Betaine, also known as trimethylglycine (TMG), is a compound naturally present in the human body and various foods. It is a derivative of the amino acid glycine that contains three methyl groups. Betaine is considered a non-essential nutrient because the body can produce it, primarily through the oxidation of choline. Its importance in human health stems from its unique dual function, operating both as a methyl donor and as an osmolyte.
Role as a Methyl Donor and Homocysteine Regulator
Betaine’s primary metabolic function involves donating one of its three methyl groups in a process called remethylation. This action makes it an important component of the one-carbon metabolism cycle in the liver and kidneys. Betaine’s role as a methyl donor is specifically employed in converting the amino acid homocysteine back into methionine.
The enzyme betaine-homocysteine methyltransferase (BHMT) facilitates this reaction. BHMT transfers a methyl group from betaine to homocysteine, creating methionine and converting betaine into dimethylglycine. Methionine is then used to produce S-adenosylmethionine (SAMe), a universal methyl donor for numerous other biochemical reactions. This pathway provides an alternative to the folate-dependent remethylation pathway, helping maintain healthy methionine levels even when other B-vitamins are not fully available.
This remethylation pathway is a crucial mechanism for detoxifying homocysteine, a naturally occurring intermediate in metabolism. Elevated levels of homocysteine in the blood, known as hyperhomocysteinemia, are associated with an increased risk of cardiovascular issues. High homocysteine is thought to damage the lining of blood vessels and interfere with blood clotting factors.
Betaine supplementation can help lower plasma homocysteine concentrations by efficiently converting it back to methionine. This effect is particularly relevant in patients with genetic disorders, such as homocystinuria. Betaine anhydrous is an FDA-approved treatment to manage dangerously high homocysteine levels in these patients. In the general population, betaine’s capacity to regulate this amino acid contributes to overall vascular health.
Use in Enhancing Athletic Performance
Betaine also acts as an osmolyte, a compound that helps maintain cell volume and fluid balance. As an osmolyte, betaine accumulates within muscle cells and draws water into the cell, protecting them from osmotic stress during intense exercise. This function forms the basis for its use as an ergogenic aid, or performance enhancer.
The resulting cellular hydration and swelling can promote a more favorable environment for muscle contraction and protein synthesis. Increased muscle cell volume is hypothesized to translate into greater power output and muscular endurance. Studies suggest that betaine supplementation may improve the number of repetitions performed during resistance exercises like the squat and bench press.
This performance enhancement is due to the stabilization of cellular structures and the maintenance of hydration, optimizing the muscle cell’s ability to function under duress. The improved endurance and strength observed are typically associated with anaerobic performance, such as high-intensity weightlifting. Betaine may also indirectly support the synthesis of creatine by providing methyl groups to the methionine cycle.
Dietary Sources and Supplemental Forms
Betaine is widely distributed in the diet, with the richest sources found in certain whole foods.
Dietary Sources
- Sugar beets, from which the compound was first isolated.
- Vegetables like spinach.
- Wheat germ.
- Wheat bran, which are major contributors to dietary intake.
For individuals seeking specific health or performance benefits, betaine is available in supplemental forms. The form relevant to the metabolic and athletic functions discussed is betaine anhydrous, also known as trimethylglycine (TMG). This is the pure form used for homocysteine regulation and performance enhancement.
Another common supplemental product is betaine hydrochloride (Betaine HCl), but this is used for an entirely different purpose. Betaine HCl is primarily taken to increase stomach acid levels in people with low gastric acidity, as it provides a source of hydrochloric acid. It is important to differentiate between these two forms, as Betaine HCl is not used to achieve the methyl-donating or osmolyte effects of betaine anhydrous.