Creatine vs protein — which supplement matters more?

These work through different mechanisms and aren't really substitutes for each other. Protein supplies the amino acids your body needs to actually build muscle tissue — a foundational meta-analysis and its many replications, including specifically in older adults with sarcopenia, confirm it meaningfully boosts resistance-training-induced strength and mass gains. Creatine works differently: it boosts the phosphocreatine energy system that fuels short, intense effort, which is why it consistently increases strength and power output in meta-analyses, again especially in older adults — plus a modest, independently-supported cognitive benefit protein doesn't share. Both have strong, well-replicated evidence. If you're only going to pick one, protein intake matters more broadly (you need it regardless of training goals); creatine is the more specific performance add-on on top of that.