Anhydrous betaine (trimethylglycine)
Anhydrous betaine (TMG) is a compound naturally present in various foods (e.g. beetroot, spinach, cereals) and also produced from the oxidation of choline. In human physiology it acts mainly as a methyl donor in the methionine cycle (via BHMT) and as a compatible osmolyte, contributing to the regulation of cell volume. In the “performance” field, the literature shows heterogeneous results: some studies report improvements in strength/power parameters or body composition, while others do not show significant differences.
Methyl group donor and osmoprotectant: potential support for performance and cellular homeostasis
Anhydrous betaine (TMG) is a compound naturally found in various foods (e.g. beetroot, spinach, cereals) and also produced through the oxidation of choline. In human physiology, it acts primarily as a methyl donor in the methionine cycle (via BHMT) and as a compatible osmolyte, contributing to the regulation of cell volume. In the “performance” field, the literature shows mixed results: some studies report improvements in strength/power parameters or body composition, while others do not show significant differences.
Mechanism of action
1) Methyl donation (BHMT pathway): TMG transfers a methyl group to homocysteine, forming methionine, thereby helping maintain the methionine pool and, indirectly, S-adenosylmethionine (SAMe), the main methyl donor for many reactions (e.g. methylation of DNA/proteins/lipids and creatine synthesis). 2) Compatible osmolyte: it increases the cell’s ability to handle changes in osmolarity, potentially supporting intracellular hydration and protein stability. 3) Effects on cardiometabolic markers: in some contexts it may reduce homocysteine (especially if elevated and/or in the presence of specific nutritional conditions), but it may also increase TMAO (trimethylamine N-oxide) through microbial metabolism of trimethylamine, a safety aspect that is still under debate. 4) Possible influence on body composition and neuromuscular output: hypotheses include improved cellular hydration status, modulation of energy metabolism, and indirect support for creatine availability (via methyl sparing), but clinical results are variable.
Supported benefits
- Reduction of plasma homocysteine in some individuals (especially with elevated homocysteine or in specific nutritional contexts) (moderate)
- Small/inconsistent improvements in strength/power and performance in muscular endurance exercises in some studies on trained individuals (limited)
- Possible favorable changes in body composition (lean/fat mass) in some protocols, but with results not uniformly replicated (limited)
- Support as an osmoprotectant (hydration/cell volume) with biological plausibility, but direct evidence on sports outcomes remains inconclusive (emerging)
Safety & side effects
- Gastrointestinal disturbances (nausea, cramps, diarrhea), more likely at high doses or with a single intake
- Possible increase in TMAO in some individuals (dependent on microbiota and diet), with clinical significance not yet fully clarified
- Rare “fishy” body odor (more typical of trimethylaminuria or metabolic predispositions, but reported with trimethylated compounds)
- Possible changes in plasma lipids in some studies (results are not consistent; monitoring is advisable in individuals with dyslipidemia)
FAQ
Are betaine and “beta-alanine” the same thing?
No. Betaine (TMG) is a methyl donor/osmolyte; beta-alanine is an amino acid used to increase muscle carnosine. Their mechanisms and evidence differ.
Does betaine definitely improve strength and muscle mass?
No. Some studies show improvements, while others show no differences compared with placebo. If an effect is present, it tends to be modest and depends on the protocol, population, and training.
Is it useful if homocysteine is high?
It may reduce homocysteine in some cases, but elevated homocysteine may depend on folate/B12/B6 deficiencies, genetics, medications, or clinical conditions. Management requires professional evaluation and is not based solely on one supplement.
What is the relationship between betaine and creatine?
Endogenous creatine synthesis requires methyl groups (SAMe). Betaine may help maintain the methyl pool via the BHMT pathway, but this does not automatically imply a performance increase comparable to direct creatine supplementation.
Is the TMAO issue a definite problem?
It is not “definite” in an individual clinical sense: TMG may increase TMAO in some individuals, but the causal relationship between TMAO and cardiovascular risk is complex and influenced by diet, microbiota, and metabolic context. It is a point of caution, especially in at-risk individuals.
The information provided is for informational and educational purposes only. It does not constitute medical advice. Use must be evaluated and authorized by a qualified healthcare professional.
Mechanism of action
1) Methyl donation (via BHMT): TMG transfers a methyl group to homocysteine, forming methionine, helping maintain the methionine pool and, indirectly, S-adenosylmethionine (SAMe), the main methyl donor for many reactions (e.g. methylation of DNA/proteins/lipids and creatine synthesis). 2) Compatible osmolyte: increases the cell’s ability to handle changes in osmolarity, potentially promoting intracellular hydration and protein stability. 3) Effects on cardiometabolic markers: in some contexts it may reduce homocysteine (especially if elevated and/or in the presence of specific nutritional conditions), but it may also increase TMAO (trimethylamine N-oxide) via microbial metabolism of trimethylamine, a safety issue that is still debated. 4) Possible influence on body composition and neuromuscular output: hypotheses include improved cellular hydration status, modulation of energy metabolism, and indirect support for creatine availability (via methyl sparing), but clinical results are variable.
Scientific benefits
Contraindications
- Pregnancy and breastfeeding: insufficient safety data for high-dose supplementation (professional evaluation required)
- Suspected or known trimethylaminuria (TMAU): risk of worsening body odor due to trimethylamine accumulation
- Significant kidney or liver disease: metabolism and excretion may be altered; clinical evaluation required
- Hyperhomocysteinemia secondary to folate/B12 deficiencies: TMG may not replace correction of the nutritional cause
Side effects
- Gastrointestinal disturbances (nausea, cramps, diarrhea), more likely at high doses or when taken as a single dose
- Possible increase in TMAO in some individuals (dependent on the microbiota and diet), with clinical significance not yet fully clarified
- Rare “fishy” body odor (more typical of trimethylaminuria or metabolic predispositions, but reported with trimethylated compounds)
- Possible changes in plasma lipids in some studies (results are not consistent; monitoring is advisable in subjects with dyslipidemia)
Interactions
- Methotrexate and drugs that interfere with folate metabolism: management of homocysteine and methylation status requires clinical supervision; avoid self-management
- Lipid-lowering drugs or conditions requiring lipid monitoring: possible changes in lipids suggest caution and monitoring
- Diet rich in TMA precursors (e.g. carnitine, choline) and specific microbiota compositions: possible increase in TMAO; individual relevance varies
Regulatory status
Generally marketed as a dietary supplement (TMG/anhydrous betaine) in the EU and USA; it is not typically included on WADA lists as a prohibited substance, but athletes should check specific regulations and the risk of contamination from uncertified products.
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