CREATINE, CANCER AND THE METASTASIS QUESTION · What the new evidence really changes - and what it does not

A widely used sports supplement is now linked to platelet biology and metastasis in experimental cancer models. That does not mean creatine causes cancer. But dismissing the finding simply because most of the evidence comes from mice would be equally unscientific. Preclinical evidence now supports a biologically plausible pro-metastatic role for high creatine availability in selected tumour and host-cell contexts. Human evidence, however, does not currently demonstrate that routine creatine supplementation increases cancer incidence, metastatic recurrence or cancer mortality. Creatine occupies an unusual position in modern nutrition. It is inexpensive, naturally present in the human body, found in ordinary foods such as meat and fish, supported by decades of sports-performance research, and consumed every day by competitive athletes, recreational gym users, older adults and people interested in healthy ageing. It is therefore understandable that a headline linking creatine with cancer attracts attention. On 1 October 2026, the Spanish broadcaster Cadena SER discussed a recent study and asked whether creatine supplements might stimulate tumour cells. The report highlighted a genuine scientific signal, but public discussion quickly began to blur four very different questions: whether creatine causes cancer, whether it feeds cancer cells, whether it can promote metastasis, and whether experimental exposures resemble common supplementation practices. Those questions are not interchangeable. Creatine is not a protein, an anabolic steroid or a mutagen. More importantly, carcinogenesis, primary-tumour growth and metastasis are biologically distinct processes. A factor may influence one without causing another. The July 2026 study by Xie and colleagues in Nature Communications deserves serious attention because it identifies a previously unrecognised route through which exogenous creatine can alter megakaryocyte metabolism, increase platelet reactivity and facilitate metastasis in several experimental cancer models [1]. It also reports a small human mechanistic experiment in which 20 g/day of creatine monohydrate for 14 days increased platelet reactivity in healthy volunteers. What it does not provide is evidence that those volunteers developed cancer, metastatic disease or any oncological outcome. The scientifically useful question is therefore not “Does creatine cause cancer?” but rather: Could increasing systemic creatine availability alter the behaviour of an existing tumour - particularly its ability to disseminate - in certain biological contexts? Preclinically, the answer is yes. Clinically in humans, we do not yet know.