Carnosine

Carnosine, chemically beta-alanyl-L-histidine, is a dipeptide formed from the amino acids beta-alanine and L-histidine ^[1][4]. It was first isolated from meat extract by the Russian chemist Vladimir Gulevich around 1900, and its name derives from the Latin for flesh, reflecting that it is concentrated in animal tissue and is essentially absent from plants ^[4]. In the body it occurs at high, millimolar levels in skeletal muscle and, at lower concentrations, in the brain and other excitable tissues ^[2].

Several biochemical roles are attributed to carnosine. In muscle its best-established function is as an intracellular pH buffer: because one of its groups ionizes in the range of pH reached by working muscle, it soaks up the hydrogen ions produced during intense exercise and so helps delay the acidification that contributes to fatigue, accounting for a notable share of the muscle's buffering capacity ^[1][4]. It is also an antioxidant that neutralizes reactive oxygen species and, importantly, the reactive aldehydes generated when fats and sugars are oxidized; a related activity is its antiglycation effect, in which carnosine scavenges carbonyl compounds and reduces the formation of advanced glycation end-products implicated in diabetes and aging ^[1][3]. In addition it can chelate metal ions and appears to help regulate calcium handling in muscle ^[1][4].

The body makes carnosine from beta-alanine and histidine, and because beta-alanine is normally the limiting ingredient, taking beta-alanine as a supplement reliably raises the carnosine content of muscle ^[1]. This is the basis for the popularity of beta-alanine among athletes, since higher muscle carnosine has been linked to improved performance in high-intensity, fatiguing exercise ^[1]. Carnosine itself is also sold directly as a supplement, although much of an oral dose is broken down in the blood by the enzyme carnosinase before it reaches the tissues, which complicates the interpretation of oral carnosine studies ^[4].

Beyond exercise, carnosine has been investigated as a geroprotective and neuroprotective agent ^[2][3]. Laboratory and early clinical work has examined its antioxidant and antiglycation actions in the context of aging, neurodegenerative disease, and stroke, and it has been studied for possible benefit in Parkinson's disease and in diabetic complications ^[2][3][4]. A derivative, N-acetylcarnosine, has been used in eye drops aimed at cataract, and a similar dipeptide called anserine occurs in the muscle of birds and fish ^[4]. Much of this therapeutic evidence remains preliminary.

Carnosine is regulated as a dietary supplement rather than a drug. A rare inherited disorder called carnosinemia, caused by deficiency of the enzyme that breaks it down, illustrates the consequences of disrupted carnosine metabolism, but for most people carnosine is simply a normal component of muscle and a well-tolerated supplement ^[4].

Carnosine is generally very safe and is a normal dietary component, especially from meat. Side effects are uncommon at typical doses. Because it can lower blood pressure slightly and influence blood sugar handling, people on related medications should just be aware.