Choline is a widely used and indispensable biological agent. Many metabolic processes take place only with the cooperation of choline. Therefore, choline deficiency leads to a variety of health problems.
What is choline?
Choline is a quaternary ammonium compound, which is also a monohydric alcohol. Here, the nitrogen atom is surrounded by three methyl groups and one hydroxyl group. Since the ammonium compound is positively charged, it exists as a salt. It is commercially available as choline chloride. The active ingredient is found in many foods as a water-soluble semiessential nutrient. It was first discovered in pig bile by the German chemist Adolph Strecker in 1849. In 1862, Adolph Strecker characterized and named this active ingredient. Earlier, choline was classified as a vitamin of the vitamin B complex, as it showed a characteristic effect on the nervous system and various metabolic processes when ingested. However, it was also recognized that it is also produced in human metabolism from the amino acids methionine and lysine. However, the body’s own production is not so high that the choline requirement can be adequately met at all times. For this reason, choline is now referred to as a vitamin-like substance. Choline takes its name from the Greek word for bile, “cholé”. As an important component of bile, it is responsible for the emulsification of fat-like substances and thus for the removal of fat from the liver.
Function, effects and tasks
Choline has multiple functions in the human organism. Among other things, it is converted in the body into acetylcholine by esterification with acetic acid. Acetylcholine is an important neurotransmitter responsible for the transmission of nerve impulses. It plays a major role in both the sympathetic and parasympathetic nervous systems. This transmission of impulses has a significant influence on thinking performance, concentration and memory in humans. Thus, at low choline concentrations, significantly reduced concentration and memory performance have been observed. Furthermore, choline is also involved in the synthesis of myelin. Myelin is a protein substance that protects the nerve tracts from external influences by insulating them. Choline is also an essential component of cell membranes in the form of phospholipids. The best known phospholipid of membranes is lecithin. Lecithin consists of glycerol esterified with two fatty acids and choline. Cell contacts are also mediated via the membrane phospholipids of choline. Choline, along with folic acid and methionine, is also an important methyl group transmitter. In the case of folic acid and vitamin B12 deficiency, choline ensures the methylation of homocysteine into methionine. In this way, it helps to ensure that methionine can continue to function as a methyl group transmitter. Choline also performs an important task in the bile. There, in its esterified form, it ensures the emulsification of lipids and can thus transport fat and cholesterol out of the liver. This prevents the accumulation of fat in the liver. Finally, choline is also involved in the synthesis of important hormones such as norepinephrine and melatonin.
Formation, occurrence, properties, and optimal values
Choline is widely distributed in nature. In the human organism, it is produced from the amino acids lysine and methionine. When biodegraded, lysine yields the metabolite dimethylamine, which is methylated to choline by the methyl group donor methionine. In the body, it is present esterified as lecithin in cell membranes, as a metabolite in metabolism, and esterified with acetic acid as the neurotransmitter acetylcholine. Since it is bound as lecithin in the cell membranes of all living organisms, it can be supplied very easily through food. Thus, it is present in foods that still have cell membrane components. Particularly high amounts of choline are found in egg yolks, beef liver, chicken liver, wheat germ, bacon, dried soybeans or pork. A healthy and varied diet should cover the daily choline requirement. In a vegetarian diet, special care should be taken to consume choline-rich vegetables. These include grains and legumes.
Diseases and disorders
Since choline plays a central role in many processes in the organism, a choline deficiency has a negative effect on the state of health.There is normally enough choline in the diet, so that a choline deficiency should not actually occur. Nevertheless, there are diseases that can be traced back to a choline deficiency. Excessive alcohol consumption can lead to choline deficiency. A fat malabsorption disorder also leads to this. Furthermore, a deficiency of folic acid also leads to a secondary choline deficiency. If folic acid is lacking, choline takes over the function of the methyl group transmitter. In the process, it is degraded and is no longer available for other processes. The body’s own synthesis is not sufficient. Severe diseases such as AIDS can also lead to a choline deficiency. The consequences of an undersupply of choline are manifold. The most drastic is the development of a fatty liver. Due to the lack of choline, fats can no longer be transported out of the liver. They are stored in the hepatocytes. As a result, the liver can no longer perform its detoxification function properly. In the long term, liver breakdown occurs. In deficiency states, choline is also no longer sufficiently available for the synthesis of acetylcholine. Symptoms such as concentration disorders and forgetfulness occur. Low choline levels are often also associated with elevated homocysteine levels in the blood. Homocysteine is considered a risk factor for the development of arteriosclerosis. Furthermore, a choline deficiency also appears to worsen the pathogenesis of some diseases. It has been found, for example, that ulcerative colitis is positively influenced by the administration of lecithin. The same is true for chronic inflammation or even breast cancer.
