Food consumed by man, it is necessary to design and functioning of his body. In addition, nutrition is of great importance from the viewpoint of preventive medicine. In the past, doctors had to deal mainly with the effects of malnutrition, their attention is now increasingly require the display of overeating. Too much food leads to obesity, which are often companions "diseases of civilization", and a decrease in life expectancy. Let us first consider what information science now has the composition and value of the foods we eat.
The energy contained in food in the form of nutrients - proteins, fats and carbohydrates. Rule isodynam: How energy nutrients are interchangeable according to their caloric value. But the nutrients in the body do not only energy, but plastic function that is used for the synthesis of structural components of the body. Therefore, the diet must include a minimum number of proteins, fats and carbohydrates! After a meal increases the intensity of metabolism. In the case of a mixed meal metabolic rate increases by about 6%. If protein consumption rate of metabolism increases at a much greater extent than after administration of fat or carbohydrates.
Protein - a substance composed of amino acids. They are required for the body to the synthesis of compounds that form the structure and ensure normal functioning. The composition of food must include proteins containing so-called essential amino acids (those that can not synthesize our body, or they are synthesized in adequate quantities.) In humans, most of the proteins used for exchange of plastic, that is for the construction and renovation of biological structures (muscles, enzymes, hormones, blood plasma proteins, etc.). In this regard, proteins can not be replaced by fat or carbohydrates.
Fats are usually a mixture of different triglycerides (esters of glycerol and fatty acids). Fatty acids are saturated and unsaturated. Some fatty acids necessary for the life of the organism, are indispensable, they are necessary, including the synthesis of phospholipids - "building blocks" involved in the construction of cell membranes and mitochondria. Of the indispensable man for the most essential linoleic acid. After absorption of fat or undergo oxidation (and become sources of energy), or deposited in the tissues as a reserve of energy.
Cholesterol is found only in animal organisms. A sufficient amount of cholesterol the body needs, but the excess of its presence in the blood (hypercholesterolemia), which is often obesity, is a risk factor for several diseases (cardiovascular, metabolic). Cholesterol is inextricably linked with the consumption of his - on his level in the blood affects not only the consumption of the cholesterol, but other fats: saturated fatty acids contribute to the concentration of cholesterol in the blood, and unsaturated - reduction.
Carbohydrates are the main source of energy for cells. The energy requirements of the brain are provided almost entirely by glucose. She not only performs the function of energy, but also used as building material for the synthesis of many important substances. At the same time, the muscles in insufficient intake of sugar can metabolize fatty acids (it is their property is used in low-carb diets). In the body, carbohydrates are stored as glycogen (in muscle, liver).