TMG: The Methyl Donor That’s Crucial for Anyone With Elevated Homocysteine
Trimethylglycine (TMG) — also called betaine anhydrous — is a simple compound that plays an outsized role in a critical biochemical pathway: the methylation cycle. TMG is a methyl donor — it provides methyl groups for the conversion of homocysteine to methionine, which is then used to produce S-adenosylmethionine (SAMe), the body’s universal methyl donor. In plain terms, TMG is one of the most efficient ways to lower elevated homocysteine, which is one of the most important modifiable risk factors for cardiovascular disease, stroke, and neurodegeneration. When TMG donates a methyl group to homocysteine, it converts it to methionine — effectively removing it from circulation. This is why TMG (and betaine) supplementation has become a key intervention in any functional medicine approach to elevated homocysteine.
Homocysteine is an amino acid that is produced as a normal part of the methylation cycle. When it’s properly metabolised, it’s converted to methionine (which is useful) or cysteine (also useful). But when the methylation cycle is sluggish — typically due to inadequate B vitamins (B12, B6, folate) or genetic variations like MTHFR mutations — homocysteine accumulates. Elevated homocysteine (>12 μmol/L) is associated with increased cardiovascular disease risk, increased risk of cognitive decline and Alzheimer’s, increased risk of blood clots, and various other health concerns. The conventional approach to lowering homocysteine is B vitamins; TMG provides a complementary approach by directly donating methyl groups to the conversion pathway.
TMG vs Betaine: Are They the Same?
The terms TMG and betaine are often used interchangeably, and they are the same molecule — trimethylglycine is simply the more precise chemical name for betaine. However, it’s important to note that “betaine” can sometimes refer to betaine HCl (betaine hydrochloride), which is a different compound used as a digestive aid (discussed in our betaine HCl article). When people refer to betaine for methylation support and homocysteine lowering, they mean betaine anhydrous (TMG). TMG as a supplement typically comes in powdered form and is dosed at 1.5–6 grams daily, divided into two or three doses, for homocysteine-lowering applications.
TMG is found in food — particularly in beets, spinach, and quinoa — but dietary intake is far below the doses needed to meaningfully affect homocysteine. For someone with elevated homocysteine (>12 μmol/L), TMG supplementation at therapeutic doses is more effective than dietary approaches. TMG is often used alongside B vitamins (particularly methylfolate and methylcobalamin) and other methyl donors for a comprehensive homocysteine-lowering protocol. The combination is more effective than any single approach because TMG and B vitamins address different parts of the homocysteine metabolism pathway.
Key Takeaways
TMG (betaine anhydrous) is an efficient methyl donor that directly lowers elevated homocysteine by converting it to methionine. Homocysteine >12 μmol/L is a significant cardiovascular and neurological risk factor. Effective dose for homocysteine lowering is 1.5–6 grams daily. Combine with B vitamins (methylfolate, methylcobalamin, B6) for comprehensive homocysteine management. Dietary betaine (from beets, spinach) is far below therapeutic doses.
Iron Role in Brain Energy Metabolism
Iron is essential for brain function far beyond its role in haemoglobin and oxygen transport. The brain consumes approximately 20% of the body oxygen despite accounting for only 2% of body weight, and iron is critical in this energy metabolism — particularly in the electron transport chain within mitochondria, where iron-sulfur clusters are essential components of Complexes I, II, and III. Iron is also a cofactor for tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis, and for ribonucleotide reductase, the enzyme required for DNA synthesis. These roles mean that iron deficiency — even without frank anaemia — can impair dopaminergic signalling, reduce neural energy production, and compromise myelin formation, with measurable effects on attention, memory, and executive function.
Why Iron Deficiency Is So Common
Iron deficiency is the most common nutritional deficiency worldwide, affecting an estimated 2 billion people. In menstruating women, iron deficiency is particularly prevalent due to monthly menstrual blood loss — even a “normal” menstrual iron loss of 30-40ml per cycle can gradually deplete iron stores over months to years. In men and post-menopausal women, iron deficiency should always be investigated as it can signal occult gastrointestinal blood loss. The symptoms of iron deficiency extend well beyond fatigue and pallor: restless legs syndrome (strongly associated with brain iron deficiency), impaired thermoregulation, reduced exercise tolerance, and cognitive impairment in both children and adults.
Iron Status: Not Just Haemoglobin
The standard diagnostic marker for iron deficiency is haemoglobin — but this misses the majority of iron-deficient people, because haemoglobin only falls after iron stores (ferritin) are already significantly depleted. Ferritin is the storage form of iron, and a level below 30 ng/mL indicates depleted stores, while anything below 15 ng/mL indicates frank deficiency. Optimal ferritin for cognitive function appears to be in the range of 50-100 ng/mL. Iron supplementation should always be guided by ferritin testing, not haemoglobin alone, and excessive iron (from over-supplementation or haemochromatosis) carries its own serious risks including liver cirrhosis and increased infection risk through iron-dependent pathogen growth.
Leave a Reply