Histidine

Mechanism

Histidine is an essential amino acid and the direct precursor of the dipeptide carnosine (beta-alanyl-L-histidine), which occurs in high concentration above all in the fast-contracting type II muscle fibres of the horse, where it acts as an intracellular pH buffer as well as an antioxidant and metal chelator. Equine muscle analyses show very high carnosine contents, particularly in glycolytic fibres. Carnosine synthesis, however, is limited predominantly by the availability of beta-alanine and not of histidine, so that pure histidine supply raises muscle carnosine content only to a limited degree. Histidine/carnosine has been associated with the field of muscular acid buffering during intense, anaerobic exertion. Much of the mechanistic rationale comes from human sports physiology; controlled equine performance data are limited. A specific histidine requirement is not separately quantified in NRC 2007 and GfE 2014.

Cautions

• · Muscle carnosine is limited primarily by beta-alanine - histidine alone barely raises carnosine content.
• · Usually already covered via normal ration protein; isolated supplementation rarely necessary.
• · Equine performance data limited; transfer predominantly from human sports physiology.

Sources