Beta-alanine under the microscope: a deceptively simple molecule with outsized physiological importance. β-alanine (3-aminopropanoic acid) is a naturally occurring non-proteinogenic amino acid, meaning it is not incorporated directly into proteins during translation like α-amino acids. Instead, its primary significance in human physiology comes from its role as the rate-limiting precursor to carnosine synthesis in skeletal muscle. Carnosine is a dipeptide formed from β-alanine and L-histidine through the action of carnosine synthase. Intramuscular carnosine concentrations are especially relevant during high-intensity anaerobic exercise because carnosine acts as an intracellular proton buffer. During repeated maximal efforts, glycolytic metabolism increases hydrogen ion accumulation, lowering pH and contributing to muscular fatigue. Elevated carnosine concentrations help attenuate this acidosis, delaying fatigue onset and sustaining force output. This is why beta-alanine supplementat...