Carbohydrates can be divided into three types: monosaccharides, oligosaccharides and polysaccharides.

 1. Sugar

 Monosaccharides are the simplest sugar in structure, under usual terms, they can no longer be broken into smalller sugar monomers. Mainly of them are glucose, D-galactose, D-fructose.

 Disaccharides are the molecules which are produced by dehydration of the hydroxyl groups on two identical different monosaccharide molecules.

 The most common disaccharides in nature are sucroses and lactose,what’s more ,there are also

maltose, trehalose, isomaltose, cellobiose, chitobiose, etc.

 Sugar alcohol is an important derivative of monosaccharides, common ones are sorbitol, mannitol, xylitol, maltitol and so on.

 Oligosaccharides are also called oligosaccharides.  Several currently konwn important oligosaccharides include raffinose, stachyose, isomalto-oligosaccharides, fructooligosaccharides, mannose oligosaccharides, soybean oligosaccharides and so on.  Its sweetness is usually only 30% to 60% of sucrose.

 Polysaccharides are generally insoluble in water, have no sweet taste, do not form crystals, and have no reducing properties. Under the action of enzymes or acids, it is hydrolyzed into fragments with different residues of monosaccharides, and finally becomes monosaccharides. Including starch, glycogen and dietary fiber.

 2. The physiological functions of carbohydrates.

 ①. Supply and store energy

 Dietary carbohydrates are the most economical and main source of energy for our human beings. Among the energy needed to maintain human health, 55%-65% are provided by carbohydrates.  Carbohydrates release energy quickly in the body and supply energy quickly. They are the main energy source for the nervous system and myocardium, as well as the main fuel for muscle activity. They are of great significance to maintain the normal energy supply of the nervous system and the heart, enhance endurance, and improve work efficiency.

 ②. Constituent organization and vital life matter.

 Carbohydrates are important substances that constitute body tissues and participate in the composition and various activities of cells. Each cell has carbohydrates, the content of which is about 2% to 10%, mainly in the form of glycolipids, glycoproteins and proteoglycans. Some substances with important physiological functions, such as components of antibodies, enzymes and hormones, also require carbohydrates.

 ③. Saving protein

 When enough carbohydrates are taken in, it can prevent the consumption of protein in the body or diet, and there is no need to use protein for energy, therefore, carbohydrates can save protein.

 ④. Detoxification

 Glucuronic acid produced by the uronic acid is an important binding antidote in the body. It can be combined with many harmful substances such as bacterial toxins, alcohol, arsenic, etc. in the liver to eliminate or reduce the toxicity or biological activity of these substances, thus it’s playing a detoxification effect.

 ⑤. Non-starch polysaccharides such as cellulose and pectin, resistant starch, functional oligosaccharides and other anti-digestible carbohydrates can stimulate intestinal peristalsis, increase fermentation in the colon, short-chain fatty acids and intestinal bacteria produced by fermentation group proliferation, helps normal digestion and increases bowel movements.

   3. Carbohydrate intake

 (1). Insufficient intake

 ①. Decline of memory

 Insufficient intake of carbohydrate food may reduce the supply of glucose required by brain cells, thus causing damage to learning, memory and thinking.

 ②. Affect human physiological functions

 Long-term lack of staple foods in the diet can also lead to lower blood sugar levels, causing dizziness, heart palpitations, brain dysfunction, and other problems. In severe cases, it can lead to hypoglycemic coma.

③. Cause human illness

 Carbohydrates are an essential factor for maintaining a healthy body. Long-term inadequate intake can lead to metabolic disorders, kidney stones, osteoporosis and other diseases.

 ④. Affect growth and development

 Carbohydrates are the main source of human energy. Long-term lack of energy can lead to malnutrition and growth retardation.

 (2). Excessive intake

 ①. Cause obesity

 Excessive carbohydrate intake will convert the unusable glucose after decomposition into fat, thereby causing obesity.

 ②. Cause diabetes

 Excessive carbohydrate intake will increase the body's blood sugar concentration. Long-term excess will cause damage to the pancreas, and ultimately cause insufficient insulin secretion and cause diabetes.

 4. Food sources of carbohydrates

 The main source of starch in the diet is grains and tubers.  Cereals generally contain 60% to 80% carbohydrates, 15% to 29% in potatoes, and 40% to 60% in beans.  The main sources of monosaccharides and disaccharides are sucrose, candies, sweets, pastries, sweet fruits, sugary drinks and honey.

 5. Conclusions

 With the improvement of the current living standards, people have higher and higher dietary requirements. High carbohydrates and high energy can lead to obesity, high blood sugar and other diseases. Therefore, modern people begin to require low-sugar diets. The carbohydrate content of young barley seedling powder can be said to be basically no. It is a low-sugar food, avoiding the intake of high energy and high sugar, and its low-sugar feature is becoming more and more popular among people.