:Histidine:
Function: Antiarthritic.
Histidine is an essential amino acid for infants but not adults. Infants
four to six months old require 33 mg/kg of histidine. It is not clear
how adults make small amounts of histidine, and dietary sources probably
account for most of the histidine in the body. Inborn errors of histidine
metabolism exist and are marked by increased histidine levels in the
blood. Elevated blood histidine is accompanied by a wide range of
symptoms, from mental and physical retardation to poor intellectual
functioning, emotional instability, tremor, ataxia and psychosis.
Histidine in medical therapies has its most promising trials in rheumatoid
arthritis where up to 4.5 g daily have been used effectively in severely
affected patients. Arthritis patients have been found to have low
serum histidine levels, apparently because of too-rapid removal of
histidine from their blood. Histidine and other imidazole compounds
have antiinflammatory properties. Histidine may accomplish this function
through a complex interaction with threonine or cysteine and possibly
copper. However, copper is usually elevated in rheumatoid arthritis
patients and worsens the disease.
Other patients besides arthritis patients that have been found to
be low in serum histidine are those with chronic renal failure. Histidine
has been claimed to have been useful in hypertension because of its
vasodilatory effects. Claims of its use to improve libido and counteract
allergy are without proof at present.
Histidine may have many other possible functions because it is the
precursor of the ubiquitous neurohormone-neurotransmitter histamine.
Histidine increases histamine in the blood and probably in the brain.
Low blood histamine with low serum histidine occurs in rheumatoid
arthritis patients. Low blood histamine also occurs in some manic,
schizophrenic, high copper and hyperactive groups of psychiatric patients.
Histidine is a useful therapy in all low histamine patients.
Effective therapeutic doses of histidine may range from 1 to 5 g per
day. Therapy can be guided by measuring plasma histidine levels.
