07.04.2009
Fats make up approximately 44 percent of the diet. Recommendations about proper diet It is advised that this figure should not exceed 30 percent of total calories, and 25 percent would be even better.
Your fat intake should lean towards polyunsaturated and mono unsaturated fats With maximum number saturated fat no more than 10 percent or less of that total 25 percent fat.
* To reduce the fat content when preparing an omelet, remove the yolk of every second egg, this will reduce fat and cholesterol levels, and you will not even feel the difference.
*Cottonseed oil is 25 percent saturated fat and is not the best to use.
* Soybean oil changes taste when long-term storage, due to changes in the levels of linolenic acid it contains.
* Sixty-four percent of the calories from caviar come from fat.
*Butter absorbs refrigerator odors, so it should be stored in a closed container.
* Butter can be stored in the refrigerator for only two weeks. If you need to save it for more long time, store in the freezer.
*Eight ounces of potato chips equals consuming 12 to 20 teaspoons of fat.
*Try using water instead of fat in some recipes. It is true that fats make dressings, etc., the taste becomes smooth, but if you mix water with flour, with corn starch (corn meal) or potato starch, it will save you from extra calories.
* Oils should be stored in dark containers and stored in a dark, cool place to reduce the risk of rancidity.
* When carob is made into candy, fat is added for texture, making the fat level close to that of real chocolate. In fact, the cocoa butter used in chocolate production is 60 percent saturated fat, while the fat in carob candies is, in most cases, 85 percent saturated fat.
*Using non-stick cookware and vegetable oil sprays will reduce fat consumption.
* Never eat mayonnaise-based salad dressing or salad unless you are sure it has been refrigerated until you are ready to eat it. Neglecting this is responsible for thousands of cases of food poisoning every year.
* Fish-related oils are more beneficial than meat-related oils. Fish contains a high percentage of omega fatty acids.
* Any margarine containing coconut or Palm oil will have a very high level saturated fat content. Labels now call them tropical oils (tropical plant oils).
* New fat substitutes continue to appear in our products. Don't forget that they are still synthetic and not natural product. They should not be seen as a panacea for replacing fat in our diet.
*Best butter Made from AA grade sweet cream.
*An ounce of sunflower seeds contains 160 calories and is not considered a dietary snack.
* A burrito topped with sour cream and guacamole (a sauce made from mashed avacado, tomatoes, spices and mayonnaise) can contain up to 1,000 calories and 59 percent fat.
* Research has shown that stearic acid, a saturated fat, has little effect on raising cholesterol levels.
*The new reduced-fat peanut butter has the same number of calories per serving as regular peanut butter, approximately 190 calories per serving, and has been added with sweeteners instead of fat.
* When you store some oils in the refrigerator, they may become cloudy (not clear, light cloudy), this is due to the formation of harmless crystals. Manufacturers sometimes refrigerate oils before releasing them for sale and remove these crystals in a process called “winterizing.” Now these oils will remain clear when cooled.
* Pork fat has large crystals, whereas butter small size. This is highly dependent on the texture of the fat and can be controlled during processing. The size of the crystals can be changed by shaking (shaking) the oil while it cools.
* Studies have shown that people on a diet miss fat more than sweets.
* People on a diet with high content fats are more prone to colon cancer, prostate cancer or breast cancer. Future research may show that this also has an effect harmful effect on the immune system.
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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 animal substances 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 doing heavy lifting 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, the mass fraction of lipids is minimal, but the fatty acids included in such lipids are 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 mass fraction 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. Moreover, they only work well in 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 an 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 eating a large amount of fatty foods, the level of triglycerides in the blood may increase 2 to 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 concentration 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. Typically, venous blood is taken for this purpose. 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 research for patients with various lipid metabolism disorders, 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 a few 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 of the 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 muscle tension abdominals. 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 lipids, necessary for 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 an 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 the general bloodstream.
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 certain conditions divides them into the following classes of lipids:
- Saponifiable. This is the name for substances that, in an environment with alkaline reaction 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 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.
- With the help of chemicals, they 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 diseases of cardio-vascular system. 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 of surfactant ─ a substance that ensures breathing processes, namely, preventing the alveoli from collapsing 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.
Disorders of fat metabolism 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 of the coronary vessels develops (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.
LIPIDS - this is a heterogeneous group of natural compounds, completely or almost completely insoluble in water, but soluble in organic solvents and in each other, yielding high molecular weight fatty acids upon hydrolysis.
In a living organism, lipids perform various functions.
Biological functions of lipids:
1) Structural
Structural lipids form complex complexes with proteins and carbohydrates, from which the membranes of cells and cellular structures are built, and participate in a variety of processes occurring in the cell.
2) Spare (energy)
Reserve lipids (mainly fats) are the body's energy reserve and participate in metabolic processes. In plants they accumulate mainly in fruits and seeds, in animals and fish - in subcutaneous fatty tissues and tissues surrounding internal organs, as well as liver, brain and nervous tissues. Their content depends on many factors (type, age, nutrition, etc.) and in some cases accounts for 95-97% of all secreted lipids.
Calorie content of carbohydrates and proteins: ~ 4 kcal/gram.
Caloric content of fat: ~ 9 kcal/gram.
The advantage of fat as an energy reserve, unlike carbohydrates, is its hydrophobicity - it is not associated with water. This ensures compactness of fat reserves - they are stored in anhydrous form, occupying a small volume. The average person's supply of pure triacylglycerols is approximately 13 kg. These reserves could be enough for 40 days of fasting under conditions of moderate physical activity. For comparison: total reserves glycogen in the body - approximately 400 g; when fasting, this amount is not enough even for one day.
3) Protective
Subcutaneous adipose tissue protects animals from cooling, and internal organs from mechanical damage.
The formation of fat reserves in the body of humans and some animals is considered an adaptation to irregular nutrition and living in a cold environment. Animals that hibernate for a long time (bears, marmots) and are adapted to living in cold conditions (walruses, seals) have a particularly large reserve of fat. The fetus has virtually no fat and appears only before birth.
A special group in terms of their functions in a living organism are the protective lipids of plants - waxes and their derivatives, covering the surface of leaves, seeds and fruits.
4) An important component of food raw materials
Lipids are an important component food, largely determining its nutritional value and taste. The role of lipids in various food technology processes is extremely important. Spoilage of grain and its processed products during storage (rancidity) is primarily associated with changes in its lipid complex. Lipids isolated from a number of plants and animals are the main raw materials for obtaining the most important food and technical products (vegetable oil, animal fats, including butter, margarine, glycerin, fatty acids, etc.).
2 Classification of lipids
There is no generally accepted classification of lipids.
It is most appropriate to classify lipids depending on their chemical nature, biological functions, as well as in relation to some reagents, for example, alkalis.
Based on their chemical composition, lipids are usually divided into two groups: simple and complex.
Simple lipids – esters of fatty acids and alcohols. These include fats , waxes And steroids .
Fats – esters of glycerol and higher fatty acids.
Waxes – esters of higher alcohols of the aliphatic series (with a long carbohydrate chain of 16-30 C atoms) and higher fatty acids.
Steroids – esters of polycyclic alcohols and higher fatty acids.
Complex lipids – in addition to fatty acids and alcohols, they contain other components of various chemical natures. These include phospholipids and glycolipids .
Phospholipids are complex lipids in which one of the alcohol groups is not associated with FA, but with phosphoric acid (phosphoric acid can be combined with an additional compound). Depending on which alcohol is included in the phospholipids, they are divided into glycerophospholipids (contain the alcohol glycerol) and sphingophospholipids (contain the alcohol sphingosine).
Glycolipids – these are complex lipids in which one of the alcohol groups is associated not with FA, but with a carbohydrate component. Depending on which carbohydrate component is part of the glycolipids, they are divided into cerebrosides (they contain a monosaccharide, disaccharide or a small neutral homooligosaccharide as a carbohydrate component) and gangliosides (they contain an acidic heterooligosaccharide as a carbohydrate component).
Sometimes into an independent group of lipids ( minor lipids ) secrete fat-soluble pigments, sterols, and fat-soluble vitamins. Some of these compounds can be classified as simple (neutral) lipids, others - complex.
According to another classification, lipids, depending on their relationship to alkalis, are divided into two large groups: saponifiable and unsaponifiable. The group of saponified lipids includes simple and complex lipids, which, when interacting with alkalis, hydrolyze to form salts of high molecular weight acids, called “soaps”. The group of unsaponifiable lipids includes compounds that are not subject to alkaline hydrolysis (sterols, fat-soluble vitamins, ethers, etc.).
According to their functions in a living organism, lipids are divided into structural, storage and protective.
Structural lipids are mainly phospholipids.
Storage lipids are mainly fats.
Protective lipids of plants - waxes and their derivatives, covering the surface of leaves, seeds and fruits, animals - fats.
FATS
The chemical name of fats is acylglycerols. These are esters of glycerol and higher fatty acids. "Acyl" means "fatty acid residue".
Depending on the number of acyl radicals, fats are divided into mono-, di- and triglycerides. If the molecule contains 1 fatty acid radical, then the fat is called MONOACYLGLYCEROL. If the molecule contains 2 fatty acid radicals, then the fat is called DIACYLGLYCEROL. In the human and animal body, TRIACYLGLYCEROLS predominate (contain three fatty acid radicals).
The three hydroxyls of glycerol can be esterified either with only one acid, such as palmitic or oleic, or with two or three different acids:
Natural fats contain mainly mixed triglycerides, including residues of various acids.
Since the alcohol in all natural fats is the same - glycerol, the differences observed between fats are due solely to the composition of fatty acids.
Over four hundred carboxylic acids of various structures have been found in fats. However, most of them are present only in small quantities.
The acids contained in natural fats are monocarboxylic acids, built from unbranched carbon chains containing an even number of carbon atoms. Acids containing an odd number of carbon atoms, having a branched carbon chain, or containing cyclic moieties are present in small quantities. The exceptions are isovaleric acid and a number of cyclic acids found in some very rare fats.
The most common acids in fats contain 12 to 18 carbon atoms and are often called fatty acids. Many fats contain small amounts of low molecular weight acids (C 2 -C 10). Acids with more than 24 carbon atoms are present in waxes.
The glycerides of the most common fats contain significant quantities of unsaturated acids containing 1-3 double bonds: oleic, linoleic and linolenic. Arachidonic acid containing four double bonds is present in animal fats; acids with five, six or more double bonds are found in fats of fish and marine animals. Majority unsaturated acids lipids have a cis configuration, their double bonds are isolated or separated by a methylene (-CH 2 -) group.
Of all the unsaturated acids contained in natural fats, oleic acid is the most common. In many fats, oleic acid makes up more than half of the total mass of acids, and only a few fats contain less than 10%. Two other unsaturated acids - linoleic and linolenic acid - are also very widespread, although they are present in much smaller quantities than oleic acid. Linoleic and linolenic acids are found in noticeable quantities in vegetable oils; For animal organisms they are essential acids.
Of the saturated acids, palmitic acid is almost as widespread as oleic acid. It is present in all fats, with some containing 15-50% of the total acid content. Stearic and myristic acids are widely used. Stearic acid is found in large quantities (25% or more) only in the storage fats of some mammals (for example, in sheep fat) and in the fats of some tropical plants, such as cocoa butter.
It is advisable to divide the acids contained in fats into two categories: major and minor acids. The main acids of fat are acids whose content in fat exceeds 10%.
Physical properties of fats
As a rule, fats do not withstand distillation and decompose even if they are distilled under reduced pressure.
The melting point, and therefore the consistency of fats, depends on the structure of the acids that make up them. Solid fats, i.e. fats that melt at a relatively high temperature, consist predominantly of glycerides of saturated acids (stearic, palmitic), and oils that melt at a lower temperature and are thick liquids contain significant amounts of glycerides of unsaturated acids (oleic , linoleic, linolenic).
Since natural fats are complex mixtures of mixed glycerides, they do not melt at a certain temperature, but in a certain temperature range, and they are first softened. To characterize fats, it is usually used solidification temperature, which does not coincide with the melting point - it is slightly lower. Some natural fats are solids; others are liquids (oils). The solidification temperature varies widely: -27 °C for linseed oil, -18 °C for sunflower oil, 19-24 °C for cow lard and 30-38 °C for beef lard.
The solidification temperature of fat is determined by the nature of its constituent acids: the higher the content of saturated acids, the higher it is.
Fats are soluble in ether, polyhalogen derivatives, carbon disulfide, aromatic hydrocarbons (benzene, toluene) and gasoline. Solid fats are poorly soluble in petroleum ether; insoluble in cold alcohol. Fats are insoluble in water, but they can form emulsions that are stabilized in the presence of surfactants (emulsifiers) such as proteins, soaps and some sulfonic acids, mainly in a slightly alkaline environment. Milk is a natural fat emulsion stabilized by proteins.
Chemical properties of fats
Fats undergo all chemical reactions characteristic of esters, but their chemical behavior has a number of features associated with the structure of fatty acids and glycerol.
Among the chemical reactions involving fats, several types of transformations are distinguished.
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 in 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.
Average a common person gains 1 g of excess fat every day. 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 needed by 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 classified as unsaturated fats, such fats are essential 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.
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