Betaine for Athletes: Benefits and the Evidence Behind Them
Betaine, also called trimethylglycine or TMG, began life in sports nutrition as a little-known ingredient in pre-workout formulas. Over the past fifteen years a modest body of research has grown around it, with claims ranging from more reps to better body composition. Our editorial team reviewed what is supported, what is preliminary and how to use it sensibly.
What betaine is and where it comes from
Betaine is a small molecule made of the amino acid glycine with three methyl groups attached. It was first identified in sugar beets, which is where the name comes from. Today most supplemental betaine is extracted from beet processing byproducts.
It occurs naturally in foods such as wheat bran, wheat germ, spinach, quinoa, beets and shellfish. Craig's 2004 review in the American Journal of Clinical Nutrition estimated typical dietary intakes in the range of roughly 100 to 300 mg per day, varying widely with diet. The body also produces betaine from choline.
Betaine has two well-established roles. It is an osmolyte, helping cells retain water and maintain volume under stress, and it is a methyl donor, supplying methyl groups that convert homocysteine back into methionine in the liver and kidneys.
In medicine, anhydrous betaine is an FDA-approved prescription treatment for homocystinuria, a rare inherited disorder. As a sports supplement, it is sold under DSHEA rules at much lower doses and without pre-market review.
How it might work in muscle
The osmolyte function is the first proposed mechanism. Under the dehydration and heat stress of intense exercise, keeping cells hydrated may protect proteins and support contraction. This is similar in spirit to how creatine increases cell volume, although the evidence base is far smaller.
The methyl donor role may also matter. Methylation reactions support creatine synthesis in the body; some researchers have suggested that betaine could spare methyl groups and indirectly support muscle creatine. Direct evidence for a meaningful effect in athletes is lacking.
Some studies have measured hormonal and signaling changes, such as small increases in markers of anabolic signaling or growth hormone after betaine supplementation. These observations are interesting but inconsistent and come from small groups.
Cholewa and colleagues (2013) also proposed that betaine might reduce homocysteine thiolactone, a compound that could impair protein synthesis. This hypothesis remains largely theoretical in humans.
Strength, power and endurance trials
Results in strength and power are mixed but lean slightly positive. Lee and colleagues (2010) reported improved power output in some upper and lower body exercises after two weeks of 2.5 grams per day. Hoffman and colleagues (2009) found improvements in the number of squat repetitions and in the quality of repetitions, while other measures did not change.
Trepanowski and colleagues (2011), on the other hand, found that betaine improved volume in some sets but not others, and did not consistently improve power. Several studies report no effect on one-repetition maximum strength.
For endurance, evidence is very limited. A few small trials in cyclists and runners, often in hot conditions, produced inconsistent results. There is no strong basis for recommending betaine to endurance athletes at this time.
Overall, betaine seems to have, at best, a small effect on training volume and power in some people. It is not in the same evidence category as creatine, caffeine or beta-alanine. The IOC consensus statement on supplements does not list it among those with good evidence.
Body composition and homocysteine
The study that drew most attention was a 2013 trial by Cholewa and colleagues. Trained men taking 2.5 grams of betaine per day during six weeks of resistance training showed improved body composition, with more lean mass and less fat, compared with placebo. Arm cross-sectional area also improved.
Not all trials confirm this. Schwab and colleagues (2002) gave 6 grams per day to obese adults for 12 weeks with a hypocaloric diet and found no effect on body weight, body composition or resting energy expenditure. Context, dose and training status may explain some differences.
The homocysteine effect is the most consistent finding. Olthof and colleagues (2003) showed that even low doses of betaine lower plasma homocysteine in healthy adults. Elevated homocysteine is a marker associated with cardiovascular risk, although lowering it with supplements has not been shown to reduce cardiovascular events in large trials.
| Claim | Evidence strength | Comment |
|---|---|---|
| Lowers homocysteine | Good | Consistent across trials; clinical relevance uncertain |
| Increases training volume | Moderate to weak | Small, inconsistent effects |
| Improves body composition | Weak | A few positive trials, others null |
| Increases maximal strength | Weak | Most studies show no change |
Dosing, safety and product quality
Most sports studies used about 2.5 grams per day, often split into two doses of 1.25 grams, for one to six weeks. This amount can also be found in some pre-workout formulas, although many products contain far less than research doses.
- Typical studied dose: 2.5 g per day, divided into 1–2 servings.
- Timing: daily intake matters more than precise timing; with meals is convenient.
- Duration: trials lasted mostly 2–6 weeks; long-term athletic data are sparse.
At these doses, betaine appears well tolerated. Some people report mild nausea, diarrhea or a fishy body odor at higher intakes. That odor occurs because betaine can be metabolized to trimethylamine in a small number of people.
A notable concern is blood lipids. Some studies, including work by Schwab and colleagues, observed increases in LDL cholesterol with higher doses, roughly 4 grams per day or more. People with high cholesterol or cardiovascular disease should discuss betaine with a doctor before using it.
Betaine HCl, sold as a digestive aid, is a different product with added hydrochloric acid and is not intended for sports performance. Athletes should also choose third-party tested products, as pre-workouts containing betaine sometimes include undeclared stimulants.
The Editorial Team's Conclusions
Betaine is a safe, inexpensive supplement with a small amount of research suggesting modest gains in training volume and power, and possibly body composition.
The evidence is inconsistent, and betaine should not be considered a core supplement. Training, nutrition and well-established supplements deliver far more.
If you want to try it, 2.5 grams per day is the studied amount. People with high LDL cholesterol should be cautious with higher doses.
Related reading on our site includes reviews of creatine monohydrate, of citrulline malate for strength training, and of how to evaluate pre-workout labels.
References
- Cholewa JM, Wyszczelska-Rokiel M, Glowacki R, et al. Effects of betaine on body composition, performance, and homocysteine thiolactone. J Int Soc Sports Nutr. 2013;10(1):39.
- Lee EC, Maresh CM, Kraemer WJ, et al. Ergogenic effects of betaine supplementation on strength and power performance. J Int Soc Sports Nutr. 2010;7:27.
- Hoffman JR, Ratamess NA, Kang J, et al. Effect of betaine supplementation on power performance and fatigue. J Int Soc Sports Nutr. 2009;6:7.
- Trepanowski JF, Farney TM, McCarthy CG, et al. The effects of chronic betaine supplementation on exercise performance, skeletal muscle oxygen saturation and associated biochemical parameters in resistance trained men. J Strength Cond Res. 2011;25(12):3461–3471.
- Craig SA. Betaine in human nutrition. Am J Clin Nutr. 2004;80(3):539–549.
- Olthof MR, van Vliet T, Boelsma E, Verhoef P. Low dose betaine supplementation leads to immediate and long term lowering of plasma homocysteine in healthy men and women. J Nutr. 2003;133(12):4135–4138.
- Schwab U, Törrönen A, Toppinen L, et al. Betaine supplementation decreases plasma homocysteine concentrations but does not affect body weight, body composition, or resting energy expenditure in human subjects. Am J Clin Nutr. 2002;76(5):961–967.
