Trimethylglycine or TMG for short is a substance that occurs naturally in the body. It plays a part in many processes such as cellular reproduction, liver functioning and the creation of carnitine. It also helps the body in metabolizing homocysteine, an amino acid. TMG has been studied for a plethora of health benefits such as enhancing heart health, promoting healthy insulin levels, boosting athletic performance and protecting against depression. Although well tolerated, some side effects may include diarrhea, body odor, stomach upset and nausea.