Excretion of Histidine and Histidine Derivatives by Human Subjects Ingesting Protein from Different Sources

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Abstract
The 1-methylhistidine, histidine, 3-methylhistidine, anserine (β-alanyl-1-methylhistidine), and carnosine (β-alanylhistidine) content of urine from 5 subjects was determined by ion-exchange chromatography. Controlled diets containing 2 levels of protein were fed; one series contained protein from animal flesh; the other contained no flesh protein. More of the histidine derivatives were excreted by subjects eating the flesh protein diets than by those eating the non-flesh diets. The former subjects also responded to increased protein intake with increased excretion of the derivatives; the latter did not. 1-Methylhistidine excretion tended to parallel intake. Both of the dipeptides, anserine and carnosine, were present in the urine of all the subjects whether or not they were present in the diets; thus their source could be either exogenous or endogenous, or both. 3-Methylhistidine was not present in any of the foods analyzed (beef, chicken, milk, bread) but was present in the urine of all of the subjects. Its source is not known.