Carbohydrates are one of the key sources of energy for our body. Today we will look at the types and functions of carbohydrates, as well as find out what foods they contain.
Why does a person need carbohydrates?
Before considering the types of carbohydrates, let's look at their functions. The human body always has a carbohydrate reserve in the form of glycogen. It is about 0.5 kg. 2/3 of this substance is in muscle tissue, and another third is in the liver. Between meals, glycogen is broken down into glucose, thereby leveling the fluctuations in blood sugar levels.
Without the intake of carbohydrates, glycogen stores run out after 12-18 hours. If this happens, carbohydrates begin to form from the intermediate products of protein metabolism. These substances are vital for a person, since they, mainly due to the oxidation of glucose, form energy in our tissues.
Deficit
With a chronic carbohydrate deficiency, the glycogen store in the liver is depleted, and fats begin to be deposited in its cells. This leads to degeneration of the liver and disruption of its functions. When a person consumes an insufficient amount of carbohydrates with food, his organs and tissues begin to usefor energy synthesis, not only protein, but also fat. Increased breakdown of fats leads to disruption of metabolic processes. The reason for this is the accelerated formation of ketones (the most famous of them is acetone) and their accumulation in the body. When ketones are formed in excess, the internal environment of the body "acidifies", and brain tissue gradually begins to poison.
Excess
Like a deficiency, an excess of carbohydrates does not bode well for the body. If a person takes in too many carbohydrates, their insulin and blood glucose levels rise. As a result, fatty deposits are formed. It happens in the following way. When a person does not eat all day after breakfast, and in the evening, after coming home from work, decides to take lunch, afternoon snack and dinner at the same time, the body tries to deal with excess carbohydrates. This is how blood sugar levels rise. Insulin is needed to move glucose from the blood to tissue cells. It, in turn, getting into the bloodstream, stimulates the synthesis of fats.
In addition to insulin, carbohydrate metabolism is regulated by other hormones. Glucocorticoids are hormones of the adrenal cortex that stimulate the synthesis of glucose from amino acids in the liver. The same process is enhanced by the hormone glucagon. The functions of glucocorticoids and glucagon are opposite to insulin.
Norma
According to the norms, carbohydrates should be 50-60% of the calorie content of food. It is impossible to exclude them from the diet, despite the fact that they are partly "guilty" in the formation of extra pounds.
Carbohydrates: types, properties
By its chemical structureCarbohydrates are divided into simple and complex. The former are mono- and disaccharides, and the latter are polysaccharides. Let's analyze both classes of substances in more detail.
Simple carbohydrates
Glucose. We begin to consider simple types of carbohydrates with the most important of them. Glucose acts as a structural unit of the main amount of poly- and disaccharides. During metabolism, it breaks down into monosaccharide molecules. They, in turn, in the course of a complex reaction, turn into substances that are oxidized to water and carbon dioxide, which are fuel for cells.
Glucose is an important component in carbohydrate metabolism. When blood levels drop or high concentrations make it impossible for the body to function properly (as is the case with diabetes), the person experiences drowsiness and may pass out (hypoglycemic coma).
In its pure form, glucose (as a monosaccharide) is found in a large number of vegetables and fruits. The following fruits are especially rich in this substance:
- grapes – 7.8%;
- cherries and sweet cherries - 5.5%;
- raspberries - 3.9%;
- strawberries - 2.7%;
- watermelon and plum – 2.5%.
Among vegetables rich in glucose are: pumpkin, white cabbage and carrots. They contain about 2.5% of this component.
Fructose. It is one of the most common fruit carbohydrates. It, unlike glucose, can penetrate from the blood into tissues without the participation of insulin. Therefore, fructose is considered the optimal source of carbohydrates for people suffering fromdiabetes. Some of it goes to the liver, where it turns into glucose - a more versatile "fuel". Such a substance can also increase blood sugar levels, but not as much as other simple carbohydrates. Fructose is converted to fat more easily than glucose. But its main advantage is that it is 2.5 and 1.7 times sweeter than glucose and sucrose, respectively. Therefore, this carbohydrate is used instead of sugar in order to reduce the calorie content of food.
Most of all fructose is found in fruits, namely:
- grapes – 7.7%;
- apples - 5.5%;
- pears - 5.2%;
- cherries and sweet cherries - 4.5%;
- watermelons – 4.3%;
- blackcurrant – 4.2%;
- raspberries - 3.9%;
- strawberries - 2.4%;
- melon – 2.0%.
Vegetables contain less fructose. Most of all it can be found in white cabbage. In addition, fructose is present in honey - about 3.7%. It is known for certain that it does not cause cavities.
Galactose. Considering the types of carbohydrates, we have already met with some of the simple substances that can be found in foods in a free form. Galactose is not. It forms a disaccharide with glucose called lactose (aka milk sugar), the main carbohydrate in milk and products derived from it.
In the gastrointestinal tract, lactose is broken down by the enzyme lactase into glucose and galactose. Some people have milk intolerance associated with a lack of milk in the body.lactase. In its unsplit form, lactose is a good nutrient for the intestinal microflora. In fermented milk products, the lion's share of this substance is fermented to lactic acid. Thanks to this, people who have lactase deficiency can consume fermented milk products without unpleasant consequences. In addition, they contain lactic acid bacteria that inhibit the activity of the intestinal microflora and neutralize the effects of lactose.
Galactose, the formation of which occurs during the breakdown of lactose, is converted into glucose in the liver. If a person lacks the enzyme that is responsible for this process, he may develop a disease such as galactosemia. Cow's milk contains 4.7% lactose, cottage cheese - 1.8-2.8%, sour cream - 2.6-3.1%, kefir - 3.8-5.1%, yogurt - about 3%.
Sucrose. On this substance, we will finish our consideration of simple types of carbohydrates. Sucrose is a disaccharide that is made up of glucose and fructose. Sugar contains 99.5% sucrose. Sugar is rapidly broken down by the gastrointestinal tract. Glucose and fructose are absorbed into the human blood and serve not only as a source of energy, but also as the most important precursor of glycogen in fat. Because sugar is a pure carb with no nutrients, many refer to it as a source of “empty calories.”
Beets are the richest product in sucrose (8.6%). Among other vegetable fruits, one can single out peach - 6%, melon - 5.9%, plum - 4.8%,tangerine - 4.5%, carrots - 3.5%. In other vegetables and fruits, the sucrose content ranges from 0.4-0.7%.
A few words should also be said about m altose. This carbohydrate is made up of two glucose molecules. M altose (m alt sugar) is found in honey, molasses, confectionery, m alt and beer.
Complex carbohydrates
Now let's discuss the types of complex carbohydrates. These are all polysaccharides that are found in the human diet. With rare exceptions, glucose polymers can be found among them.
Starch. It is the main carbohydrate digested by humans. 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 lowest starch content is observed in oatmeal - 49%. Pasta contains up to 68% of this carbohydrate. In wheat bread, starch is 30-50%, and in rye bread - 33-49%. This carbohydrate is also found in legumes - 40-44%. Potatoes contain up to 18% starch, so nutritionists sometimes classify them not as vegetables, but as starchy foods, like grains with legumes.
Inulin. This polysaccharide is a polymer of fructose, which 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 referred to as "animal starch". It consistsfrom branched glucose molecules and is found in animal products, namely: liver - up to 10% and meat - up to 1%.
Conclusion
Today we looked at the main types of carbohydrates and found out what functions they perform. Now our approach to nutrition will be more meaningful. Brief summary of the above:
- Carbohydrates are an important source of energy for humans.
- Too much is just as bad as too little.
- Types of carbohydrates: simple, complex.
- Simple are mono- and disaccharides, and complex are polysaccharides.
