Carbohydrates, also known as sugars, are an important class of natural organic compounds that are the most abundant and widely distributed in nature. Glucose, sucrose, starch and cellulose are sugar compounds.
Sugar compounds are the main source of energy needed by all organisms to sustain their life activities. It is not only a nutrient but also has some special physiological activity. For example, heparin in the liver has an anticoagulant effect; sugars in the blood group are related to immune activity. In addition, the composition of nucleic acids also contains sugar compounds - ribose and deoxyribose. Therefore, sugar compounds have a more important significance for medicine.
Sugar compounds are composed of three elements: C (carbon), H (hydrogen), and O (oxygen). The proportion of H and O in the molecule is usually 2:1, which is the same as the proportion in water molecule. Therefore, it is called carbohydrate. It can be represented by the general formula Cm(H2O)n. Therefore, these compounds have been called carbohydrates. However, it was later discovered that some compounds are sugar compounds according to their structure and properties, but their composition does not conform to the general formula of Cm(H2O)n, such as rhamnose (C6H12O5), deoxyribose (C5H10O4), etc.; and some compounds, such as Acetate (C2H4O2), lactic acid (C3H6O3), etc., although the composition of the general formula Cm (H2O) n, but the structure and properties are completely different from the sugar compound. Therefore, the name of carbohydrate is not exact, but it has been used for a long time.
Carbohydrates are the cheapest nutrients among the three major nutrients that provide the body with heat. The carbohydrates in food are divided into two categories: people can absorb the use of effective carbohydrates, such as: monosaccharides, disaccharides, polysaccharides and human indigestible ineffective carbohydrates, such as: cellulose.
Carbohydrate classification
Carbohydrates are divided into monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Sugar conjugates include three classes of glycolipids, glycoproteins, and proteoglycans.
The physiological function of carbohydrates
(1) Supply of energy: 16 kJ per gram glucose (4 kcal), carbohydrates consumed by the human body are digested into glucose or other monosaccharides in the body to participate in metabolism. The proportion of carbohydrates in each person's diet does not specify the specific amount. China's nutrition experts believe that carbohydrates account for 60-65% of total calories. The carbohydrates that are normally consumed are mainly polysaccharides, which have a high content in staple foods such as rice and noodles. When carbohydrates are ingested, they can obtain other nutrients such as proteins, lipids, vitamins, minerals, and dietary fiber. The intake of monosaccharides or disaccharides such as sucrose, in addition to supplemental calories, can not add other nutrients.
(2) Constituting cells and tissues: Each cell has carbohydrates, its content is 2% -10%, mainly in the form of glycolipids, glycoproteins and proteoglycans, distributed in the meninges, organelles, cytoplasm and Interstitial cells.
(3) Save protein: The lack of carbohydrates in food, the body has to use protein to meet the energy needed for the body's activities, which will affect the body's use of proteins to synthesize new proteins and tissue renewal. Therefore, it is not appropriate to eat only the meat without eating the staple food. Because the meat contains very few carbohydrates, the body tissue will use protein to produce heat, which is not good for the body. Therefore, the minimum intake of carbohydrates for weight-reducing patients or diabetics should not be less than 150 grams of staple foods.
(4) Maintain the normal function of brain cells: Glucose is an essential nutrient for maintaining the normal function of the brain. When the blood glucose concentration drops, the brain tissue may be damaged due to lack of energy, causing dysfunction, dizziness, palpitations, and Cold sweat or even coma.
(5) Others: The glycoproteins and proteoglycans in carbohydrates have a lubricating effect. In addition it controls the permeability of the meninges. It is also a precursor to synthetic macromolecular substances such as purines, pyrimidines, and cholesterol.
First, the main physiological functions of carbohydrates
1, constitute an important body of the material;
2, provide heat energy;
3, adjust food flavor;
4. Maintain the necessary energy for brain function;
5, regulate fat metabolism;
6, provide dietary fiber;
Second, carbohydrates and health
The lack of carbohydrates in the diet will lead to general weakness, fatigue, lower blood sugar levels, dizziness, heart palpitations, and brain dysfunction. In severe cases, it can cause hypoglycemia.
When there is too much carbohydrate in the diet, it will be converted into fat and stored in the body, making people overweight and leading to various diseases such as high blood lipids, diabetes and so on.
Three, carbohydrate daily recommended amount and its food source
In general, there are no specific dietary requirements for carbohydrates. The main reason is to get a reasonable amount of calorie intake from carbohydrates. In addition, at least 50 to 100 grams of digestible carbohydrates should be consumed daily to prevent carbohydrate deficiencies.
The main food sources of carbohydrates are: sucrose, grains (such as rice, wheat, corn, barley, oats, sorghum, etc.), fruits (such as sugar cane, melon, watermelon, bananas, grapes, etc.), nuts, vegetables (such as carrots, sweet potatoes) and many more.