Betaine, also known as trimethylglycine (TMG), is a naturally occurring compound derived from the amino acid glycine — structurally distinguished by the addition of three methyl groups. It belongs to a broader chemical class also called betaines, characterised by their zwitterionic structure (carrying both positive and negative charges within the same molecule). Despite its relative obscurity in mainstream nutrition conversations, betaine is involved in some of the body's most fundamental biochemical processes, including methylation, liver metabolism, and cardiovascular health. It also appears in two pharmacologically distinct supplementation contexts — as TMG for systemic methylation support, and as Betaine HCL for digestive function — which are worth understanding separately.
Natural Sources of Betaine
The name "betaine" derives directly from Beta vulgaris — the beetroot — from which it was first isolated in the 19th century. Beetroot remains one of the richest dietary sources, but betaine is widely distributed across plant and animal foods:
- High-betaine plant sources — beetroot, spinach, quinoa, wheat germ, and wheat bran
- Animal sources — shellfish (particularly shrimp), turkey, and lamb
- Other sources — whole grains including bulgur and rye
In the body, betaine is also synthesised endogenously from choline (vitamin B4) through an oxidation pathway — which is one reason why choline status and betaine status are closely linked. This relationship is particularly relevant during pregnancy, when demand for both compounds is elevated. Average dietary betaine intake from food is estimated at 100–300 mg per day, which is considerably below the doses used in research on its functional effects.
TMG: Betaine as a Methyl Donor
The most significant biochemical role of betaine (TMG) is as a methyl donor in the one-carbon metabolic cycle. In this process, betaine donates one of its three methyl groups to homocysteine, converting it into methionine — a reaction catalysed by the enzyme betaine-homocysteine methyltransferase (BHMT), primarily in the liver and kidneys.
This conversion is important for two reasons. First, it helps maintain healthy homocysteine levels: elevated homocysteine is an established risk factor for cardiovascular disease, and betaine supplementation has been shown in clinical research to measurably reduce circulating homocysteine concentrations. Second, the methionine produced feeds into the synthesis of S-adenosylmethionine (SAM), the body's primary universal methyl donor, which participates in hundreds of enzymatic reactions including DNA methylation, neurotransmitter synthesis, and the production of creatine. The relationship between betaine, homocysteine regulation, and heart health makes TMG a compound of genuine interest in cardiovascular research, and products supporting this area can be explored in our cardiovascular supplements collection.
Betaine and Liver Function
The liver is the primary site of betaine metabolism and also one of the organs that may benefit most from adequate betaine status. Betaine supports liver function through two mechanisms: its role in homocysteine methylation (reducing the hepatotoxic burden of elevated homocysteine) and its contribution to phosphatidylcholine synthesis, which is critical for normal hepatic fat metabolism.
Research has examined betaine's potential role in non-alcoholic fatty liver disease (NAFLD), where impaired fat export from liver cells leads to pathological fat accumulation. Animal and some human studies suggest betaine supplementation may support hepatic fat metabolism, though this research is ongoing and betaine should not be considered a treatment for liver conditions. The choline-betaine relationship is particularly relevant here: choline deficiency and low betaine status are both associated with impaired liver fat export, suggesting that the two compounds work in a complementary fashion to maintain healthy hepatic metabolism.
Betaine as a Sports Supplement
TMG has attracted growing interest as a performance supplement in the sports nutrition space. Several mechanisms are proposed: betaine's role in creatine synthesis (methionine, produced via betaine-dependent methylation, is a precursor to creatine), its potential osmolyte function (protecting cells from osmotic stress during exercise), and direct effects on protein synthesis pathways.
Human clinical trials on betaine supplementation in athletes have shown mixed but generally positive results for muscular power output, endurance capacity, and body composition metrics. The most commonly used doses in research are 2–2.5 g per day, typically split between a morning dose and a pre- or post-workout dose. While betaine is not a primary performance supplement in the same category as creatine or caffeine, the evidence base for its supporting role in strength and endurance training is growing. Explore our amino acids collection for TMG and related compounds.
[tip:For sports performance applications, betaine (TMG) is most commonly taken in total daily doses of 2–2.5 g, divided between morning and around training time. It can be taken alongside creatine, as the two compounds have complementary mechanisms. Always take with food to minimise the risk of digestive discomfort.]Betaine HCL: A Different Application
Betaine hydrochloride (Betaine HCL) is a pharmacologically distinct product from TMG, though they share the same base molecule. Betaine HCL is a compound of betaine and hydrochloric acid that, when dissolved in stomach fluid, releases HCl — temporarily increasing gastric acidity. It is used specifically to support digestive function in individuals with low stomach acid (hypochlorhydria), a condition that can impair the absorption of nutrients including calcium, vitamin B12, iron, and protein.
Low stomach acid is more common than often recognised, particularly in older adults, those using proton pump inhibitors long-term, and individuals with certain autoimmune conditions. Symptoms can include bloating after meals, a sense of fullness, and poor tolerance of protein-rich foods. Betaine HCL — often combined with pepsin, a protein-digesting enzyme — is used to restore more normal gastric pH in these circumstances. It is frequently paired with gentian bitters or digestive enzyme complexes to support broader digestive function. Our digestive system supplements collection includes a range of Betaine HCL formulations and complementary digestive support products.
[warning:Betaine HCL is not appropriate for everyone. Do not use it if you have a history of gastric ulcers, gastritis, acid reflux, or are taking NSAIDs (ibuprofen, aspirin, naproxen), as these combinations can cause or worsen gastric irritation or bleeding. Always start with the lowest dose and assess tolerance. Consult a healthcare professional before use if you have any gastrointestinal conditions or are taking medication. TMG (trimethylglycine) is generally better tolerated but should be used with appropriate caution in those with cardiovascular conditions or elevated homocysteine who are under medical supervision.]Choosing Between TMG and Betaine HCL
The distinction matters in practice. TMG supplements are the appropriate choice for those interested in homocysteine management, liver metabolism support, cardiovascular health, or sports performance. Betaine HCL is specifically a digestive aid for those with symptoms suggesting low gastric acidity, and is taken before meals rather than around training. They are not interchangeable, and many people who would benefit from one have no particular need for the other.
TMG / Trimethylglycine supplements:
[products: now-foods-tmg-betaine-1000-mg-100-tablets, swanson-tmg-trimethylglycine-500-mg-90-capsules, life-extension-tmg-500-mg-60-veg-capsules, 7nutrition-tmg-250-g, aliness-vitamin-b-complex-b-50-methyl-plus-tmg-100-veg-capsules]Betaine HCL supplements for digestive support:
[products: aliness-betaine-hcl-pepsin-650-150-mg-100-veg-capsules, now-foods-betaine-hcl-648-mg-120-veg-capsules, doctors-best-betaine-hcl-pepsin-gentian-bitters-120-capsules, thorne-research-betaine-hcl-pepsin-225-capsules, enzymedica-betaine-hcl-120-capsules, medverita-betaine-hcl-pepsin-120-capsules] [note:All Medpak products are shipped from within the European Union, ensuring fast and reliable delivery across Europe with no customs fees or import complications.]
