Betaine, metabolic by-product or vital methylating agent?

The possible physiological role of betaine, the oxidative product of choline, is considered. It is proposed that betaine, instead of merely being a metabolic by-product of choline oxidation, may serve as an important methylating agent when normal methylating pathways are impaired by ethanol ingestion, drugs or nutritional imbalances. Furthermore, betaine may prove to have therapeutic application in cases of altered folate, vitamin B12 or methionine metabolism.