Creatine Monohydrate — Amino acid derivative / phosphagen

Creatine is synthesized endogenously from arginine and glycine (liver, kidney) and obtained from dietary meat. Taken up by muscle and brain via SLC6A8 transporter and phosphorylated by creatine kinase to phosphocreatine (PCr), the primary buffer for ATP regeneration during high-intensity effort. Supplementation increases intramuscular PCr stores by ~20%, enhancing short-burst power output. Also promotes satellite cell activity, IGF-1 signaling, and myosin heavy chain expression. Emerging cognitive benefits: raises brain PCr stores (especially relevant in vegetarians/elderly); multiple RCTs show benefit on memory and fluid intelligence.