Trimethylglycine (Betaine) Trimethylglycine functions very closely with choline, folic acid, vitamin B12, and a form of the amino acid methionine known as S-adenosylmethionine (SAMe). All of these compounds function as "methyl donors." They carry and donate methyl molecules to facilitate necessary chemical processes. The donation of methyl groups is very important to proper liver function, cellular replication, and detoxification reactions. Betaine also plays a role in the manufacture of carnitine and serves to protect the kidneys from damage. Betaine is closely related to choline. The difference is that choline (tetramethylglycine) has four methyl groups attached to it. When choline donates one of these groups to another molecule, it becomes betaine (trimethylglycine). If betaine donates one of its methyl groups, then it becomes dimethylglycine.