Also known as: GAA, Glycocyamine, Creatine precursor
Performance & PowerEmerging evidence
The compound your body makes creatine from. It raises muscle creatine more effectively than creatine itself in some people, at the cost of a methylation load that needs managing.
Typical dose
1.2–3.0 g per day
Daily, with betaine or B vitamins
What it is
Guanidinoacetic acid is the direct precursor to creatine. Your body makes it in the kidneys from glycine and arginine, then the liver adds a methyl group to convert it into creatine.
Supplementing GAA supplies that precursor and lets your own metabolism complete the final step.
The interesting group is creatine non-responders, roughly 20 to 30 per cent of people whose muscle creatine barely rises on monohydrate. GAA appears to work through a different route and has raised muscle creatine in some of them.
How it works
GAA is taken up by tissues and methylated to creatine, using a methyl group donated by S-adenosylmethionine.
That methylation step is the key to both its advantage and its drawback. Because GAA uses a different transporter from creatine, it can bypass the transporter saturation that limits response in non-responders.
The cost is that each conversion consumes a methyl group, which raises homocysteine. That is a manageable and well-understood consequence rather than a mystery, and it is why GAA is generally taken with betaine or B vitamins.
What the evidence shows
Human trials have shown that GAA raises muscle and blood creatine, in some studies more effectively than an equivalent dose of creatine monohydrate over several weeks.
Research has also confirmed the homocysteine rise, and shown that co-supplementing with betaine or B vitamins substantially reduces it.
Performance trials are fewer than the biochemical ones, so raising muscle creatine is better demonstrated than any resulting change in what you can lift. GAA also lacks novel food authorisation in some markets, which limits availability.
Dosing
Trials have used 1.2 to 3 g daily over four to eight weeks. Higher doses raise homocysteine more, so starting at the lower end is sensible.
Take it with betaine at 2 to 3 g, or with adequate B6, B12 and folate. This is not an optional refinement, since the methyl group consumption is the main downside and it is straightforward to offset.
Monohydrate remains the first choice for most people: cheaper, better evidenced, and without the methylation consideration. GAA is worth considering if you have used monohydrate properly for a month and seen nothing.
At a glance
Common forms
Guanidinoacetic acid powder, Combined with betaine, Creatine monohydrate (first-line alternative)
Half-life / duration
Muscle creatine rises over 4-8 weeks
Timing
Daily, with betaine or B vitamins
Competition status
Permitted — not on the WADA Prohibited List
Category
Performance & Power
Safety and side effects
GAA has been reasonably well tolerated in trials, with digestive upset and occasional skin flushing reported.
The homocysteine rise is the main documented consideration, and it is dose-dependent and reduced by taking betaine or B vitamins alongside.
Long-term data is limited compared with creatine monohydrate. Speak to your doctor before use if you take regular medication, or if you have been advised to watch your homocysteine.
Who should avoid it
Take alongside betaine or adequate B6, B12 and folate to offset the rise in homocysteine. Speak to your doctor before use if you have been advised to watch your homocysteine, or if you take regular medication. Long-term data is limited. Availability may be restricted in some markets. Not established in pregnancy or breastfeeding.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
