Betaine
Betaine (trimethylglycine), a methyl donor and osmolyte
Written by Aaron CuhaReviewed Sep 2026
Also known as: TMG, Trimethylglycine, Glycine betaine, Betaine anhydrous, Cystadane
Six grams a day lowers fasting homocysteine by 20 percent in healthy adults and raises LDL cholesterol by 0.36 mmol/L in the same randomised studies. The trials that lowered homocysteine by other means and then counted heart attacks found nothing: 12,064 survivors, homocysteine down 28 percent, vascular event risk ratio 1.04.
Overview
Betaine is the cleanest example in this batch of a compound that does exactly what it says on the bottle, where what it says on the bottle turns out not to be the point.
It lowers homocysteine, reliably and dose-dependently. In 76 healthy adults given 1.5, 3 or 6 grams a day for six weeks, fasting homocysteine fell 12, 15 and 20 percent respectively against placebo, and the rise after a methionine load fell by 23, 30 and 40 percent. Those are large, consistent, placebo-controlled effects at doses inside the range of ordinary dietary intake.
The same research group then pooled the blood lipid data from their betaine studies and found what the abstract of the efficacy paper had no reason to mention. Betaine at 6 grams a day for six weeks raised LDL cholesterol by 0.36 mmol/L, roughly 14 mg/dL, raised triacylglycerol by 0.14 mmol/L, and raised the ratio of total to HDL cholesterol by 0.23. Lower doses raised LDL too without reaching significance. The effect was evident within two weeks. Their own conclusion is that the adverse effects on blood lipids may undo the potential benefits for cardiovascular health of betaine supplementation through homocysteine lowering. A later meta-analysis of six randomised trials at four grams a day or more found a pooled rise in total cholesterol of 0.34 mmol/L.
And then there is the question underneath both findings, which is whether lowering homocysteine does anything. That has been tested hard. In 12,064 myocardial infarction survivors followed 6.7 years, folic acid and vitamin B12 lowered homocysteine by a mean 3.8 micromol/L, a 28 percent reduction, and major vascular events occurred in 25.5 percent on treatment against 24.8 percent on placebo, a risk ratio of 1.04. The Cochrane review of homocysteine-lowering interventions found no difference against placebo for myocardial infarction or death from any cause, with a small favourable difference for stroke, and its trial sequential analysis concluded that further trials are unlikely to change the answer.
None of this touches the one place betaine has a proven clinical role. Betaine anhydrous is an approved prescription medicine for homocystinuria, an inherited disorder where homocysteine is not a risk marker but a poison at concentrations an order of magnitude above normal. That is a deficiency-shaped problem with a real endpoint, and it is a different situation entirely from taking TMG because you saw it in a stack.
Mechanism of action
Betaine donates a methyl group to homocysteine through betaine-homocysteine methyltransferase, regenerating methionine. This is the alternative to the folate and vitamin B12 route, and it runs mainly in liver and kidney, which is why betaine lowers homocysteine even when folate status is adequate. It is also a major organic osmolyte, accumulating in cells to maintain volume under osmotic stress, which is the basis of most of the athletic performance claims. The lipid effect is thought to be downstream of the same methylation chemistry: driving the betaine-homocysteine methyltransferase reaction changes hepatic S-adenosylmethionine availability and phosphatidylcholine synthesis, which feeds very low density lipoprotein assembly and export. That is a plausible route rather than a demonstrated one; the trials that found the effect were not designed to explain it.
Human evidence
Extensive and internally contradictory in an instructive way. Betaine's effect on homocysteine is among the best-established supplement effects in existence. Its effect on blood lipids points the other way, and the premise that links the first effect to a health outcome has been tested at scale and did not hold.
- 76 healthy adults, six weeks: fasting homocysteine down 12, 15 and 20 percent on 1.5, 3 and 6 grams a day.
- Pooled across three randomised betaine studies (151 participants): LDL cholesterol up 0.36 mmol/L and triacylglycerol up 0.14 mmol/L at 6 grams a day, evident within two weeks.
- Meta-analysis of six randomised trials at 4 grams a day or more: total cholesterol up 0.34 mmol/L; no significant pooled effect on LDL specifically.
- SEARCH trial, 12,064 heart attack survivors: homocysteine down 28 percent with B vitamins, major vascular events risk ratio 1.04 over 6.7 years.
- Cochrane 2017: no effect of homocysteine lowering on myocardial infarction or all-cause death; small favourable effect on stroke.
- Betaine anhydrous is an approved prescription treatment for homocystinuria, where homocysteine is the disease rather than a risk marker.
- No trial has measured lifespan, healthspan or any ageing endpoint with betaine supplementation.
What this does not tell you: The homocysteine and lipid findings come largely from one research group's set of short studies in healthy volunteers, with partial food industry funding disclosed. The two pooled lipid analyses disagree on whether the LDL rise specifically survives meta-analysis, and that disagreement should not be resolved by picking the friendlier one. Most importantly, the outcome trials that undercut the whole premise used B vitamins rather than betaine; nobody has run a cardiovascular outcome trial of betaine itself, and on current evidence nobody has a reason to.
Reading the research record
A surrogate endpoint is a measurement that stands in for the thing you care about, on the assumption that moving it moves the outcome. That assumption has failed often enough to be treated as a claim rather than a given. Homocysteine is the canonical case: it predicts cardiovascular disease strongly in observational data, it can be lowered reliably by several cheap interventions, and when trials lowered it and then counted heart attacks, the events did not fall. The lesson is not that markers are worthless. It is that a trial reporting a marker has answered a smaller question than the one the buyer is asking, and the page should say which question was answered.
Betaine belongs on this site because it is the compound where the biomarker-versus-outcome gap was measured rather than argued about. Homocysteine had everything a surrogate is supposed to have: a strong dose-response with disease in observational data, biological plausibility through vascular damage, and cheap reliable interventions to lower it. Then the trials were run, in tens of thousands of people, and the events did not fall. That result is the reason this archive treats a marker as a stopping rule rather than as a goal.
Two practical consequences follow. If you are taking betaine to lower homocysteine, you can watch the marker move and you will be watching something real, and the best available evidence says it will not change your cardiovascular risk. And if you take it anyway, check a lipid panel, because the same trials that lowered homocysteine raised LDL and triglycerides in the same people over the same weeks.
This archive's stated position on supplements is that you take something because a number on your bloodwork is out of range, and that you retest and stop if the number does not move. Applying that rule to this group is uncomfortable, because for most of them there is no deficiency state to correct and therefore no marker that tells you whether the bottle is doing anything. Where a compound here does move a readable number, the number is a surrogate rather than a deficiency, so moving it is not the same as fixing something that was broken.
The evidence, charted
Fig. 1 · evidence composition
3of 5 citations (60%) are in people
Counted from the citation list on this page. The Human count is the same number shown in the badge at the top. Both understate any literature larger than the sources we cite.
Fig. 2 · evidence over time
Evidence spans 5 distinct years, 2003 to 2021, counted from the citation list on this page.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four jurisdictions shown. A jurisdiction's classification is a regulatory fact, not a verdict on the science; see Legal status below for the full text and any notes.
Key studies & citations
- Human2003
Low dose betaine supplementation leads to immediate and long term lowering of plasma homocysteine in healthy men and women.
Four groups of 19 healthy adults took 1.5, 3 or 6 grams of betaine or placebo daily for six weeks. Fasting homocysteine after six weeks was 12 percent (p < 0.01), 15 percent (p < 0.002) and 20 percent (p < 0.0001) below placebo. The rise after methionine loading was 23, 30 and 40 percent lower at six weeks. Doses inside ordinary dietary range lower homocysteine.
Journal of Nutrition - Human2005
Effect of homocysteine-lowering nutrients on blood lipids: results from four randomised, placebo-controlled studies in healthy humans.
Pooled blood lipid data from four placebo-controlled randomised studies, including three of betaine totalling 151 participants. Betaine at 6 g/d for six weeks raised LDL cholesterol by 0.36 mmol/L (95 percent CI 0.25 to 0.46), triacylglycerol by 0.14 mmol/L and the total to HDL ratio by 0.23, with no effect on HDL. Lower doses also raised LDL without significance, and the LDL effect was already evident at two weeks. Folic acid had no effect on lipids. The authors conclude the lipid effects may undo the potential cardiovascular benefit of homocysteine lowering. Funding was 29 percent industrial through a food science consortium, disclosed in the paper.
PLoS Medicine - Review2021
Betaine Supplementation Moderately Increases Total Cholesterol Levels: A Systematic Review and Meta-Analysis.
Six randomised placebo-controlled trials published between 2002 and 2018, all at 4 g a day or more for six to twenty-four weeks. Pooled effect on total cholesterol 0.34 mmol/L (95 percent CI 0.02 to 0.65, p = 0.0352). No significant pooled effect on LDL, HDL or triglycerides, which is a weaker LDL signal than the 2005 pooled analysis found and is worth stating alongside it.
Journal of Dietary Supplements - Human2010
Effects of homocysteine-lowering with folic acid plus vitamin B12 vs placebo on mortality and major morbidity in myocardial infarction survivors: a randomized trial.
12,064 myocardial infarction survivors randomised double blind to 2 mg folic acid plus 1 mg vitamin B12 daily or placebo, followed 6.7 years. Homocysteine fell by a mean 3.8 micromol/L, 28 percent. Major vascular events occurred in 1,537 of 6,033 on treatment (25.5 percent) against 1,493 of 6,031 on placebo (24.8 percent), risk ratio 1.04 (95 percent CI 0.97 to 1.12, p = 0.28). The marker moved and the outcome did not. This trial used B vitamins rather than betaine, which is the point: it tests the premise, not the product.
JAMA - Review2017
Homocysteine-lowering interventions for preventing cardiovascular events.
Third update of the Cochrane review. No difference between homocysteine-lowering supplements of vitamins B6, B9 or B12 and placebo for myocardial infarction, death from any cause or adverse events; a small difference favouring treatment for stroke. Trial sequential analysis concluded that additional trials versus placebo are unlikely to increase certainty about the finding.
Cochrane Database of Systematic Reviews
Frequently asked questions
Does TMG lower homocysteine?
Yes, reliably. Six grams a day lowered fasting homocysteine 20 percent against placebo over six weeks in healthy adults, and even 1.5 grams a day, inside normal dietary range, lowered it 12 percent. This is one of the most reproducible supplement effects on any blood marker.
So does that lower my heart attack risk?
The evidence says no. In 12,064 heart attack survivors, lowering homocysteine 28 percent produced a major vascular event risk ratio of 1.04 over 6.7 years. The Cochrane review found no effect on myocardial infarction or all-cause death and concluded further placebo-controlled trials are unlikely to change that. Those trials used B vitamins rather than betaine, but they test the premise the betaine claim depends on.
Does betaine raise cholesterol?
In the pooled analysis of three randomised betaine studies, 6 grams a day raised LDL cholesterol 0.36 mmol/L and triacylglycerol 0.14 mmol/L, with the LDL effect visible by two weeks. A later meta-analysis of six trials at 4 grams a day or more found total cholesterol up 0.34 mmol/L but no significant pooled LDL effect. The two analyses disagree on the LDL specifically; both find a rise in total cholesterol. If you take it, get a lipid panel.
Is betaine a prescription drug?
Betaine anhydrous is, for homocystinuria, an inherited disorder in which homocysteine accumulates to concentrations far above normal and causes direct harm. That approval is the reason betaine has a serious safety record, and it is not evidence for taking TMG when your homocysteine is normal or mildly raised.
What about betaine for gym performance?
That is a separate literature built on betaine's role as a cellular osmolyte, and it is not covered by the trials on this page. Nothing in the homocysteine or lipid data speaks to it either way, and the lipid finding applies regardless of why you are taking the compound.
Is there any anti-ageing evidence?
None. No trial has measured lifespan, healthspan or any ageing endpoint with betaine. It appears in longevity stacks because of its role in methylation, which is a mechanism rather than a result.