipid levels do not have time to normalize, and the doctor may mistakenly suspect some problems. However, there are many pathologies that cause disturbances in blood lipids, regardless of nutrition.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 level of triglycerides in the blood is elevated, they speak of hypertriglyceridemia ( synonym – hyperlipemia). If cholesterol levels increase, they speak of hypercholesterolemia.
Also, all dyslipidemias by origin are divided into the following groups:
- Primary. Primary dyslipidemias generally mean genetic diseases and deviations. As a rule, they are manifested by an excess or deficiency of any enzymes, which disrupts lipid metabolism. As a result, the amount of these substances in the blood decreases or increases.
- Secondary. Secondary dyslipidemia refers to pathological conditions in which an 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 lipid level will gradually stabilize.
There are five main types of primary hyperlipoproteinemia ( increased level lipoproteins):
- Hyperchylomicronemia. With this disease, the level of triglycerides in the blood increases, while the level of other lipids usually remains within normal limits. Patients may experience paroxysmal abdominal pain, but without tension in the abdominal muscles. Xanthomas may appear on the skin ( formation of brown or yellowish color ). The disease does not lead to the development of atherosclerosis.
- Familial hyper-beta lipoproteinemia. With this pathology, the amount of beta-lipoproteins, and sometimes pre-beta-lipoproteins, increases. The analysis showed significantly higher cholesterol levels. Triglyceride levels may be normal or slightly elevated. Patients also develop xanthomatosis ( xanthomas on the skin). The risk of atherosclerosis increases significantly. With this disease, myocardial infarction is possible even at a young age.
- Familial hypercholesterolemia with hyperlipemia. The levels of both cholesterol and triglycerides in the blood are significantly elevated. Xanthomas are large and appear after 20–25 years. Increased risk of developing atherosclerosis.
- Hyper-pre-beta lipoproteinemia. In this case, the level of triglycerides increases, and the level of cholesterol remains within normal limits. The disease is often combined with diabetes mellitus, gout or obesity.
There are also secondary ( symptomatic) hyperlipoproteinemia in the following diseases:
- Diabetes. In this case, the excess lipids in the blood are explained by the transformation of excess carbohydrates.
- Acute pancreatitis. With this disease, the absorption of lipids is disrupted, and their level in the blood increases due to the breakdown of adipose tissue.
- Hypothyroidism. The disease is caused by a lack of thyroid hormones, which also regulate lipid metabolism in the body.
- Intrahepatic cholestasis and other liver pathologies. The liver takes part in the synthesis of most of the lipids needed by the body. With various hepatitis, bile outflow disorders and other pathologies of the liver and bile ducts, the level of lipids in the blood may increase.
- Nephrotic syndrome. This syndrome develops when the glomerular apparatus of the kidneys is damaged. Patients experience severe renal edema. The level of proteins in the blood drops, 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 disrupted, as a result of which porphyrins accumulate in the blood. In parallel, lipid levels may increase ( sometimes significantly).
- Some autoimmune diseases. At autoimmune diseases Antibodies produced by the body attack its own cells. In most cases, chronic inflammatory processes develop, which are associated with increased lipid levels.
- Gout. With gout, the metabolism of uric acid in the body is disrupted, and it accumulates in the form of salts. This is partly reflected in lipid metabolism, although their level in this case is slightly increased.
- Alcohol abuse. Alcohol abuse leads to pathologies of the liver and gastrointestinal tract. A number of enzymes may be activated that increase blood lipid levels.
- Taking certain medications. Increased lipid levels can result from, for example, long-term use oral contraceptives ( contraception ). Most often about this side effect mentioned in the instructions for the corresponding drug. Before taking the test, you should not take such drugs, or you should warn the treating physician about this so that he can correctly interpret the test results.
Also, increased levels of lipoproteins in the blood can be observed during pregnancy. This increase is usually minor. When lipid levels increase 2 to 3 times higher than normal, the likelihood of pregnancy in combination with other pathologies must be considered, causing an increase lipid levels.
What diseases of the digestive system are associated with lipid metabolism?
healthy digestive system is collateral good absorption lipids and other nutrients. A significant imbalance of lipids in food over a long period of time can lead to the development of certain gastric pathologies. One of the most common problems in cardiology is atherosclerosis. This disease occurs due to the deposition of lipids in blood vessels ( mainly in arteries). As a result of this process, the lumen of the vessel narrows and blood flow becomes difficult. Depending on which arteries are affected by atherosclerotic plaques, patients may experience various symptoms. The most common type is high blood pressure, ischemic disease hearts ( sometimes myocardial infarction), the appearance of aneurysms.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 arbitrary. In addition to the chemical nature of substances, the development of this disease Many other factors also contribute.
Atherogenic lipids more often lead to the development of atherosclerosis in the following cases:
- heavy smoking;
- heredity;
- diabetes;
- overweight ( obesity);
- sedentary lifestyle ( physical inactivity) and etc.
What are lipids, what is the classification of lipids, what is their structure and function? The answer to this and many other questions is given by biochemistry, which studies these and other substances that have great importance for metabolism.
What it is
Lipids are organic matter, insoluble in water. The functions of lipids in the human body are diverse.
Lipids - this word means "small particles of fat"
This is first of all:
- Energy. Lipids serve as a substrate for storing and using energy. When 1 gram of fat is broken down, approximately 2 times more energy is released than when protein or carbohydrates of the same weight are broken down.
- Structural function. The structure of lipids determines the structure of the membranes of the cells of our body. They are arranged in such a way that the hydrophilic part of the molecule is located inside the cell, and the hydrophobic part is on its surface. Thanks to these properties of lipids, each cell, on the one hand, is autonomous system, fenced off from the outside world, and on the other hand, each cell can exchange molecules with others and with environment using special transport systems.
- Protective. The surface layer that we have on our skin and serves as a kind of barrier between us and the outside world is also made up of lipids. In addition, they, as part of adipose tissue, provide thermal insulation and protection from harmful external influences.
- Regulatory. They are part of vitamins, hormones and other substances that regulate many processes in the body.
The general characteristics of lipids are based on their structural features. They have dual properties, since they have a soluble and insoluble part in the molecule.
Entry into the body
Lipids partly enter the human body with food, and partly can be synthesized endogenously. Splitting the main part dietary lipids occurs in the duodenum under the influence of pancreatic juice secreted by the pancreas and bile acids as part of bile. Having broken down, they are resynthesized again in the intestinal wall and, already as part of special transport particles ─ lipoproteins, ─ are ready to enter the lymphatic system and general blood flow.
A person needs to receive about 50-100 grams of fat from food every day, which depends on the condition of the body and the level of physical activity.
Classification
Classification of lipids depending on their ability to form soaps under certain conditions divides them into the following classes of lipids:
- Saponifiable. This is the name for substances that, in an alkaline environment, form salts of carboxylic acids (soaps). This group includes simple lipids, complex lipids. Both simple and complex lipids are important for the body; they have different structure and, accordingly, lipids perform different functions.
- Unsaponifiable. In an alkaline environment they do not form salts of carboxylic acids. Biological chemistry includes fatty acids, derivatives of polyunsaturated fatty acids - eicosanoids, cholesterol, as the most prominent representative of the main class of sterols-lipids, as well as its derivatives - steroids and some other substances, for example, vitamins A, E, etc.
General classification of lipids
Fatty acid
Substances that belong to the group of so-called simple lipids and are of great importance for the body are fatty acids. Depending on the presence of double bonds in the non-polar (water-insoluble) carbon “tail”, fatty acids are divided into saturated (do not have double bonds) and unsaturated (have one or even more carbon-carbon double bonds). Examples of the first: stearic, palmitic. Examples of unsaturated and polyunsaturated fatty acids: oleic, linoleic, etc.
It is unsaturated fatty acids that are especially important for us and must be supplied with food.
Why? Because they:
- They serve as a component for the synthesis of cell membranes and participate in the formation of many biologically active molecules.
- Help maintain normal functioning of the endocrine and reproductive systems.
- Help prevent or slow down the development of atherosclerosis and many of its consequences.
Fatty acids are divided into two large groups: unsaturated and saturated
Inflammatory mediators and more
Another type of simple lipids are: important mediators internal regulation, like eicosanoids. They have a unique (like almost everything in biology) chemical structure and, accordingly, unique Chemical properties. The main basis Arachidonic acid, which is one of the most important unsaturated fatty acids, is used for the synthesis of eicosanoids. It is eicosanoids that are responsible for the course of inflammatory processes in the body.
Their role in inflammation can be briefly described as follows:
- They change the permeability of the vascular wall (namely, they increase its permeability).
- Stimulate the release of leukocytes and other cells immune system in fabric.
- By using chemical substances mediate the movement of immune cells, the release of enzymes and the absorption of particles foreign to the body.
But the role of eicosanoids in the human body does not end there; they are also responsible for the blood coagulation system. Depending on the current situation, eicosanoids can dilate blood vessels, relax smooth muscles, reduce aggregation or, if necessary, cause the opposite effects: vasoconstriction, contraction of smooth muscles. muscle cells and thrombus formation.
Eicosanoids are a large group of physiologically and pharmacologically active compounds.
Studies have been conducted that show that people sufficient quantity who received the main substrate for the synthesis of eicosanoids ─ arachidonic acid ─ with food (located in fish oil, fish, vegetable oils) suffered less from cardiovascular diseases. Most likely, this is due to the fact that such people have a more advanced eicosanoid metabolism.
Substances of complex structure
Complex lipids are a group of substances that are no less important for the body than simple lipids. The main properties of this group of fats:
- They participate in the formation of cell membranes, along with simple lipids, and also provide intercellular interactions.
- They are part of the myelin sheath of nerve fibers, necessary for the normal transmission of nerve impulses.
- They are one of the important components surfactant ─ a substance that ensures breathing processes, namely preventing the collapse of the alveoli during exhalation.
- Many of them play the role of receptors on the surface of cells.
- The significance of some complex fats secreted from cerebrospinal fluid, nervous tissue, cardiac muscle is not fully understood.
The simplest representatives of lipids in this group include phospholipids, glyco- and sphingolipids.
Cholesterol
Cholesterol is a substance of lipid nature with the most important value in medicine, since disruption of its metabolism negatively affects the condition of the entire organism.
Some of the cholesterol is ingested with food, and some is synthesized in the liver, adrenal glands, gonads and skin.
It is also involved in the formation of cell membranes, the synthesis of hormones and other chemicals. active substances, and also participates in lipid metabolism in the human body. Indicators of cholesterol in the blood are often examined by doctors, as they show the state of lipid metabolism in the human body as a whole.
Lipids have their own special transport forms - lipoproteins. With their help, they can be transported through the bloodstream without causing embolism.
Violations fat metabolism They are most quickly and clearly manifested by disorders of cholesterol metabolism, the predominance of atherogenic carriers (the so-called low- and very low-density lipoproteins) over anti-atherogenic ones (high-density lipoproteins).
The main manifestation of the pathology of lipid metabolism is the development of atherosclerosis.
It manifests itself by narrowing the lumen of arterial vessels throughout the body. Depending on the predominance in blood vessels various localizations narrowing of the lumen develops coronary vessels(accompanied by angina), cerebral vessels (with impaired memory, hearing, possible headaches, noise in the head), kidney vessels, blood vessels lower limbs, vessels of the digestive organs with corresponding symptoms.
Thus, lipids are at the same time an indispensable substrate for many processes in the body and, at the same time, if lipid metabolism is disturbed, they can cause many diseases and pathological conditions. Therefore, fat metabolism requires monitoring and correction when the need arises.
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