Effects of Oral Histamine, Histidine and Diet on Urinary Excretion of Histamine, Methylhistamine and 1-Methyl-4-imidazoleacetic Acid in Man

The urinary excretion of l-methyl-4-imidazoleacetic acid (1,4-MeImAA) was measured in eight healthy subjects. In some experiments the excretion of histamine and methylhistamine was determined simultaneously. Large amounts of histamine by mouth increased the urinary excretion of 1,4-MeImAA, whereas there were no certain effects of histidine or 3-methylhistidine. There were indications that dietary factors other than the histamine content of the food may be of importance for the large variations in the urinary excretion of 1,4-MeImAA sometimes seen in subjects given a mixed diet. A high protein intake, sometimes, but not consistently, increased the urinary excretion of 1,4-MeImAA. Other possibly important factors discussed are the absorption of histamine from the intestine and the role played by the intestinal bacterial flora. It is suggested that investigations of histamine melabolism in man may have to be performed under standardized dietary conditions.