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Carbohydrates



Biological role. Carbohydrates in nutrition play an extremely important role.

1. Carbohydrates are a good energy material.

2. The plastic function of carbohydrates is small, but they are part of some tissues and body fluids.

3. The regulatory function of carbohydrates is that they counteract the accumulation of ketone bodies during the oxidation of fats (in violation of carbohydrate metabolism (diabetes mellitus) acidosis develops).

4. Carbohydrates give the food a sweet taste, tone the central nervous system.

5. Carbohydrates have a biological activity (heparin prevents blood from clotting in the vessels, hyaluronic acid prevents bacteria from entering through the cell membrane).

6. The role of carbohydrates in defensive reactions (especially in the liver): glucuronic acid combines with toxic substances, forming non-toxic esters, soluble in water (removed with urine).

Food carbohydrates are divided into simple and complex.

Simple carbohydrates include monosaccharides (glucose, fructose) and disaccharides (sucrose, lactose, maltose). Complex carbohydrates include polysaccharides (starch, glycogen, pectin, fiber).

Simple sugars are absorbed very quickly and burn quickly, releasing energy. This property is successfully used by athletes to maintain a high but short-term performance (for example, when running for short distances).

The biological role of monosaccharides.

Glucose is the most important structural unit from which polysaccharides are built (starch, glycogen, fiber). Glucose is a part of disaccharides - sucrose, lactose, maltose. It is rapidly absorbed into the blood and is used as a source of energy during heavy physical exertion. Glucose is involved in the formation of glycogen, nutrition of the brain tissue, working muscles (especially the heart muscle). Glucose easily turns into fats in the body, especially when it is excessive intake from food.

Sources of glucose: fruits and berries (grapes, persimmon, bananas, apples, peaches, etc.), as well as honey, where glucose contains up to 37%.

Fructose has the same properties as glucose, but it is absorbed more slowly in the intestine and, entering the blood, leaves it quickly, without causing oversaturation of blood with sugar. This property of fructose is used for diabetes. Fructose is much faster than glucose, turns into glycogen. There is its best tolerability compared with other sugars. Fructose is almost 2 times sweeter than sucrose, 3 times sweeter than glucose.

If you take the sweetness of sucrose as 100, then the sweetness of fructose will be 173, glucose - 74, xylose - 40, invert sugar - 130, maltose - 32.5, galactose - 32.1, lactose - 16. The high sweetness of fructose allows you to use it in small quantities, which is of great importance for diets of limited calories.

Sources of fructose: fruits and berries (persimmon, bananas, grapes, apples, pears, black currants, peaches, raspberries, watermelons, cantaloupe), bee honey. In watermelon, melon, apple, pear, black currant, fructose prevails over glucose.

The biological role of disaccharides.

Sucrose in the gastrointestinal tract breaks down into glucose and fructose. Sucrose is the most common sugar. Sources of sucrose: sugar beet (14-18%) and sugar cane (10-15%). Sucrose content: in sugar sand - 99.75%, in refined sugar - 99.9%.

Sucrose has the ability to turn into fat. Excessive intake of this carbohydrate in the diet causes a violation of fat and cholesterol metabolism in the human body, has a negative effect on the condition and function of the intestinal microflora, increasing the proportion of putrefactive microflora, increasing the intensity of putrefactive processes in the intestines, leads to the development of intestinal meteorism.
Excessive amounts of sucrose in the diet of children leads to the development of dental caries.

Lactose is a carbohydrate of animal origin. During hydrolysis is split into glucose and galactose. Hydrolysis proceeds slowly, limiting the fermentation process, which is of great importance in the nutrition of infants. Intake of lactose in the body contributes to the development of lactic acid bacteria that suppress the development of putrefactive microorganisms. Lactose is the least used for fat formation and does not increase cholesterol levels in the blood with an excess. Lactose source: milk and dairy products, in which the content of this disaccharide can reach 4-6%.

The biological role of polysaccharides.

Starch. It accounts for about 80% of the total amount of carbohydrates consumed. Starch in the human body is the main source of glucose. Starch constitutes the main part of the carbohydrates of bread and bakery products, flour, various cereals, potatoes.

Glycogen is a carbohydrate reserve of animal tissue. An excess of carbohydrates from food is converted into glycogen, which is deposited in the liver, forming a depot of carbohydrates used for various physiological functions - an important role in regulating blood sugar levels. The total glycogen content is about 500 g. If carbohydrates do not come from food, then its reserves are exhausted after 12-18 hours. In connection with the depletion of carbohydrate reserves, the processes of fatty acid oxidation are enhanced. Depletion of the liver with glycogen leads to the occurrence of fatty infiltration, and then to fatty degeneration of the liver.

Sources of glycogen: liver, meat, fish.

Pectic substances. There are pectins and protopectins.

Propectin - a combination of pectin with cellulose. It is contained in the cell walls of plants, insoluble in water. The rigidity of immature fruits is explained by the significant content of protopectin in them. In the process of maturation the protopectin splits and the fruits become soft, at the same time they are enriched with pectin.

Pectin is an integral part of cell sap and is characterized by good digestibility. Pectic substances have the property to inhibit the activity of the putrefactive intestinal microflora. Pectin is used in treatment-and-prophylactic nutrition for people working with lead and other toxic substances.

Pectic substances are found in apricots, oranges, cherries, plums, apples, pears, quince, pumpkins, carrots, radishes.

Cellulose (cellulose) forms cell walls and is a supporting substance. The important role of cellulose as a stimulator of intestinal peristalsis, an adsorbent of sterols, including cholesterol, prevents their reabsorption and removal from the body. Fiber plays a role in the normalization of the composition of the intestinal microflora, in reducing putrefactive processes, and prevents the absorption of toxic substances.

Cellulose is contained in: potatoes (1%), fruits and fruits (0.5-1.3%), vegetables (0.7-2.8%), buckwheat (2%).

The average carbohydrate requirement is 400-500 g / day, which is 1: 1: 4 (for children) and 1: 1.25: 5 (for adults) with respect to proteins and fats. At the same time, in the total amount of carbohydrates, 350400 g should be used for starch, 50-100 g for mono- and disaccharides, and 25.25 g for food-grade ballast substances (cellulose and pectic substances).

Excessive sugar intake contributes to the development of dental caries, disruption of the normal ratio of excitatory and inhibitory processes in NA, supports inflammation, and promotes allergization of the body.

It is necessary to limit carbohydrates for the following diseases:

1) diabetes;

2) obesity;

3) allergies, skin diseases;

4) inflammatory processes.

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Carbohydrates

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