Choline has been discovered for 150 years. According to Ensminger's writings, Gobley isolated a lecithin (1ecithin) from egg yolk in 1844; Streker isolated a compound from pig bile in 1849 , named "choline" in 1862, Baeyer and Wurtz determined the chemical structure of choline and synthesized choline for the first time. However, for a long period of time, the research on choline did not receive much attention. It was not until 1932 that Best reported for the first time that choline could prevent the occurrence of fatty liver when rats were fed high-fat feed, and proved that choline was the active component of lecithin. After that, research on choline gradually increased. The role of choline in metabolism is multifaceted, including acetylation, phosphorylation, oxidation and hydrolysis. It accelerates the synthesis and release of acetylcholine, an important neurotransmitter, thereby affecting the body's memory, muscle movement and other functions; choline is the precursor of phosphatidylcholine and sphingomyelin, both of which are necessary to form cell membranes. It is also a precursor substance for various signals between cells; choline is also a powerful activator of platelets; choline is the precursor of betaine, and glomerular cells need betaine to regulate osmotic pressure. 2.1 Choline constitutes and maintains normal cell structure. Choline is a component of lecithin and sphingomyelin. In the process of synthesizing the above phospholipids, choline first provides a phosphate group from ATP under the action of choline kinase. It is phosphocholine, which together with CTP generates CTP-choline under the action of phosphocholine cytidylyltransferase. Schneider et al. found that the activity of phosphocholine cytidylyltransferase in rats lacking choline was 40% lower than normal. . CTP-choline further reacts with diglyceride or N-acyl sphingosine, respectively, to finally generate lecithin or sphingomyelin. Lecithin is a component of the animal cell membrane structure, accounting for about half of the transported lipids in the cell plasma membrane; it has also been found that lecithin is necessary to maintain the activity of β-hydroxybutyrate dehydrogenase, and lysolecithin is required to activate Golgi Necessary for the complex or glycosyl transferase on the cell membrane. Lecithin and cholesterol on the normal red blood cell membrane maintain a certain ratio to maintain the flexibility and fluidity of the red blood cell membrane, which is crucial for red blood cells to pass through capillaries. Sphingomyelin is the most abundant sphingomyelin in the human body and an important phospholipid that forms biological membranes. It often coexists with lecithin on the outside of the cell membrane. Nerve myelin contains many lipids, accounting for 97% of the dry weight, of which 11% is lecithin and 5% is sphingomyelin. 20-30% of human red blood cells contain sphingomyelin. 2.2 Choline is an important component of unstable methyl groups in the body. The so-called unstable methyl groups refer to methyl groups that are transferred from one compound to another in the body, also known as active methyl groups. The formation of methionine from homocystine (i.e. homocystine) and the formation of creatine from guanidinoacetyl require the donation of methyl groups. Methylation of many endogenous substrates, such as histamine, amino acids, proteins, sugars, and polyamines, is important for the normal regulation of cells. The direct donor of methyl groups in the transmethylation reaction is S-adenine methionine (SAM), but choline and its related substances methionine, vitamin B12, folic acid, betaine, etc. can indirectly supply methyl groups. In terms of donors, the above substances can supplement or replace each other in most cases, but there are exceptions. Some scholars have found that in total intravenous nutrition, if no choline is added to the injection, even if methionine and folic acid are sufficient, fatty liver will occur. Wait for liver damage. Choline can serve as a methyl donor, but choline synthesis also requires methyl groups. The choline needed by the human body is mainly synthesized through active methyl groups in the body and through dietary supplements. 2.3 Choline is the precursor of neurotransmitters. Choline is the precursor of acetylcholine synthesis. Acetylcholine is the chemical transmitter of neural activity released by parasympathetic nerve terminals, that is, the neurotransmitter of cholinergic nerves. For example, it stimulates the vagus nerve and releases acetylcholine, causing slow heartbeat. The contraction of the fallopian tube is also restricted by the action of acetylcholine. Recent research has found that the combined use of choline and morphine or aspirin can reduce the dosage of analgesics without affecting the analgesic effect, thereby reducing the toxic side effects of morphine or aspirin. This analgesic characteristic of choline can provide a new idea for clinical drug treatment of pain [3].

2.4 Health-care functions of lecithin Lecithin is one of the products of choline that plays important physiological functions. Lecithin is the main component of human cell membranes. Lecithin is present in the cells of various organs and tissues in our body, and the content of lecithin is particularly high in tissues such as the brain and liver. There are approximately 200 ml lecithin per 100 ml blood. All in all, the human lecithin content accounts for about one percent of body weight. Some people believe that "lecithin is the basic substance of life" and is currently the most popular "brain-building health food" in the United States and Japan. Now, most scholars believe that lecithin has four major functions: (1) enhances cell activity; (2) dissolves cholesterol; (3) improves brain function and prevents Alzheimer's disease; (4) synergizes with vitamin E. Human life is inseparable from lecithin from beginning to end. A small amount of lecithin required for life can be synthesized and secreted by the liver, but after the age of 30, it can basically only be taken from food. Egg yolks, soybeans, cereals, small fish, animal livers, eels, corn oil, and sunflower oil all contain a certain amount of lecithin