A dipeptide protein of two amino acids (histidine and beta-alanine) produced naturally in the body. Carnosine is highly concentrated in the muscles (when under tension) and brain, but it also used by the heart, liver, and kidneys.  It is believed to contribute significantly to muscle strength, muscle power, endurance, muscle growth, and possibly even fat loss.

During exercise, muscle acidity increases due to the production of lactic acid. As the muscles become more acidic, their ability to contract and produce power decreases. Large amounts of carnosine in the muscle fibers helps delay the production of lactic acid, thereby increasing the amount of time before a muscle becomes tired.

A synthetic form or carnosine is often sold as an anti-aging supplement.