What is betaine?
Betaine, also called trimethylglycine (TMG), is a compound found in beetroot, wheat bran, and spinach. The body also makes it from choline. It is distinct from betaine HCl, which is sold as a digestive aid and serves a different purpose.
How it works
Betaine has two roles. As an osmolyte it helps regulate cellular fluid balance in a similar way to creatine, supporting hydration and cell volume during training. As a methyl donor it supports methylation reactions and helps lower homocysteine, a cardiovascular marker.
What the research says
- Several studies show improved power output and training volume at 2.5g per day
- Cholewa et al. (2013) reported improved body composition over six weeks of supplementation
- Effects on one-rep-max strength have been inconsistent across trials
- Reliably lowers homocysteine, independent of any training effect
Effective dose
2.5g per day, taken consistently. Benefits accumulate over weeks rather than acutely, so daily use matters more than timing it around a session. It can be taken alongside creatine.
What to check on the label
Look for betaine anhydrous or trimethylglycine (TMG) at around 2.5g. It is frequently underdosed in pre-workout blends. Do not confuse it with betaine HCl, which is intended for digestion, not performance.
Safety
Well tolerated at standard doses. Mild gastrointestinal upset can occur at higher intakes, and a fishy body odour is a rare side effect at very high doses.