The effect of saccharin on the microbial metabolism of tryptophan in man.

The microbial catabolism of tryptophan to indole has been studied in 15 human subjects by analysis of the daily urinary excretion of indican (potassium indoxylsulphate) before, during and after chronic saccharin ingestion. The daily excretion of indican during a 3-wk control period showed marked inter- and intra-subject variability. Analysis of the urinary excretion of saccharin during chronic administration demonstrated good compliance for both saccharin ingestion and urine collection. The urinary excretion of indican was not increased significantly by the ingestion of saccharin (1 g/day as divided doses with meals) for one month. These findings are consistent with epidemiology studies which show the absence of a consistent excess risk of cancer of the urinary bladder in humans ingesting saccharin as a food additive.