COGNITION

Rae, C., Digney, A. L., McEwan, S. R., Bates, T. C. (2003). Proceedings of the Royal Society B: Biological Sciences, 270(1529), 2147-2150.

Classic double-blind, placebo-controlled crossover trial in 45 young adult vegetarians, deliberately chosen because they get little to no dietary creatine and tend to run lower baseline stores than meat-eaters. 5g/day of creatine significantly improved both working memory (backward digit span) and fluid intelligence (Raven's Advanced Progressive Matrices) versus placebo. One of the foundational studies behind the idea that creatine's cognitive benefit may show up most clearly in people starting from lower creatine stores, not universally.

Gordji-Nejad, A., Matusch, A., Hengstler, L., et al. (2026). Nutrients, 18(8), 1192.

29 healthy adults underwent 21 hours of continuous sleep deprivation, given a single dose of creatine monohydrate (0.2g/kg, ~14g) or placebo partway through. Creatine meaningfully reduced sleep-deprivation-induced decline versus placebo: logic tasks improved 6.1%, numeric ability 6.2%, language processing speed 12.3%, and psychomotor vigilance (reaction-time consistency) 9.2%, with women showing larger improvements than men on several measures. A single acute dose, not chronic daily supplementation, suggesting a real effect during a genuine energy-crisis state (sleep deprivation taxes brain ATP), not necessarily in a well-rested brain.

Xu, C., Bi, S., Zhang, W., Luo, L. (2024). Frontiers in Nutrition, 11, 1424972.

Meta-analysis of 16 RCTs (492 participants, ages 20.8-76.4) found creatine supplementation significantly improved memory and processing speed, but found no significant effect on overall cognitive function or executive function. Benefits were larger in people with a diagnosed disease versus healthy people, and larger in women than men for processing speed. Sounds like a strong positive result, but see the entry below, a real methodological problem was found in how this meta-analysis pooled its data, and it deserves real weight in how much confidence to place in these numbers.

Citherlet, T. (2026). Frontiers in Nutrition, 13, 1716285.

A direct methodological critique of the Xu et al. 2024 meta-analysis above. Several of the pooled studies contributed multiple correlated test scores from the same participants (e.g. one study contributed 7 memory subtests, others 4 each) treated as if they were independent observations, which artificially inflates the apparent sample size and overstates statistical confidence. The European Food Safety Authority's own 2024 review flagged this same problem and concluded no reliable conclusions could be drawn from that data. A prior instance of the identical error in a different creatine-memory meta-analysis, once corrected, saw its "significant" effect disappear except in older adults. A real citation-accuracy lesson: an exciting-looking meta-analysis result deserves scrutiny of its pooling method, not just its headline finding.

Molloy, G., Somani, Y., Delvenne, J. F., Burke, M. (2026). Ageing Research Reviews, 121, 103277.

PRISMA-guided, PROSPERO-registered systematic review and meta-analysis of multi-session resistance exercise programs in healthy adults (not limited to older adults), organizing outcomes under the Cattell-Horn-Carroll cognitive ability framework. Found resistance exercise improved global cognition, executive function, working memory, and processing speed, but episodic memory retrieval showed no consistent benefit and varied substantially across the pooled studies. The authors frame the effect as domain-specific rather than a uniform brain boost, and flag real heterogeneity across studies in training duration, intensity, and how cognition was measured as reasons to stay cautious about the strength of these findings. Specific effect sizes and study count aren't available in the public abstract, the full paper sits behind an Elsevier paywall.

Jorquera-Caceres, I., Salazar-Mendez, J., Arnal-Gomez, A., Espi-Lopez, G. V., Alvarado-Araya, P. (2026). Journal of the American Medical Directors Association, 27(10), 106427.

Meta-analysis of 17 trials in community-dwelling adults 60 and older with no cognitive impairment. Resistance training significantly improved working memory (SMD 0.30, 95% CI 0.02-0.59, p=.04) and cognitive flexibility (SMD -0.50, 95% CI -0.88 to -0.12, p=.009, negative value favors resistance training on this measure), but had no significant effect on inhibitory control. When resistance training was compared head-to-head against other exercise types rather than against no exercise, none of the three domains showed a significant difference, meaning resistance training isn't shown here to be uniquely better than other exercise for cognition, just better than not exercising. Authors explicitly caution the evidence carries low certainty given high risk of bias and inconsistent protocols across the pooled trials.