Creatine monohydrate

The verdict

Our read at a glance.

Whether the most-studied sports supplement does what it claims, and how large the effect really is.

The signal

The evidence base is unusually deep for this field: a large randomized literature and continuing registered trials across performance, ageing muscle, rehabilitation and clinical populations. The consistent findings are an increase in intramuscular phosphocreatine, improved performance in repeated high-intensity efforts, and a modest increase in lean mass, part of which is intracellular water rather than contractile tissue. The effect is real, replicated, and small in absolute terms - which is exactly why it is the right yardstick. It also has a growing literature in non-muscle contexts including cognition and neurological conditions, where the evidence is earlier and less settled.

The unknown

How much of the cognitive and clinical literature will hold up, and whether the subset of people who do not respond are non-responders for a characterisable reason.

Our read

Included deliberately as a reference point. This is what an evidence base looks like when a compound genuinely has one: hundreds of trials, an effect size small enough to be believable, safety data measured in decades, and no need to argue about legality. Any compound on this Watchlist promising ten times the effect on a tenth of the evidence should be read against this page.