TMG (Betaine / Trimethylglycine)

What is TMG (Betaine / Trimethylglycine)?

TMG, short for trimethylglycine and also called betaine, is a small molecule originally isolated from sugar beets. Your body makes some of it and you get more from foods like beets, spinach, and whole grains. Its main job is donating “methyl groups”, tiny chemical tags the body uses for countless background tasks, including keeping a compound called homocysteine in check. In the longevity world it is best known as the sidekick supplement people pair with NMN or NR to replace methyl groups those compounds are thought to use up.

What does TMG (Betaine / Trimethylglycine) claim to do?

The headline claims: it keeps homocysteine in a healthy range (relevant because elevated homocysteine is linked to cardiovascular and brain aging), supports liver health, replenishes methyl groups depleted by NAD-boosters, and gives athletes a small edge in power and strength. Some users also report better mood and energy, which they attribute to smoother methylation.

Why do people use TMG (Betaine / Trimethylglycine)?

TMG rode into popularity on the coattails of NMN. The theory goes that boosting NAD heavily uses methyl groups, and TMG tops them back up, so the two are sold and stacked together constantly. Beyond that, it is cheap, has a clean safety record at sane doses, and the homocysteine angle appeals to people thinking about long-term heart and brain health. Lifters add it for the modest performance data.

What does the science actually say about TMG (Betaine / Trimethylglycine)?

The most solid human finding is straightforward: TMG reliably lowers homocysteine. This is well established across studies, supplementing betaine brings elevated homocysteine down in a dose-dependent way. The honest catch is that lowering homocysteine with supplements has not been clearly shown to translate into fewer heart problems or longer life. High homocysteine is associated with cardiovascular and cognitive aging, but pushing the number down with a pill has not reliably moved the outcomes that matter. So the marker improves; the proof that it changes your future is incomplete.

For athletic performance, there is a reasonable cluster of small studies suggesting betaine may modestly support strength, power output, and body composition in trained people, though results are mixed and the effect is small. Liver-support claims rest mostly on its role in fat metabolism and some early data, not on robust outcome trials.

The “replenish methyl groups depleted by NMN” rationale is mechanistically plausible and widely repeated, but it is largely theory. There is little direct human evidence showing that NMN users specifically need TMG or benefit from adding it. It is a sensible insurance policy, not a proven necessity.

How do people use TMG (Betaine / Trimethylglycine)?

Common doses run 500–2,000 mg daily, often split or taken with a meal. Athletes typically use around 2,500 mg daily for performance. People stacking it with NAD-boosters usually take 500–1,000 mg alongside their NMN or NR. It is taken as a daily ongoing supplement rather than a short course.

Is TMG (Betaine / Trimethylglycine) safe? Risks and who should skip it

TMG is generally well tolerated. At higher doses it can nudge LDL cholesterol upward in some people and may cause a fishy body odor or mild stomach upset. Because it affects methylation and homocysteine pathways, anyone with kidney disease, a known methylation disorder, or cardiovascular conditions should check with a doctor. Pregnant or breastfeeding people and those on prescription medication should clear it first.

The bottom line on TMG (Betaine / Trimethylglycine)

TMG is cheap and genuinely lowers homocysteine, which is a reasonable reason to consider it, especially if your levels run high. Just be clear-eyed that the “lower marker equals longer life” link is not proven, and the NMN-pairing rationale is sensible theory rather than settled fact.