Histidine is classified as an essential amino acid for infants and a conditionally essential amino acid for adults. It is the precursor of histamine – the first line of immunological defense. It is vital to the maintenance of a healthy myelin sheath (the tissue that coats nerves and helps in the transmission of nerve impulses). High levels of histidine have been linked to anxiety and schizophrenia, while low levels contribute to the development of rheumatoid arthritis and deafness (the type that results from nerve damage). Histidine also acts as a natural detoxifier, protecting against radiation damage, and removing heavy metals from the body. Good sources are meat, grains and dairy products. Supplementation doses range from 500 milligrams to 4.5 grams daily.

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Histamine has been implicated as one of the mediators involved in regulation of proliferation in both normal and neoplastic tissues. Histidine decarboxylase, the only enzyme that catalyzes the formation of histamine from L-histidine, is an essential regulator of histamine levels. These findings suggest that expression of histidine decarboxylase is elevated in human melanoma.

o       J Invest Dermatol. 2000 Sep; 115(3): 345-52.

·        A long-term histidine deficient diet (1-8 wk) which could potentially be brought about through chemotherapy, leads to a significant decrease in plasma histidine concentrations.

o       Histidine III, p. 2. Wiss. Verlagsgesellschaft, Stuttgart, Germany.