1, water
For the human body, water is an important component, accounting for 40-60% of the body mass, and exists in urine, blood, digestive juice and extracellular fluid in large quantities.
Function: Water is an indispensable substance for human body and participates in all metabolic activities in the body. Carbohydrates, fats and protein all produce water in metabolism.
2. protein
The basic building block of protein is amino acids, which are macromolecules linked by peptide bonds, forming a certain spatial structure. Due to the variety, quantity, arrangement order and spatial structure of amino acids in protein, there are countless protein with different functions.
Protein is the material basis of all life. Without protein, there would be no life. In normal adults, the content of protein is 16%-20%, and a 70kg healthy adult male contains about11.2-14.0kg. Protein in human body is in a dynamic balance of continuous decomposition and synthesis, thus achieving the purpose of continuous renewal and repair of tissue protein. Protein in intestine and bone marrow is updated rapidly.
Function: protein is the embodiment of life activities and the richest organic matter in life. Protein accounts for about 1/5 of human body weight, and it is the most important life substance. There are many kinds in protein. It is conservatively estimated that there are more than100000 kinds of protein in human body, and different protein have different functions.
Protein is the main component of human tissues, cells and body fluids, and also the main component of enzymes, hormones and antibodies, followed by energy supply, accounting for 8%- 15% of the total energy. The most important function is to maintain the renewal, growth and repair of human tissues.
3. Lipids
Lipids, including fats and lipids, are a kind of compounds insoluble in water but soluble in organic solvents. The main component of fat is fatty acid. Fatty acids that cannot be synthesized by human body and must be supplied by food are called essential fatty acids. Such as n-6 series of dumb oleic acid (LA) and n-3 series of linolenic acid (LNA), linoleic acid can be derived from various n-6 unsaturated fatty acids, such as arachidonic acid.
Linoleic acid can be converted into linolenic acid and arachidonic acid in the body, so linoleic acid is the most important essential fatty acid. Linolenic acid can also be derived from a variety of n-3 unsaturated fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
Function:
Lipids are important substances for storing and supplying energy. 20%-30% of the daily energy required by human body is supplied by lipids, and each gram of fat can release 37.7 kilojoules of energy when it is completely oxidized and decomposed in the body. When sugar is insufficient, the main energy in the body comes from lipids.
Lipids are an important part of human cells and tissues. Not only the brain nerve, kidney, plasma and other tissues of human body contain a lot of lipids, but also phospholipids, glycolipids, cholesterol and other lipids are bound to participate in the formation of biofilm. In addition, the absorption of some vitamins depends on lipids.
Lipids can be converted into many important metabolites. Lipid catabolism can provide essential fatty acids for life activities; Cholesterol can be converted into bile acids, vitamin D and steroid hormones.
4. carbohydrates
Carbohydrate has always been defined as a kind of compound with the molecular formula of Cn(H2O)n, that is, the molar ratio of C: H: O is 1: 2: 1. This definition excludes sugar alcohols, oligosaccharides and polysaccharides. According to the recommendation of FAO/ WHO expert group (1998), carbohydrates are divided into three groups according to their polymerization degree (that is, the number of monomers): sugar, oligosaccharide and polysaccharide.
The main function of carbohydrate is to provide energy for human body, which is the cheapest nutrient among the three major nutrients and the main source of human energy.
Function: Besides providing energy, carbohydrates have some other special physiological activities. For example, heparin can anticoagulate, participate in the composition of DNA and RNA, and also determine the ABO blood type of human body. In addition, the recognition of foreign invaders by human immune cells is also related to sugar.
5, vitamins
Vitamins are essential nutrients to maintain normal human life activities. According to its characteristics, it can be divided into fat-soluble vitamins and water-soluble vitamins, in which fat-soluble vitamins include vitamin A, vitamin D, vitamin E and vitamin K, while water-soluble vitamins include vitamin B (vitamin B 1, vitamin B2, vitamin PP, vitamin B6, vitamin B 12, folic acid) and vitamin C.
Function: The main function of water-soluble vitamins is to act as coenzyme of enzymes (substances necessary for enzyme activity). Fat-soluble vitamins are not used as coenzyme of enzymes, but participate in other important body functions. Vitamins are the basic elements of human health. Once vitamins are lacking, corresponding diseases will occur.
6. minerals
Minerals Elements other than carbon, hydrogen, oxygen and nitrogen in the human body are called minerals, including inorganic salts and trace elements. They do not provide energy by themselves, but mainly play an important role in composing human substances and regulating physiological and biochemical functions in the body.
Function:
Essential trace elements have very important physiological functions and are essential active factors for enzymes and vitamins. Constitute or participate in the role of hormones; Participate in nucleic acid metabolism.
P and Ca in the body will form hydroxyapatite to form bones, which is the backbone of the human body. Free calcium exists in extracellular fluid and blood to maintain the excited state of skeletal muscle and myocardium, which is needed in daily life.
7. Edible fiber
For dietary fiber, it is mainly divided into insoluble cellulose and water-soluble cellulose. It includes polysaccharide, seaweed, gum, pectin and cellulose. There are chitin, resistant oligosaccharides, resistant starch and lignin in plant cell walls, which exist in staple food and potatoes.
Function: Dietary fiber does not participate in energy supply, but plays an important physiological role in human body. It can reduce serum cholesterol and blood lipid, prevent gallstones and protect cardiovascular system; Can reduce the increase of postprandial blood sugar; Can prevent colon cancer; Conducive to defecation; It can also prevent obesity.
Too little dietary fiber intake will affect intestinal peristalsis, cause constipation and even increase cholesterol.
Baidu encyclopedia-nutrients