Trimethylglycine (TMG), also known as betaine, is scientifically studied for its role in supporting the hepatic (liver) system. TMG acts as a methyl donor in the body, particularly in the process of homocysteine metabolism. The liver is a central organ in methylation reactions, and elevated homocysteine is a risk factor for liver dysfunction, among other health issues. TMG facilitates the conversion of homocysteine to methionine via the enzyme betaine-homocysteine methyltransferase, which is highly expressed in the liver.

Several animal and human studies suggest that TMG supplementation may help protect the liver from damage caused by toxins, alcohol, and fatty liver disease (hepatic steatosis). For example, clinical trials and preclinical studies have shown that TMG can reduce liver fat accumulation and improve markers of liver health in people with non-alcoholic fatty liver disease (NAFLD). A review published in Liver International (2013) and research in World Journal of Gastroenterology (2015) both highlight TMG's hepatoprotective effects, though results are sometimes mixed and not all trials show significant benefit.

While TMG is not a first-line treatment for liver disease, and more large-scale, long-term studies are needed, the current body of scientific literature supports its role in liver methylation processes and suggests potential benefits for liver health, particularly in the context of fatty liver and elevated homocysteine.