Betaine (TMG; trimethylglycine. A glycine amino acid with three methyl groups) is a bodybuilding supplement usually found in pre-workouts to boost muscle growth. Betaine is also used to improve digestion, fight infections, and for methylation support.
Due to its ability to support methylation (converts homocysteine to methionine), it has a methionine “sparing effect” and might aid in nitrogen retention and muscle growth. Methionine is used to create polyamines (which is needed for recovery and growth), creatine and phosphatidylcholine just to name a few.
An elevation in phosphatidylcholine concentration may have potential ergogenic implications for athletic performance. Considering that choline intake is important for enhancing neurotransmitter concentration, the ability to enhance strength, power, or ability to react to external stimuli could be enhanced with greater neurotransmitter formation. Phosphatidylcholine can also be converted to phosphatic acid, which has an anabolic effect (1).
Betaine is also an osmolyte, which maintains adequate cellular hydration. This helps with proper energy production, muscle protein synthesis, DNA replication, etc. If the cell becomes too dehydrated, muscle protein synthesis stops and muscle protein breakdown is increased.
- Improves cellular hydration. Other osmolytes are taurine, inositol, and creatine. Insulin, glycine and glutamine are also able to increase cellular hydration and prevent cellular dehydration. Properly hydrated cells are able to:
- initiate hypertrophy
- inhibit protein catabolism
- Is metabolized to glycine when it has donated its methyl donors. Glycine is an anabolic, anti-catabolic, anti-inflammatory and androgenic amino acid (A).
- Lowers homocysteine, which inhibits muscle protein synthesis, is inflammatory and promotes disease.
- Increases growth hormone (GH) and insulin-like growth factor-1 (IGF-1) and lowers cortisol (2).
- Has been thought to increase creatine, but doesn’t increase creatine phosphate (3).
- Has been thought to increase nitric oxide, but doesn’t (4).
- Increase synthesis of phospholipids.
So how useful is it really? Let’s look at a few studies.
Betaine supplementation increases total repetitions and total volume load by approximately 6.5% on the bench press (5).
In another study, they also found an increase in bench press reps, lower lactate, greater muscle tissue oxygen saturation and consumption. The enhancement of performance was similar to beta-alanine and caffeine supplementation. However, the betaine group was eating 400 more calories, which indicates that it wasn’t the betaine that had the ergogenic effect (6).
In two other studies (7, 8) where food intake wasn’t controlled, betaine supplementation (1.25g twice daily) increased power, force and maintenance of these measures in selected performance measures, and these were more apparent in the smaller upper-body muscle groups. However, there were no differences in jump squat power or the number of bench press or squat repetitions. Blood lactate was the same and body weight didn’t change between groups, however, the study was only 14 days long.
In a more controlled study, where both the betaine (1.25g twice a day) and placebo group ate the same amount of food (2639 ± 790 kcal, 143.2 ± 70.7 g total protein, 316 ± 109 g total carbohydrates, and 94.2 ± 41.7 g total fat), there wasn’t a difference in strength, power or endurance on the bench, but a small amount on the squat. Unfortunately, they didn’t measure hypertrophy (9).
In another small crossover design study, betaine (2.5g 60 min before workout) didn’t improve exercise performance but did reduce fatigue (10).
Strength & hypertrophy
Betaine increased arm size (the betaine group had less size, to begin with), but not leg size. Bench volume increased, but not squat volume. They experienced a decrease in fat mass (they were fatter to begin with) and an increase in lean mass (they had less lean mass to begin with) vs the placebo. However, food intake wasn’t controlled. Hypertrophy was tested via skin folds so the improvements could have been an increase in cellular water, as it’s not an accurate measure of hypertrophy. If weight increases by fluid retention, percent body fat will decrease even if total body fat does not change (11).
In this study (12), betaine supplementation didn’t improve fat loss while eating 1500 calories daily (18% protein, 27% fats and 52% carbs). However, they didn’t exercise, as exercise might have enhanced the benefits.
When compared to combined with creatine, betaine didn’t provide any benefit to improving strength, hypertrophy and reducing body fat on its own or in addition with creatine (13). The downsides to this study is that they used untrained men and that the study was only 10 days long. Not nearly enough time to see an improvement in strength, hypertrophy or fat loss.
Betaine might have a slight benefit to it, but it’s very small. There is a lack of controlled studies of longer duration on trained men. I would not be including this supplement into my own pre-workout, but rather use other ergogenic aids that are also osmolytes, such as creatine, glycine and taurine.
Betaine supplementation is actually able to lower taurine levels by inhibiting the enzyme CDO (cysteine dioxygenase), because homocysteine is converted to methionine, instead of taurine. Taurine is also an ergogenic substance with a lot more benefits than betaine (A). Rather focus on eating enough protein for your methionine and skip in the betaine.
If you still want to take it, 2.5g is the minimum required dose in increase betaine levels pre-workout, and it usually spikes between 40 and 60 minutes after ingestion. Betaine accumulates in the body similar to creatine, which might reduce the need for specific timing as well.