SMD 0.47
Lower-body strength
A real, modest bump in max strength (esp. legs) across 17 studies — the most solid performance finding.
−5 to 20%
Homocysteine
Reliably lowers this blood marker at 4–6 g/day — but see the catch below.
↑ LDL
The cholesterol catch
The same 4 g+ dose that lowers homocysteine can raise LDL cholesterol — especially in metabolic syndrome.
~$0.15
Per serving
Cheap. The lifting dose is ~2.5 g/day; it's also free in beets, spinach & whole wheat.
Where Betaine's Evidence Stands
PubMed
Betaine has a couple of real but modest effects (lower-body strength, homocysteine) and a long list of thin or null ones (power, endurance, mood). And one effect — lowering homocysteine — comes with an asterisk.
What the Evidence Actually Shows
PubMed
The number is the finding. Betaine's wins are specific and modest; its misses are worth knowing before you pay for it.
Maximal strength (legs)
SMD 0.47
Significant gain in max strength after ≥7 days, strongest in the lower body (SMD 0.49), plus a small vertical-jump improvement. 17 studies, 317 people.
→ Zawieja et al., J Sports Sci 2024 · PMID 39514262
Homocysteine
−1.2 µmol/L
At ≥4 g/day, betaine reliably lowers blood homocysteine (5–20% at 6 g/day). It's one of the most consistent things betaine does.
→ McRae, J Chiropr Med 2013 · PMID 23997720
The cholesterol catch
↑ Total / LDL
That same 4 g+ dose can raise total and LDL cholesterol — documented in metabolic-syndrome subjects (not at 3 g/day or in healthy people). A real trade-off.
→ EFSA safety review · novel-food opinion
Power, sprint, endurance
No effect
The same meta found no significant benefit for upper-body strength, cycling-sprint power, bench-press-throw power, or muscular endurance.
→ Zawieja et al., 2024 · PMID 39514262
The Catches Worth Knowing
PubMed
Betaine is marketed for more than it can deliver. Three things to keep straight before believing the label.
The homocysteine trap
A number, not an outcome
Unproven
Lowering homocysteine looks healthy, but — like niacin and HDL — trials lowering homocysteine (mostly with B-vitamins) generally failed to cut heart attacks or strokes. A better number isn't a better outcome.
"TMG for mood / methylation"
Mostly theoretical
Thin
As a methyl donor, TMG feeds the SAMe pathway, which fuels mood and "methylation" claims. The mechanism is real; robust human trials for mood are not. Treat it as a hypothesis.
The FDA-approved use
A rare genetic disease
Homocystinuria
Betaine is an FDA-approved drug (Cystadane) — but only for homocystinuria, a rare inherited disorder. That approval isn't an endorsement for general "health" use.
The Evidence Table
PubMed
The honest ledger — the performance meta, the homocysteine meta, and the safety review.
| # | Study / Source | Type | What it found |
|---|---|---|---|
| 1 | Chronic betaine & exercise performance |
Meta-analysis 17 studies, 317 |
Modest (strength) |
| 2 | Betaine & plasma homocysteine |
Meta-analysis 5 RCTs |
Lowers it |
| 3 | Betaine safety (raises LDL at high dose) |
Safety review | Caveat |
| 4 | 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) that may not actually buy you better health — and can nudge LDL up at the higher doses. A reasonable add-on for a lifter; not a must-have, and not the methylation cure-all it's marketed as.
Cost & Sources
Market data
Cheap in powder form, and genuinely free in your food. Approx. U.S. prices.
Free
Food (beets, spinach, wheat)
$0
extra — "betaine" literally means "from beets"
Whole-food baseline
Prescription
Cystadane (homocystinuria Rx)
$$$
medical use only
For a genetic disease, not general health
Dosing Reality
Clinical / Research
The lifting dose and the homocysteine dose are different — and the higher one is where the cholesterol trade-off appears.
Strength / gym
2.5 g/day
The dose used in most performance studies; below the LDL-raising range
Homocysteine
4–6 g/day
Needed to move homocysteine — but this is where LDL can creep up
Upper limit
~6 g/day
Likely safe up to here; above it, GI upset and body odor (trimethylamine) appear
Watch
Your lipid panel
If you use the higher dose, it's reasonable to check cholesterol — especially with metabolic syndrome
Legal & Regulatory Position
T1 · Regulatory
Betaine is both a food component, a supplement, and — in one narrow case — an approved drug.
FDA
Supplement + a niche drug
Sold freely as a supplement; also approved as the prescription drug Cystadane for homocystinuria, a rare genetic disorder. The drug approval doesn't cover general "health" claims.
EFSA (Europe)
Safe with a cholesterol caveat
Europe assessed betaine as a novel food and flagged that intakes above ~4 g/day can raise total and LDL cholesterol — the basis for keeping doses moderate.
Sport (WADA)
Not banned
Betaine isn't on the prohibited list. As always with blends/pre-workouts, the risk is contamination — choose third-party-tested products.
What the Community Reports
Anecdotal
This section is anecdotal. Community reports — not controlled, not weighed as evidence.
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.
Longevity / methylation crowd
Paired with NMN
TMG is popular alongside NMN/NR to "support methylation." Reasonable theory; the human longevity evidence for TMG itself is thin.
High-dose users
"Fishy" smell
At large doses some report a fishy body odor (trimethylamine) and GI upset — the practical ceiling for most people.
→ Examine
Side Effects & Who Should Be Careful
Safety
Mostly easy-going, with one real catch most labels won't mention.
Common side effects
Gut & odor
Nausea, stomach upset, or diarrhea, mostly above ~6 g/day. At high doses some people get a faint fishy body odor (trimethylamine). Likely safe up to ~6 g/day.
→ RxList
Take too much →
↑ LDL cholesterol
The catch nobody mentions: doses above 4 g/day can raise total & LDL cholesterol — documented especially in people with metabolic syndrome. The gym dose (~2.5 g) stays below that.
Ask your doctor first if…
Watch lipids
You have high cholesterol or metabolic syndrome (check your lipid panel if using the higher homocysteine dose), kidney issues, or you're pregnant/nursing.
→ Examine
The honest safety bottom line: at the lifting dose (~2.5 g/day) betaine is cheap and safe. The one thing to watch is cholesterol if you go to the higher 4–6 g homocysteine dose — check a lipid panel, especially with metabolic syndrome.
The Bottom Line — In Plain English
What it is
Betaine (a.k.a. TMG, trimethylglycine) is a compound originally from beets. Your body uses it to recycle homocysteine and to donate "methyl groups."
What the research shows
A modest, real boost to lower-body strength, and it reliably lowers homocysteine. Little to nothing for power, endurance, or (proven) mood.
How it's used
~2.5 g/day for the gym; 4–6 g for homocysteine. Cheap, and also free in beets, spinach, and whole wheat.
Legality & safety
Legal supplement (and a niche Rx drug). Safe to ~6 g/day, but doses over 4 g can raise LDL cholesterol. Not banned in sport.
The honest verdict
A fine, cheap add-on for a lifter at ~2.5 g. Be skeptical of the "methylation/longevity" pitch — and if you go high-dose, watch your cholesterol.
- Betaine gives a modest, real boost to lower-body strength (and vertical jump) — but not to power, sprinting, or endurance.
- It reliably lowers homocysteine, but lowering homocysteine hasn't been shown to prevent heart attacks — a better number, not a proven benefit.
- The catch: doses above ~4 g/day can raise LDL cholesterol, especially in people with metabolic syndrome.
- "TMG for mood/methylation" is a reasonable theory with thin human evidence; don't pay a premium for it.
- It's cheap (~$0.15/serving), safe to ~6 g/day, and free in beets and spinach — a nice-to-have, not a must-have.