What does creatine actually do? The evidence, weighed

Creatine is a compound the body makes and uses to regenerate energy for short, intense efforts, and the evidence for its performance effect is among the strongest in sports nutrition: a 2022 International Society of Sports Nutrition position stand, reviewing hundreds of trials, concluded creatine monohydrate supplementation increases strength, sprint performance, and fat-free mass in combination with training. The effects are modest and population-dependent — measured in single-digit percentages — and the evidence for newer claims around cognition and recovery is thinner. This is information, not medical advice; personal decisions belong with a qualified clinician.

What follows weighs the evidence claim by claim — what the studies show, in whom, and what they do not.

Does creatine improve strength and power?

Yes, with one of the larger evidence bases in the field. A 2022 meta-analysis of 35 randomized trials in adults found supplementation combined with resistance training increased maximum strength (typically measured as one-repetition maximum) by several percent over training alone, with similar direction in younger and older adults. The mechanism is documented: more phosphocreatine in muscle means faster regeneration of ATP — the cell's energy currency — during short bursts. The effect appears in trained and untrained populations; absolute gains vary by responder status, a known individual difference the ISSA position stand acknowledges.

Does creatine cause weight gain?

Water weight, mostly, and quickly. Trials consistently show an initial one-to-two-kilogram increase in body mass in the first weeks, attributed to intramuscular water retention, per the 2022 ISSN position stand's summary of body-composition studies. Longer-term increases in fat-free mass accompany training effects and are part of the strength finding above. The water weight is not fat mass — body-composition studies distinguish them — but it is real scale weight, which matters to athletes in weight classes.

Does creatine help the brain?

The evidence is early and mixed. Small trials — typically under 50 participants — have tested creatine in sleep-deprived adults and older adults, with some showing modest improvements in memory and reaction-time tasks and others showing none; a 2023 systematic review of cognitive studies characterized the evidence as promising but inconsistent, with vegetarian populations (whose baseline intake is lower) showing the clearest effects. No large, replicated trial exists. This is a "possibly, in some populations, unproven" finding, stated as such.

Is creatine safe?

The short- and medium-term safety record in healthy adults is well documented: the ISSN position stand and a substantial trial literature report no adverse effects on kidney function in healthy people at studied amounts. The caveats are specific: people with existing kidney disease were largely excluded from the trials, and the US National Institutes of Health's dietary-supplement fact sheet advises such individuals to consult a clinician. A separate documented point: supplements as a category are regulated differently from drugs in the US — not pre-approved for safety or efficacy by the FDA — so product quality varies between brands; third-party certification programs exist and are the standard workaround, per NIH's guidance.

What form works — do the newer versions matter?

Monohydrate carries nearly all the evidence. The 2022 position stand compares forms directly: alternatives — hydrochloride, buffered, liquid — lack equivalence testing, and several head-to-head trials found no advantage over monohydrate, which is also the cheapest and most-studied form. The comparison table:

The table reports what the studies found, not a purchase recommendation; brand and product choices are individual ones.

What does the evidence not show?

Four claims without support equal to their marketing. Endurance performance: creatine's mechanism is short-duration energy; trials show no benefit for long-duration aerobic work. Weight loss: no good evidence; the scale moves the other way initially. Hair loss: a single small 2009 study of rugby players reported an association, never replicated, per the ISSN's review of the safety literature. And "loading phases" as a necessity: they accelerate saturation but are not required, per the position stand — a fact about schedules, not a protocol recommendation. What the record supports: a modest, reliable strength and power effect, a good safety record in healthy adults, and an evidence frontier beyond muscle that remains open.