Creatine
Evidence: moderate
Strong for power and for the gym work that supports running; mixed for steady endurance. Watch the water-weight gain, which penalises weight-bearing running.
Not medical advice
This is a general knowledge base, not medical or dietary advice. If you are injured, unwell or weighing up a supplement or a change to your diet, speak to a doctor, physiotherapist or registered dietitian who knows your situation.
Creatine is one of the best-evidenced supplements in sport overall, classed Group A, but its case for distance running specifically is mixed rather than strong (Forbes et al. 2023). The evidence is robust for sprint and power performance and limited or null for steady-state endurance, where a meta-analysis found no benefit in trained individuals.
The complication for runners is body mass. Creatine draws water into muscle, adding roughly 0.9 to 2 kg, which penalises weight-bearing endurance; one early study found impaired 6 km running after loading (Forbes et al. 2023). For this reason runners are advised to skip the rapid loading phase and take 3 to 5 g per day over about four weeks, avoiding the acute water-weight spike.
There are plausible upsides for distance runners at the margins: end-spurts and repeated high-intensity intervals, enhanced glycogen storage when taken with carbohydrate, and reduced post-race inflammatory and muscle-damage markers, suggesting a recovery role (Forbes et al. 2023). These are moderate-to-limited in strength, and the data specific to female and masters runners are sparse.
The strength-training case
Creatine’s strongest and best-evidenced effect is on resistance training, and this is the most relevant angle for runners, because most runners benefit from concurrent strength work. It reliably increases strength, power and lean mass gains from resistance training, by allowing higher-quality sessions through faster phosphocreatine resynthesis between sets (Forbes et al. 2023). Since strength training improves running economy without adding race weight, a runner who lifts to support their running has a coherent reason to take creatine: not for its direct endurance effect, which is weak, but to get more out of the gym work that does help. The water-weight gain still applies, so it is a clearer fit in a strength-focused base phase than in the final weeks before a race.
The reasonable overall reading: not a core endurance aid, but a defensible choice for runners who also lift, want the recovery benefits, and can accept the weight gain.