Study
Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled, cross-over trial
In 45 young vegetarian adults, 5 g/day of creatine for 6 weeks improved both backward digit span and Raven's Advanced Progressive Matrices scores at p < 0.0001.
Caroline Rae and colleagues tested 45 young adult vegetarians in a double-blind, placebo-controlled, cross-over trial. The dose was 5 g/day of oral creatine monohydrate. The duration was six weeks per arm. Two outcomes were measured: working memory by backward digit span, and non-verbal intelligence by Raven's Advanced Progressive Matrices.
Creatine improved both. The reported effect on working memory and on intelligence was significant at p < 0.0001. The authors note that both tasks depend on speed of processing, and they attribute the result to increased brain energy capacity. Vegetarians were chosen deliberately because they consume little dietary creatine, so their baseline stores are lower than in omnivores and the headroom for a supplementation effect is larger.
This trial is the origin of the claim that creatine improves cognition, and it is cited by most later reviews on the topic. The published abstract reports the p-value only. No effect sizes, mean differences or confidence intervals are given, so the magnitude of the improvement cannot be read from the paper's abstract.
These findings underline a dynamic and significant role of brain energy capacity in influencing brain performance.
N = 45, small. Participants were young adult vegetarians with low baseline creatine intake, which is the population most likely to respond; the result does not transfer to omnivores or older adults without further evidence. Only two cognitive tests were used, both dependent on processing speed, so the finding is narrow. The abstract reports p < 0.0001 but no effect size, mean difference or confidence interval, so the practical size of the gain is unknown. A cross-over design of two six-week arms carries carry-over risk, since muscle and brain creatine take 4 to 6 weeks to return to baseline after supplementation stops; the abstract does not describe a washout period. Published in 2003; later meta-analyses (Xu 2024, Prokopidis 2023) found smaller and less consistent cognitive effects than this single trial suggests. No funding or conflict-of-interest statement was available on the pages fetched.
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