Two grams a day. That was the entire dose of guanidinoacetic acid (GAA) taken by volunteers in a new six-week trial, and it coincided with faster reaction times on some memory tasks.
The catch is that most of the brain tests showed nothing at all. The authors themselves call the study exploratory, and the details matter more than the headline.
What GAA actually is
GAA is the direct metabolic precursor of creatine. The body makes it from the amino acids arginine and glycine, then converts it to creatine by adding a methyl group.
Supplement makers pitch GAA as a more efficient route to the same end product, effective at a fraction of the usual creatine dose. The trial’s background notes that GAA has been reported to raise brain creatine content more effectively than creatine monohydrate (CrM), though whether that translates into better thinking has been unclear.
That question matters because the brain is an energy-hungry organ, and creatine helps buffer the cellular fuel it runs on. If GAA lifts brain creatine further than creatine itself, it is a plausible candidate for a cognitive edge. Plausible is not the same as proven.
How the trial was built
The work comes from the Exercise & Sport Nutrition Lab at Texas A&M University, with Jisun Chun as first author and Richard Kreider, a professor in the department of kinesiology and sports management, as senior author. It was published in the Journal of the International Society of Sports Nutrition and registered as ISRCTN68542582.
The study was double-blind and randomized, with 58 healthy, active adults (33 of them women, average age 35.5). Each participant took one of three regimens for six weeks: a maltodextrin placebo (12 g a day), GAA at 2 g a day plus placebo, or GAA at 2 g a day plus 10 g of creatine monohydrate.
Participants gave fasting blood samples and completed a battery of cognitive tests and questionnaires on mood, stress, sleep and quality of life, at baseline and again after six weeks. The authors describe it as a proof-of-concept trial, which is a polite way of saying it was designed to generate leads rather than settle arguments.
The reaction-time signal
The most interesting result was speed. GAA alone tended to improve overall reaction time by 241.8 milliseconds (95% confidence interval: -533 to 50 ms, p = 0.10), which did not cross the study’s threshold for significance.
The analysis of how groups changed over time relative to placebo was firmer. It showed a significant interaction effect for overall reaction time (-330 ms, 95% CI -629 to -31, p = 0.031) and for reaction time on YES responses (-290 ms, 95% CI -484 to -96, p = 0.004).
Two related measures, reaction time on correctly recalled items and the percentage of correct YES recalls, approached significance without reaching it (p = 0.078 and p = 0.084). Based on this pattern, the authors concluded that supplementation improved delayed verbal episodic recognition memory and retrieval speed.
Note the width of those confidence intervals. An interval running from -629 to -31 ms is compatible with a very large effect or a barely detectable one. That is common in a study this size, and it is why one significant p-value does not make a finding.
Where nothing happened
Four other cognitive tests told a much quieter story. The Delayed Picture Recognition Task, Digit Vigilance Task, Corsi Block Task and Stroop Color-Word Task showed limited to no effects.
Those tests cover visual memory, sustained attention, spatial working memory and the ability to override an automatic response. In other words, GAA did not lift the broad range of mental skills that a “brain supplement” is usually sold on.
The authors say as much. Most cognitive tests were unaffected, particularly when GAA was compared directly with placebo, and the results contained inconsistencies. Their own conclusion is that more research is needed before anything can be concluded.
Stress, sleep and how people felt
The secondary outcomes were a mixed bag. Time spent in moderate physical activity was significantly greater in the GAA group than in the placebo group (p < 0.05), which is interesting but could reflect anything from motivation to seasonal habits.
On the Perceived Stress Scale, the GAA group reported a lower frequency of controlling irritations (p = 0.036) and a borderline signal on feeling that difficulties were mounting (p = 0.053). The sleep data showed what the authors call positive and potentially undesirable effects, without a clean direction.
The quality-of-life questionnaire added more scattered signals. The GAA group reported feeling less worn out (p = 0.068), while the GAA plus creatine group reported feeling more full of life (p = 0.081) and less downhearted and depressed (p = 0.066), but also more limitation when bending, kneeling or stooping (p = 0.053).
Most of those values sit above the conventional 0.05 line. When a trial measures dozens of questionnaire items, a few will land near the threshold by chance alone, so these results are best read as hypotheses for a larger study.
What the blood work showed
Safety is where the trial gave its clearest answer. The researchers found no clinically meaningful changes in blood markers and no meaningful differences in self-reported side effects between groups.
That is reassuring for a six-week window, but it is not a long-term safety verdict. Because the body uses methyl groups to convert GAA into creatine, researchers routinely watch metabolic markers tied to that process in GAA studies, and longer trials will be needed to say more.
What this means for creatine users
The design has an important limit. There was no arm taking creatine monohydrate alone, so the study cannot say whether GAA beats creatine, or whether adding GAA to creatine does anything that creatine would not do by itself.
Creatine monohydrate remains the supplement with the deepest evidence base in sports nutrition, and readers weighing it can start with the Athletic Insight creatine guide. This trial does not change that picture.
What it does is open a door. A precursor taken at 2 g a day produced a handful of reaction-time and memory-retrieval signals in healthy adults without obvious harm, which is enough to justify a larger, preregistered trial with a creatine-only comparison.
Until that trial exists, the honest reading is narrow: one promising cluster of results, several null ones, and a supplement whose brain benefits are still a question rather than an answer.
