Vitamin B 12 in nature is mainly synthesized by bacteria in rumen and colon of herbivores, so its dietary source is mainly animal food, among which animal viscera, meat and eggs are rich sources of vitamin B 12. Soybean products will produce a part of vitamin B 12 after fermentation. Human intestinal bacteria can also synthesize some.
Extended data:
Vitamins are an organic compound necessary to maintain health. This kind of substance is neither the raw material of body tissue nor the source of energy in the body, but a kind of regulating substance, which plays an important role in substance metabolism. Because these substances cannot be synthesized in the body or the amount of synthesis is insufficient, although the amount needed is small, it always depends on food supply. ?
Vitamins, also known as vitamins, are life-sustaining substances, organic substances necessary to maintain human life activities and important active substances to maintain human health. The content of vitamins in the body is very small, but it is indispensable. Although the chemical structures and properties of various vitamins are different, they have the following similarities:
① Vitamins exist in food in the form of provitamins;
Vitamins are not components of tissues and cells, do not produce energy, and mainly participate in the regulation of metabolism;
(3) Most vitamins can't be synthesized by the body or the synthetic amount is not enough to meet the needs of the body, so they must be obtained from food frequently;
(4) The human body's demand for vitamins is very small, and the daily demand is often calculated in milligrams or micrograms, but once it is lacking, it will cause the corresponding vitamin deficiency and cause harm to human health;
Vitamins, unlike carbohydrates, fats and protein, account for only a small proportion in natural foods, but they are also necessary for human body. Some vitamins, such as B6. K can be synthesized by bacteria in animal intestines, and the synthetic amount can meet the needs of animals.
Animal cells can convert tryptophan into nicotinic acid (a B vitamin), but the yield is not enough. Vitamin C can be synthesized by animals other than primates and guinea pigs. Plants and most microorganisms can synthesize vitamins by themselves without external supply. Many vitamins are components of helper groups or coenzymes.
Vitamins are some trace organic compounds necessary for human and animal nutrition and growth, and play an extremely important role in the metabolism, growth, development and health of the body. If a vitamin is lacking for a long time, it will cause physiological dysfunction and some diseases. Generally obtained from food. There are dozens of species found at this stage, such as vitamin A, vitamin B, vitamin C and so on.
Vitamins are essential organic compounds in human metabolism. The human body is like an extremely complex chemical plant, constantly carrying out various biochemical reactions. This reaction is closely related to the catalysis of enzyme. Coenzymes must participate in the activities of enzymes. It is known that many vitamins are coenzymes of enzymes or constituent molecules of coenzymes. Therefore, vitamins are important substances to maintain and regulate the normal metabolism of the body. It can be considered that the best vitamins exist in human tissues in the form of "bioactive substances".
Lack of rationality
1, the food supply is seriously insufficient and the intake is insufficient; Such as: single food, improper storage, cooking damage, etc. For example, folic acid is lost by heat.
2. Reduce absorption and utilization; For example, digestive system diseases or low fat intake affect the absorption of fat-soluble Vit.
3. The demand for vitamins is relatively high; Such as: pregnant women, lactating women, children, special posts, special environmental groups.
4. The unreasonable use of antibiotics will lead to the increase of vitamin demand. ?
Essential vitamins
The definition of vitamins requires that vitamins meet the following four characteristics before they can be called essential vitamins.
Exogenous: the human body cannot synthesize itself and needs food supplement;
Traces: the human body needs little, but it can play a huge role;
Regulatory: vitamins must be able to regulate human metabolism or energy conversion;
Specificity: Without certain vitamins, people will show a unique pathological state.
According to these four characteristics, the human body needs 13 vitamins, which is also commonly known as 13 essential vitamins:
Vitamin a, vitamin b, vitamin c, vitamin d, vitamin h, vitamin p, vitamin PP, vitamin m, vitamin t, vitamin u, water-soluble vitamin.
rise
The discovery of vitamins is one of the great discoveries of19th century. 1897, Aikman discovered that eating only ground white rice in Java Island may cause beriberi, and unpolished brown rice can treat the disease. It was also found that substances that can cure beriberi can be extracted with water or alcohol, which was called "water-soluble B" at that time. 1906 proves that food contains "auxiliary factors" other than protein, lipids, carbohydrates, inorganic salts and water, which are extremely small substances necessary for animal growth.
19 1 1 year, kazimierz funk identified that the substances that can fight beriberi in brown rice are amines, which are similar in nature and distribution in food, and most of them are coenzymes. Some supplies must be balanced with each other, such as vitamin B 1, B2 and PP, otherwise physiological functions may be affected. Vitamin B complex includes pantothenic acid, nicotinic acid, biotin, folic acid, vitamin B 1 (thiamine), vitamin B2 (riboflavin), pyridoxine (vitamin B6) and cyanocobalamin (vitamin B 12). Some people also add choline, inositol, p-aminobenzoic acid (p-aminobenzoic acid), carnitine and lipoic acid to the B complex.
Sources of various vitamins:
Vitamin A is an anti-dry eye vitamin, also known as cosmetic vitamin, which is fat-soluble. It was discovered by Elmer mccollum and M Davies between 19 12 and 19 14. It is not a single compound, but a series of derivatives of retinol (retinol is also translated into vitamin A alcohol, rosin oil). Another name for anti-dry eye vitamins mainly exists in cod liver oil, animal liver and green vegetables. Lack of vitamin A is prone to night blindness.
Vitamin B 1 and thiamine, also known as anti-beriberi factor and anti-neuritis factor, are water-soluble vitamins. By casimir? It was discovered by Feng Ke in 19 12 (for example 19 1 1). It usually exists in organisms in the form of thiamine pyrophosphate. Most of them are found in yeast, grains, liver, soybeans and meat.
Vitamin B2, riboflavin, water solubility. Discovered by D.T. Smith and E. Hendrick in 1926. Also known as vitamin G, it exists in yeast, liver, vegetables and eggs. Lack of vitamin B2 is prone to oral inflammation (oral ulcer) and so on.
Water-soluble vitamin PP Conrad Elvehjem discovered it in 1937. Including nicotinic acid (nicotinic acid) and nicotinamide (nicotinamide), all belong to pyridine derivatives. Most of them are found in nicotinic acid, nicotinic acid yeast, grain, liver and rice bran.
Vitamin B4 is no longer regarded as a real vitamin at this stage. Choline was discovered by Maurice Gobley in 1850. Choline, one of the B vitamins, was first isolated from pig liver in 1849. Since then, choline has been considered as a component of phospholipids. Sura and Gyorg goldblatt, according to their respective work, showed that it has the characteristics of vitamins. The content of lecithin in eggs, animal brains, beer yeast, malt and soybean is high.
Calcium pantothenate, pantothenic acid, water solubility. Discovered by roger williams in 1933. Also known as pantothenic acid. Most of them are found in yeast, grains, liver and vegetables.
Vitamin B6, pyridoxine, water solubility. /kloc-0 was discovered by Paul Gyorg in 934. Include pyridoxine, pyridoxal and pyridoxamine. Most of them are found in yeast, grain, liver, eggs and dairy products.
Biotin, also known as vitamin H or coenzyme R, is water-soluble. Most of them are found in yeast, liver and grains.
Vitamin B9? Folic acid, water soluble. Also known as pteroyl glutamic acid, pteroyl glutamic acid, vitamin M or leaf essence. Most of them are found in vegetable leaves and liver.
Vitamin B 12, cyanocobalamin, water-soluble. Discovered by Karl Fox and Alexander Todd in 1948. Also known as cyanocobalamin or coenzyme B 12. Most of them are found in liver, fish, meat and eggs.
Inositol, water solubility, cyclohexanol, vitamin B-H. Mainly in the heart and meat.
Vitamin c, ascorbic acid, water solubility. By James? Linde found it in 1747. Also known as ascorbic acid. Most of them exist in fresh vegetables and fruits.
Vitamin d, calciferol, fat solubility. Discovered by Edward Melanby in 1922. Also known as calciferol and anti-rickets vitamins, there are mainly vitamin D2, ergocalciferol and vitamin D3, and cholecalciferol. This is the only vitamin that the human body can synthesize in small quantities. Most of them are found in cod liver oil, egg yolk, dairy products and yeast.
Vitamin e and tocopherol are fat-soluble. It was discovered by Herbert Evans and Catherine Bishop in 1922. There are mainly four kinds: α, β, γ and δ. Most of them are found in eggs, liver, fish and vegetable oil.
Vitamin k, naphthoquinone, fat-soluble. It was discovered by Henrik Dam in 1929. It is the floorboard of a series of naphthoquinone derivatives, mainly including natural vitamin K 1 from plants, vitamin K2 from animals, and synthetic vitamins K3 and K4. Also known as clotting vitamins. Most of them are found in spinach, alfalfa, cabbage and liver.
References:
Vitamin B 12_ Baidu Encyclopedia Vitamin _ Baidu Encyclopedia