For our body, carbohydrates are one of the key sources of energy. Today, we will look at the types and functions of carbohydrates, and we also find out what foods they contain.
Why does man need carbohydrates?
Before considering the types of carbohydrates, we will understandwith their functions. In the human body, there is always a carbohydrate reserve in the form of glycogen. It is about 0.5 kg. 2/3 of this substance is in muscle tissues, and a third - in the liver. In the intervals between meals, glycogen breaks down into glucose, thereby leveling the fluctuations in the sugar content in the blood.
Without the intake of carbohydrates in storesglycogen ends after 12-18 hours. If this happens, carbohydrates begin to form from the intermediate products of protein metabolism. These substances are vital for man, since they, mainly due to the oxidation of glucose, form energy in our tissues.
Deficiency
With a chronic shortage of carbohydratesglycogen in the liver is depleted, and fats begin to be deposited in its cells. This leads to the degeneration of the liver and the violation of its functions. When a person consumes an inadequate amount of carbohydrates with food, his organs and tissues begin to use not only protein, but also fat to synthesize energy. The increased disintegration of fats leads to disruption of metabolic processes. The reason for this - the accelerated formation of ketones (the most famous of them - acetone) and their accumulation in the body. When ketones are formed in excess, the internal environment of the body "becomes acidic," and the brain tissue gradually begins to be poisoned.
Excess
Like deficiency, excess carbohydrates do not bode wellorganism. If a person takes too many carbohydrates with food, the level of insulin and glucose in the blood rises. As a result, fat deposits form. There is it as follows. When a person after breakfast does not eat all day, and in the evening, coming home from work, decides to take lunch, afternoon tea and dinner at the same time, the body tries to fight with an excess of carbohydrates. So there is an increase in the level of sugar in the blood. To glucose from the blood passed into the cells of tissues, you need insulin. He, in turn, getting into the blood, gives an incentive to synthesize fats.
In addition to insulin, the metabolism of carbohydrates is regulated andother hormones. Glucocorticoids are the hormones of the adrenal cortex that stimulate the synthesis of glucose from the amino acids in the liver. The same process is intensified by hormone glucagon. By function, glucocorticoids and glucagon are the opposite of insulin.
Norm
According to the norms, carbohydrates should be 50-60% of the calorie content of food. It is impossible to exclude them from the diet, in spite of the fact that they are partly "guilty" in the formation of extra kilograms.
Carbohydrates: types, properties
By its chemical structure carbohydrates are divided into simple and complex. The first include mono- and disaccharides, and the second - polysaccharides. Let's analyze both classes of substances in more detail.
Simple carbohydrates
Glucose. We begin to consider simple types of carbohydrates withthe most important of them. Glucose acts as a structural unit of the main quantity of poly- and disaccharides. In the course of metabolism, it decomposes into monosaccharide molecules. They, in turn, during a complex reaction turn into substances oxidized to water and carbon dioxide, which are fuel for cells.
Glucose is an important component in carbohydrateexchange. When his blood level drops or high concentration makes the normal functioning of the body impossible (as in the case of diabetes), a person experiences drowsiness and may lose consciousness (hypoglycemic coma).
In its pure form, glucose (as a monosaccharide) is found in a large number of vegetables and fruits. Especially this substance is rich in such fruits:
- grapes - 7.8%;
- cherry and sweet cherry - 5,5%;
- raspberry - 3.9%;
- strawberries - 2.7%;
- watermelon and plum - 2,5%.
Among the vegetables rich in glucose, you can note: a pumpkin, cabbage and carrots. They contain about 2.5% of this component.
Fructose. This is one of the most common fruitcarbohydrates. It, in contrast to glucose, can penetrate from the blood into the tissues without the participation of insulin. Therefore, fructose is considered the optimal source of carbohydrates for people with diabetes. Its part gets to the liver, where it turns into glucose - a more universal "fuel". Such a substance can also increase the blood sugar level, but not as much as other simple carbohydrates. Fructose is converted to fats more easily than glucose. But its main advantage is that it is sweeter than glucose and sucrose in 2.5 and 1.7 times, respectively. Therefore, this carbohydrate is used in place of sugar in order to reduce the calorie content of food.
Most of the fructose is found in fruits, namely:
- grapes - 7.7%;
- apples - 5,5%;
- pears - 5,2%;
- cherry and cherry - 4,5%;
- watermelons - 4,3%;
- black currant - 4.2%;
- raspberry - 3.9%;
- strawberries - 2.4%;
- melon - 2.0%.
In vegetables, fructose contains less. Most of all, it can be found in white cabbage. In addition, fructose is present in honey - about 3.7%. It is well known that it does not cause caries.
Galactose. Considering the types of carbohydrates, we have alreadygot acquainted with some simple substances that can be found in products in a free form. Galactose is not. It forms a disaccharide with glucose, which is called lactose (which is milk sugar), the main carbohydrate of milk and products derived from it.
In the gastrointestinal tract, lactoseThe enzyme lactase is split into glucose and galactose. Some people have milk intolerance associated with a lack of lactase in the body. In unsplit form, lactose is a good nutrient for the intestinal microflora. In sour-milk products, the lion's share of this substance is fermented to lactic acid. Thanks to this, people who have lactase deficiency can eat acid-free products without unpleasant consequences. In addition, they have lactic acid bacteria that suppress the activity of the intestinal microflora and neutralize the effects of lactose.
Galactose, the formation of which occurs whendecay of lactose, in the liver is converted into glucose. If a person lacks an enzyme that is responsible for the process, he may develop a disease such as galactosemia. Cow's milk contains 4.7% lactose, in curd - 1.8-2.8%, in sour cream - 2.6-3.1%, in kefir - 3.8-5.1%, in yogurt - about 3%.
Sucrose. On this substance we finish examiningsimple types of carbohydrates. Sucrose is a disaccharide, which consists of glucose and fructose. The sugar contains 99.5% sucrose. Sugar is rapidly broken down by the gastrointestinal tract. Glucose with fructose are absorbed into the human blood and serve not only as an energy source, but also the most important precursor of glycogen in fat. Since sugar is carbohydrates in its pure form, not containing nutrients, many people call it a source of "empty calories."
Beet - the most rich in sucrose product (8.6%).Other plant fruits include peach - 6%, melon - 5.9%, plum - 4.8%, mandarin - 4.5%, carrots - 3.5%. In other vegetables and fruits, the content of sucrose varies between 0.4 and 0.7%.
A couple of words worth mentioning about maltose. This carbohydrate consists of two molecules of glucose. Maltose (malt sugar) is found in honey, molasses, confectionery, malt and beer.
Complex carbohydrates
Now we will discuss the types of complex carbohydrates. These are called all polysaccharides, which are found in the human diet. With a few exceptions, one can find polymers of glucose among them.
Starch. This is the main carbohydrate, digested by man.It accounts for 80% of carbohydrates consumed with food. Starch is found in potatoes and cereal products, namely: cereals, flour, bread. Most of this substance can be found in rice - 70% and buckwheat - 60%. Among cereals, the smallest content of starch is found in oatmeal - 49%. In pasta contains up to 68% of this carbohydrate. In wheat bread, starch is 30-50%, and in rye - 33-49%. This carbohydrate is also found in legumes - 40-44%. In potato contains up to 18% of starch, so nutritionists sometimes refer it not to vegetables, but to starchy foods, like grains and legumes.
Inulin. This polysaccharide is a fructose polymer that is found in Jerusalem artichoke and, to a lesser extent, in other plants. Products containing inulin are prescribed for diabetes and its prevention.
Glycogen. It is often called "animal starch." It consists of branched glucose molecules and is found in animal products, namely: liver - up to 10% and meat - up to 1%.
Conclusion
Today we reviewed the main types of carbohydrates and learned what functions they perform. Now our approach to nutrition will be more meaningful. Brief summary of the foregoing:
- Carbohydrates are an important source of energy for humans.
- Their excess is just as bad as the defect.
- Types of carbohydrates: simple, complex.
- Mono and disaccharides belong to simple ones, and polysaccharides to complex ones.
