The Primary Identity: Trimethylglycine (TMG)
While the term 'betaine' is used broadly, it most frequently refers to trimethylglycine (TMG), an amino acid derivative composed of the amino acid glycine with three methyl groups attached. It's a zwitterion, meaning it has both positive and negative charges, which is key to its role as an osmolyte. Betaine was given its name after being first discovered in sugar beets (Beta vulgaris), and it is also referred to as glycine betaine. The anhydrous form is the pure, water-free version often used in supplements.
Betaine’s Core Functions in the Body
Betaine performs two primary functions crucial for cellular and metabolic health:
- Methyl Donor: Betaine is a key methyl-group donor, meaning it provides methyl groups ($CH_3$) for vital biochemical reactions. Its most significant role in this capacity is converting the amino acid homocysteine back into methionine. High levels of homocysteine are associated with an increased risk of cardiovascular disease, so betaine helps regulate this amino acid in the blood. This methylation process is also essential for DNA production, neurotransmitter synthesis, and other fundamental bodily processes.
- Osmolyte: As an osmolyte, betaine helps cells maintain their hydration and volume, particularly under stress from heat or high salinity. It protects cellular components, including proteins and enzymes, from damage caused by changes in osmotic pressure. This function is especially important in the kidneys, where betaine helps protect cells from high electrolyte concentrations. This osmoregulatory effect is also a factor in its potential benefits for athletic performance.
Natural Sources of Betaine
Betaine is found naturally in many foods, with some of the highest concentrations occurring in certain plant-based foods and seafood. Some of the most potent food sources include:
- Wheat Bran
- Wheat Germ
- Spinach
- Beets
- Quinoa
- Shrimp and Shellfish
Important Distinction: Betaine vs. Betaine Hydrochloride (Betaine HCl)
It is crucial not to confuse betaine anhydrous (TMG) with betaine hydrochloride (betaine HCl). Despite the similar names, they have entirely different uses and effects.
| Feature | Betaine (Trimethylglycine/Anhydrous) | Betaine Hydrochloride (Betaine HCl) |
|---|---|---|
| Primary Function | Methyl donor and osmolyte | Digestive aid for low stomach acid (Hypochlorhydria) |
| Mechanism | Donates methyl groups to convert homocysteine to methionine | Provides a source of hydrochloric acid (HCl) to supplement stomach acid |
| Regulation | FDA-approved as Cystadane for homocystinuria; available as dietary supplement | Previously marketed OTC for gastric aid, but FDA has not recognized as safe/effective for that use |
| Primary Use | Lowering homocysteine, athletic performance, liver health | Improve digestion and nutrient absorption in individuals with low stomach acid |
Other Contexts and Trade Names
Beyond its chemical name, betaine can appear under different contexts or trade names. For example, the prescription drug Cystadane, used for treating homocystinuria, is a specific form of betaine anhydrous. This highlights its important therapeutic use for a rare genetic disorder where the body cannot properly metabolize homocysteine. The European Medicines Agency (EMA) also approves products like Amversio for the same purpose.
Furthermore, in the context of supplements, betaine may be listed simply as TMG. The term 'betaine' itself is a chemical class of molecules, and TMG was simply the first one discovered from beets, which is why it holds the generic name. Another metabolite, dimethylglycine (DMG), is often confused with TMG, but DMG is a demethylated version of betaine and is not a methylating agent itself.
Conclusion
While the simple name 'betaine' is widely used, it is more precisely defined as trimethylglycine (TMG), also known as glycine betaine. This compound’s dual function as a methyl donor and cellular osmolyte is fundamental to its health benefits, including regulating homocysteine levels and protecting against cellular stress. By understanding what betaine is also known as and distinguishing it from related compounds like betaine HCl, consumers can make more informed choices about their nutritional and supplemental intake. Whether sourced from foods like spinach and whole grains or taken as an anhydrous supplement, TMG is a valuable compound in human metabolism. For comprehensive information on metabolic pathways, consulting an authoritative source like the National Institutes of Health (NIH) is recommended. Read more on betaine research from the NIH.
