Urinary excretion of histamine and some of its metabolites in man: influence of the diet.

Urinary excretions of histamine, N tau-methylhistamine and N tau-methylimidazoleacetic acid have been determined in 10 normal subjects on 3 different diets, containing a very low protein, a low protein and a high protein amount. Foodstuffs which could contain histamine were excluded. The mean excretion of N tau-methylhistamine on the second day of each diet amounted to 0.861 mumol/24 h, 1.051 mumol/24 h and 1.378 mumol/24 h, respectively. The excretions of histamine and N tau-methylimidazoleacetic acid were not affected. In 6 normal persons on a protein low diet, the excretions of histamine, N tau-methylhistamine and N tau-methylimidazoleacetic acid have been determined for 10 days. On the fifth day, to 3 persons 200 mumol of histamine was given orally, the other 3 persons received a high protein diet. The persons receiving histamine showed a strongly enhanced excretion of N tau-methylimidazoleacetic acid, corresponding to 36.1% of the administered histamine, whereas the urinary excretions of histamine and N tau-methylhistamine were only slightly elevated. On the high protein diet, only the excretion of N tau-methylhistamine was slightly elevated. The urinary excretions of histamine in the female subjects sometimes showed unexpectedly high values. Most probably, this phenomenon is attributable to bacterial histamine production in the urogenital tract.