Choline is the parent compound of choline compounds, with a structure in which the amino group of ethanolamine is substituted by three methyl groups. Choline acts as a neurotransmitter, nutrient, and allergen, and is an endogenous metabolite in mice, Saccharomyces cerevisiae, plants, Escherichia coli, humans, and Daphnia magna. Choline is involved in the regulation of gallbladder function, hepatic physiology, and the synthesis of the key lipid lecithin; it promotes fat and cholesterol metabolism, reduces excessive fat accumulation in the liver, and can also be used to alleviate symptoms associated with Parkinsonism and tardive dyskinesia. Choline deficiency may cause abnormal hepatic fat deposition, hypertension, gastric ulcers, liver and kidney damage, growth retardation, and other disorders.