The main physiological functions of vitamin B12

Firstly, it improves the utilization rate of folic acid and synthesizes methionine (synthesized from homocysteine) and choline together with folic acid to produce purine In the process of synthesizing cyanocobalamin and pyrimidine, precursor substances such as methylcobalamin and coenzyme B12 are involved in the methylation process of many important compounds. When vitamin B12 is deficient, the activity of transferring methyl groups from methyltetrahydrofolate is reduced, causing folic acid to become an unusable form, leading to folate deficiency.

The second is to maintain the metabolism and function of nerve myelin. Lack of vitamin B12 can cause neurological disorders, spinal cord degeneration, and severe mental symptoms. Vitamin B12 deficiency can lead to peripheral neuritis. The early manifestations of vitamin B12 deficiency in children are abnormal mood, dull expression, slow reaction, and eventually anemia.

The third is to promote the development and maturation of red blood cells. Converts methylmalonyl-CoA into succinyl-CoA and participates in the tricarboxylic acid cycle, where succinyl-CoA is related to the synthesis of heme.

Fourth, vitamin B12 is also involved in the synthesis of deoxynucleic acid (DNA), the metabolism of fat, carbohydrates and proteins, and increases the synthesis of nucleic acids and proteins.

The main food source of vitamin B12

Humans cannot synthesize vitamin B12 themselves, so they need to obtain it from the diet. Vitamin B12 in the diet mainly comes from animal foods, especially animal offal (content can be as high as 10μg/100g, wet weight), fish and eggs, followed by dairy (about 1μg/100g); plant foods Food generally does not contain this vitamin, but my country's soy fermented foods and kimchi contain a certain amount; in addition, if the plants are contaminated by bacteria or grow with them, trace amounts may be present. Some microorganisms in the human colon can also synthesize vitamin B12, but they are often bound to protein and are not easily absorbed.

Causes and symptoms of vitamin B12 deficiency

The main causes of vitamin B12 deficiency are: insufficient intake, such as long-term vegetarians; acquired malabsorption, such as pancreatic origin and gastric origin. Sexual, liver-derived or intestinal-derived diseases, etc.; increased demand for vitamin B12, such as pregnancy, postpartum, taeniasis, etc.; congenital disorders of vitamin B12 metabolism steps, such as congenital lack of intrinsic factor, etc. [3].

The deficiency of vitamin B12 is mainly reflected in the blood and nervous system, which can lead to pernicious anemia, Alzheimer's disease, mental depression and other diseases.

4.1 Pernicious anemia

Methyl vitamin B12 and 5′-deoxyadenosine vitamin B12 are the metabolically activated forms of vitamin B12 in human cells. They serve as methylmalonyl coenzymes Coenzymes of A mutase, L-α-leucine mutase and methionine synthase play an important role in the metabolism of humans and other mammals. Vitamin B12 deficiency will lead to reduced DNA synthesis, reduced mitosis rate, delay or even destroy the differentiation of normal cells, especially bone marrow cells and mucosal cells, and form abnormal giant cells. This phenomenon is called "megaloblast transformation". It is a typical feature of pernicious anemia (also known as megaloblastic anemia) [4].

In human tissues, vitamin B12 is related to the synthesis of heme. When vitamin B12 is lacking, it affects the normal progress of its biochemical reactions, heme synthesis is hindered, and the survival time of red blood cells is moderately shortened. Although megaloblastic cells increase at all stages in the skeleton, compensation does not occur, and anemia occurs.

4.2 Alzheimer's disease

Vitamin B12 deficiency also causes diffuse and progressive nerve demyelination, destroys the normal shape and function of nerve cells, and induces various neurological diseases. This disease often starts in the peripheral nerves and gradually develops into the posterior and lateral segments of the spinal cord, causing abnormal sensation, memory loss and even Alzheimer's disease [5].

The coenzyme of vitamin B12 has the role of a coenzyme of methionine synthase, which can transfer methyl groups from 5′-methyltetrahydrofolate, enhance the metabolism of folic acid, and thereby reduce homocysteine ??(a) in the body. A potentially harmful amino acid, produced by the reaction of methionine) content.

Studies have found that as the homocysteine ??content in the blood increases, the incidence of heart disease and other vascular diseases will also increase. Therefore, insufficient intake of vitamin B12 in the body will lead to reduced mental acuity, and trace deficiency can cause depression and depression. Panic, severe deficiency can easily lead to fatigue, neurasthenia and Alzheimer's disease [4].

4.3 Depression

Vitamin B12 participates in the synthesis of nucleic acids, promotes the development and maturation of red blood cells, ensures the oxygen supply of cranial nerve cells, and can maintain the myelin sheath of nerves around the central nervous system. Normal metabolism, maintains the integrity of nerve fibers, participates in a variety of metabolic processes, and maintains brain nerve media in a normal state. Therefore, vitamin B12 deficiency can easily cause slow thinking, depression, loss of will, and suicidal thoughts and behaviors. The survey found that 1/4 of patients with depression are deficient in vitamin B12