SMD 0.47
Lower-body strength
A real, modest bump in max strength (esp. legs) across 17 studies, 317 people — the most solid performance finding.
−1.3 µmol/L
Homocysteine
Reliably lowers this blood marker — the largest pooled analysis to date (62 studies).
<4 g/day
The dose that avoids the LDL question
Cholesterol effects show up mainly at ≥4 g/day and mainly in people with metabolic syndrome — not at the gym dose.
$0
What's patentable here
A natural molecule nobody owns — which is also why nobody's funding the big human trials.
Why the Evidence Looks Thin (It's Not the Molecule's Fault)
Follow the money
Betaine isn't controversial the way ivermectin is — nobody's suppressing it or ridiculing the doctors who use it. Its problem is smaller and more common: it's a natural compound found in beets, spinach, and wheat bran, and the U.S. Patent Office generally won't grant a patent on a natural product itself. No patent means no company can lock in exclusive profit from a $100M trial, so nobody pays for one. What you're left with is a real but modest evidence base built almost entirely on academic grants and small university labs — honest science, just underfunded relative to how cheap and widely used the compound is.
The pattern to notice: the compound with the most money behind it (a patented drug) gets the $100M trial; the compound anyone can buy in bulk for pennies gets a handful of 20-40 person university studies. That's not proof betaine doesn't work — it's a predictable consequence of who can profit from proving it. Judge the studies that exist on their own merits, and don't mistake "thin literature" for "doesn't work."
Where Betaine's Evidence Stands
PubMed
Betaine has a couple of real, replicated effects (lower-body strength, homocysteine) and a long list of thin or unproven ones (power, endurance, mood, fatty liver). The homocysteine effect carries a genuine, dose-dependent asterisk worth understanding — not fearing.
What the Evidence Actually Shows
PubMed
The number is the finding. Betaine's wins are specific and modest; its nuances are worth knowing before you form an opinion either way.
Maximal strength (legs)
SMD 0.47
Significant gain in max strength after ≥7 days, strongest in the lower body (SMD 0.49), plus a smaller but still significant vertical-jump improvement (SMD 0.36). 17 studies, 317 people, ages 15–60.
→ Zawieja et al., J Sports Sci 2024 · PMID 39514262
Homocysteine
−1.3 µmol/L
The largest pooled analysis to date (62 studies, five databases) confirms betaine reliably lowers blood homocysteine — the single most consistent thing it does, at any studied dose.
→ Ashtary-Larky et al., Crit Rev Food Sci Nutr 2021 · PMID 33764214
The lipid question, precisely
Dose-dependent
The same 62-study analysis found total cholesterol and LDL rose only at doses ≥4 g/day — with no adverse lipid effect below that threshold. A smaller, earlier meta of 6 RCTs at ≥4 g/day found total cholesterol rose modestly but LDL, HDL, and triglycerides did NOT change significantly — a more nuanced picture than "betaine raises LDL."
→ Ashtary-Larky 2021, above · Zawieja E et al., J Diet Suppl 2019 · PMID 31809615
Power, sprint, endurance, liver
No effect / mixed
The strength meta found no significant benefit for upper-body strength, cycling-sprint power, bench-throw power, or muscular endurance. A 12-month RCT in fatty-liver patients (20 g/day) found less worsening of steatosis but no significant change in fibrosis score.
→ Zawieja 2024, above · Abdelmalek et al., Hepatology 2009 · PMID 19824078
The LDL Question, In Full — Not Just the Headline
PubMed
EFSA
This is the one nuance worth getting exactly right, because different sources summarize it differently. Read the actual population and dose, not just the word "raises."
Who it was studied in
Overweight, metabolic syndrome
Specific group
The EFSA finding that triggered the "betaine raises LDL" headline was in overweight subjects with metabolic syndrome at 4 g/day — not in healthy people, and not at 3 g/day.
What EFSA actually set as the limit
400 mg/day food-additive UL
Not the trial dose
EFSA's official safe upper limit for betaine added to food products is 400 mg/day — a conservative regulatory ceiling, roughly 1/6th of the 2.5 g/day dose used in the strength trials. The two numbers answer different questions; don't confuse a food-fortification limit with "the dose that's dangerous."
What the biggest meta-analysis found
Everything else stayed flat
No change
Across all 62 pooled studies: no significant effect on triglycerides, HDL, fasting blood glucose, CRP, liver enzymes, or blood pressure. The lipid story is narrow and dose-specific, not a broad metabolic red flag.
→ Ashtary-Larky 2021 · PMID 33764214
The honest summary: at the ~2.5 g/day dose used in the strength studies, the LDL/cholesterol concern doesn't clearly apply. It shows up mainly at ≥4 g/day, most clearly in people who already have metabolic syndrome. If you're using the higher homocysteine-lowering dose (4–6 g/day) and you have metabolic risk factors, that's the specific situation to watch with a lipid panel — not a reason to avoid betaine across the board.
The Evidence Table
PubMed
The honest ledger — performance, homocysteine, lipids, and liver, ranked by the size and rigor of the underlying pool.
| # | Study / Source | Type | What it found |
|---|---|---|---|
| 1 | Betaine supplementation & cardiovascular markers |
Meta-analysis 62 studies |
Homocysteine ↓, lipids dose-dependent |
| 2 | Chronic betaine & exercise performance |
Meta-analysis 17 studies, 317 |
Modest (strength) |
| 3 | Betaine supplementation & total cholesterol |
Meta-analysis 6 RCTs, ≥4 g/day |
TC up, LDL unchanged |
| 4 | Betaine for nonalcoholic fatty liver disease |
RCT 55 NASH patients, 12 mo |
Modest / null |
| 5 | Betaine & adult-onset MTHFR deficiency |
Case report | Clinical improvement |
| 6 | Pre-workout (MIPS) context for betaine |
Review | Supporting role |
Reality check: betaine is a cheap, mostly-safe supplement with one modest, real win (lower-body strength) and one consistent biochemical effect (homocysteine) whose downstream heart benefit is unproven — and whose lipid trade-off is real but narrower than the popular summary suggests. A reasonable add-on for a lifter; a legitimate MTHFR-support option; not the methylation cure-all it's marketed as, and not the "hidden danger" a headline-only reading makes it sound like either.
Cost & Sources
Market data
Follow the money
Cheap in powder form, and genuinely free in your food. This is the whole reason it's underfunded: nobody makes a fortune selling it.
Free
Food (beets, spinach, wheat bran)
$0
extra — "betaine" literally means "from beets"
Whole-food baseline
Prescription
Cystadane (homocystinuria Rx)
$$$
medical use only
Same molecule, a patented formulation for a rare disease
The pattern again: the identical molecule costs pennies as a supplement and commands a premium as "Cystadane" once it's packaged as an approved drug for a narrow indication. The compound didn't change — the patent and the paperwork did.
Dosing Reality
Clinical / Research
The lifting dose and the homocysteine dose are different — and the higher one is where the lipid nuance from above actually applies.
Strength / gym
2.5 g/day
The dose used in most performance studies; below the range where lipid effects were seen
Homocysteine
4–6 g/day
Needed to reliably move homocysteine — the dose range where the dose-dependent lipid nuance applies
Upper limit
~6–20 g/day
Trials up to 20 g/day (NAFLD study) were tolerated; GI upset and body odor (trimethylamine) appear at higher intakes for some people
Consider checking
Your lipid panel
Reasonable if you use ≥4 g/day AND have metabolic syndrome or existing high cholesterol — not necessary at the gym dose
Legal & Regulatory Position — One Country's View Each
T1 · Regulatory
Betaine is a food component, a supplement, and — in one narrow case — an approved drug. Each regulator below is stating its own conflicted or conservative position, not a global verdict; none of them are the final word on whether the compound "works."
FDA (United States)
Supplement + a niche drug
Sold freely as a supplement, no premarket approval required; separately approved as the prescription drug Cystadane for homocystinuria, a rare genetic disorder. That narrow drug approval says nothing about general "health" use — a common mix-up in both directions.
EFSA (Europe)
Safe, with a conservative food-additive ceiling
Set a 400 mg/day upper limit for betaine added to foods — a cautious regulatory number, not a supplement-dose recommendation. Flagged the LDL finding in metabolic-syndrome subjects at 4 g/day as the basis for that caution. A food regulator being conservative about a food additive; read it as that, not as "Europe says betaine is dangerous."
Sport (WADA)
Not on the prohibited list
Betaine does not appear on the current WADA Prohibited List. As with any blended pre-workout, the practical risk is contamination from other ingredients — choose third-party-tested products.
PubMed vs. the Doctors + Real-World Use
PubMed
Community
Honest gap to name: unlike higher-profile compounds, we could not find a credentialed physician with substantive, on-record, betaine-specific claims worth quoting here — the functional-medicine and longevity-podcast world discusses TMG mostly in passing, as one ingredient in a broader methylation stack, without citable specifics. That thinness is itself consistent with the funding story above: a compound this un-marketable to prescribe doesn't generate the kind of expert commentary a patented drug does. We're not filling that gap with a manufactured quote.
Lifters
Stacked with creatine
Commonly added to creatine + caffeine in pre-workouts. Reports of a small strength/pump edge line up with the modest lower-body finding above.
Methylation / MTHFR community
Paired with NMN, folate
Widely used alongside NMN/NR and methylfolate to "support methylation," and there's a real mechanistic basis (the BHMT pathway bypasses the MTHFR bottleneck). One published case report backs clinical use in confirmed MTHFR deficiency; broader longevity claims remain thin in humans.
Livestock & aquaculture research (global)
Heavily studied — just not in people
Ironically, betaine has a much bigger, more international research base in animal agriculture — Japanese quail trials, Asia-Pacific poultry and aquaculture studies — than in human medicine. The molecule is well-understood biologically; it's specifically human trials that are scarce, for funding reasons, not safety reasons.
High-dose users
"Fishy" smell
At large doses some report a fishy body odor (trimethylamine) and GI upset — the practical ceiling for most people, well below where any organ-level harm has been shown.
→ RxList
Side Effects & Who Should Be Careful
Safety
Mostly easy-going. The one real trade-off is specific, dose-dependent, and now precisely scoped above — not a blanket warning.
Common side effects
Gut & odor
Nausea, stomach upset, or diarrhea, mostly at higher doses. Some people get a faint fishy body odor (trimethylamine). The 62-study pooled analysis found no significant effect on liver enzymes, blood pressure, or blood glucose at any studied dose.
Take ≥4 g/day →
Watch LDL if metabolic risk
Total cholesterol (and, in some pooled analyses, LDL) can rise at doses ≥4 g/day — the clearest signal is in people who already have metabolic syndrome. The gym dose (~2.5 g) sits below the range where this shows up.
Talk to your doctor first if…
Watch lipids
You have existing high cholesterol or metabolic syndrome and plan to use the higher 4–6 g/day dose (check a lipid panel), have kidney issues, or are pregnant/nursing.
→ RxList
The honest safety bottom line: at the lifting dose (~2.5 g/day), betaine's downside is genuinely low — no demonstrated organ toxicity across doses tested up to 20 g/day in trials. The one thing worth tracking is cholesterol if you go to the higher 4–6 g/day dose AND already carry metabolic risk factors. Low risk, real modest benefit, trivial cost — the honest math favors trying it for the uses it's actually shown to help with.
The Bottom Line — In Plain English
What it is
Betaine (a.k.a. TMG, trimethylglycine) is a compound originally isolated from beets. Your body uses it to recycle homocysteine and to donate "methyl groups" — and it's too cheap and unpatentable for anyone to fund a huge human trial on it.
What the research shows
A modest, real boost to lower-body strength, and it reliably lowers homocysteine. Little to nothing proven yet for power, endurance, mood, or fatty-liver reversal — not because it fails, but because the trials are small and short.
How it's used
~2.5 g/day for the gym; 4–6 g for homocysteine/methylation support. Cheap, and also free in beets, spinach, and whole wheat.
Legality & safety
Legal supplement (and a niche, patented Rx drug for the same molecule). No demonstrated organ toxicity at studied doses. The one real nuance: LDL/cholesterol can rise at ≥4 g/day, mainly in people with metabolic syndrome. Not on WADA's prohibited list.
The honest verdict
A fine, cheap, low-risk add-on for a lifter at ~2.5 g, and a legitimate MTHFR-support option at higher doses. Be skeptical of "methylation/longevity cure-all" marketing that outpaces the (thin, underfunded) human data — and if you go high-dose with metabolic risk factors, check a lipid panel.
- Betaine gives a modest, real boost to lower-body strength (and vertical jump) — but not to power, sprinting, or endurance.
- It reliably lowers homocysteine at any studied dose, in the largest meta-analysis to date (62 studies) — whether that translates to fewer heart attacks specifically is still unproven, same as most homocysteine-lowering strategies.
- The LDL/cholesterol trade-off is real but narrower than the popular summary: it shows up mainly at ≥4 g/day and mainly in people with metabolic syndrome, not at the 2.5 g gym dose.
- The thin human evidence base isn't a sign the compound doesn't work — it's a predictable result of being a natural, unpatentable molecule nobody can corner the market on.
- It's cheap (~$0.15/serving), shows no organ toxicity at studied doses, and is free in beets and spinach — a legitimate low-risk option, not a proven cure-all.