Carbohydrates: norm, types, carbohydrate metabolism, biological importance

Carbohydrates, or as they are also called – saccharides, is a unifying name for organic compounds that include carbons themselves, as well as hydrogen and oxygen compounds.

Saccharides are rightfully considered the main source of energy resources of the body - they supply energy almost instantly, but do not store it, unlike fats, which control the supply of more than 80% of energy resources, and proteins, which store energy in skeletal muscles.

Due to their species diversity, saccharides can perform many functions in the human body; their biological role in metabolic processes is extremely important.

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Carbohydrates, role and biological significance

• Saccharides take part in the construction of body cells.
• Carbohydrates, when oxidized, provide energy to the body. The oxidation of just one gram of carbohydrates releases 4 kilocalories.
• Saccharides can act as a protection for cell walls.
• Carbohydrate compounds participate in the regulation of osmosis (osmotic pressure).
• Carbohydrates are part of the structure of some monosaccharides (ribose, pentose), participating in the construction of adenosine triphosphate (ATP).
• Oligosaccharides have receptor (perceiving) properties.

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How do carbohydrates work?

1. All saccharides are the best "fuel" and source of energy for normal, active functioning of the body. Perhaps for the brain, or rather for its nutrition and vital functions, there is no more important component than carbohydrates.
2. Sources of carbohydrates can include sugar, honey, corn syrup, some types of vegetables, dairy products, flour products, and beans.
3. In the body, the transformation of saccharides into the main type of "fuel" - glucose - occurs. There are carbohydrates that, when broken down, turn into glucose quickly, and there are those that take a little longer to digest, which means that the flow of glucose into the blood will be gradual.
4. Glucose penetrates into cells with the help of insulin, some of the saccharides are deposited in the liver as a reserve for possible active actions. If the reserve norm is exceeded, or this reserve is not used (sedentary lifestyle), fatty tissue begins to form.

Types of carbohydrates

Carbohydrates are classified into the following categories:

• Simple
  • Monosaccharides are galactose, fructose, glucose
  • Disaccharides are lactose and sucrose
• Complex (polysaccharides) – fiber (fibrous saccharides), starch and glycogen.

Simple sugars are absorbed very quickly and are soluble in water; this is the familiar sugar and other products that contain it.

Among carbohydrates, glucose, which is part of almost all types of fruits and berries, occupies an "honorable" place. Glucose is a monosaccharide that, when absorbed, stimulates the production of glycogen. Glucose is a saccharide necessary for the body, which supplies nutrition to muscles, the brain, maintains the balance of sugar in the bloodstream and controls the level of glycogen reserves in the liver.

Fructose is essentially very similar in functions and properties to glucose, and is considered an easily digestible sugar, which differs from glucose only in that it is excreted more quickly and does not have time to be fully absorbed by the body. Saturation of the liver with fructose is not dangerous, moreover, fructose is more easily transformed into glycogen than glucose. There cannot be an excess of fructose in the blood in principle, since it quickly leaves the blood.

Sucrose is the type of carbohydrate that promotes fat accumulation, causing all nutrients, even protein, to turn into lipids. Sucrose is actually the progenitor of fructose and glucose, which are “born” during the hydrolysis of sucrose.

The amount of sucrose is, to some extent, an indicator of fat metabolism in the body. Also, excess sugar will sooner or later affect the composition of the blood serum and the state of the intestinal microflora. The intestinal microflora is initially populated by microorganisms, the amount of which is regulated by the acid-base and enzymatic process. Exceeding the level of sucrose leads to rapid proliferation of mycobacteria, which is a risk of dysbacteriosis and other dysfunctions of the digestive tract.

Galactose is a rare monosaccharide that is not found in food as an independent component. Galactose is produced only during the breakdown, dissimilation of milk carbohydrate – lactose.

Carbohydrate metabolism

Carbohydrates are able to deliver energy to the body quickly and efficiently, and in such a way that essential amino acids, from the remains of which proteins are created, are not used. If a person receives a sufficient amount of saccharides with food, his protein-carbohydrate metabolism is in a normal state.

If saccharides do not come from outside, the body begins to form them from glycerol and its own organic acids (amino acids), using reserves of proteins and fats, ketosis develops - oxidation of the blood, up to a persistent metabolic disorder.

If carbohydrates in the form of sugars enter the body in excessively large quantities, they do not have time to break down into glycogens and are converted into triglycerides, causing the accumulation of fat. The species diversity of saccharides is also important for normal carbohydrate metabolism; special attention should be paid to the balance of sugars, glycogen and starch (slowly absorbed carbohydrates).

There are three types of saccharide metabolism:

1. Synthesis of glycogen in the liver and muscles from glucose – glycogenesis
2. Synthesis of glycogen from proteins and fatty acids – gluconeogenesis
3. Breakdown of sugars (glucose and others), energy production – glycolysis

Carbohydrate metabolism directly depends on the amount of glucose in the blood. The glucose level in turn depends on the diet, since glucose enters the body only with food. The minimum sugar content in the blood is usually in the morning, and carbohydrate metabolism is correspondingly low. While a person sleeps, sugar intake is regulated by glycogen reserves (glycolysis and gluconeogenesis).

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Carbohydrate standards

The need for saccharides depends on many factors - gender, age, type of work, health. The average daily norm for women is 300-350 grams, for men it is higher - 400-450 grams. Easily digestible carbohydrates should be excluded from the diet in diabetes, exacerbation of coronary heart disease, minimized in atherosclerosis, allergies, hypothyroidism and gallbladder diseases.

Carbohydrates in the form of fiber, despite their popularity, should also comply with the norm - no more than 30-35 grams per day, both for men and women. Patients with exacerbation of gastrointestinal diseases should be especially careful with fiber. Fiber can be consumed without restrictions in diabetes, obesity, constipation.

The proportion of starchy sugars and glycogen in the diet should be at least 80% of the total food volume, since these carbohydrates are broken down in the digestive tract gradually and do not provoke the production of fats.

The so-called "harmful" saccharides are contained in sugar, all flour and pasta products, with the exception of products made from coarse flour (or with the addition of bran). More useful and energy-intensive carbohydrates are found in dried fruits, honey, milk and dairy products, fruits and berries.