Evidence for the mixing of residue in the human gut.

Mixing the residue in the gut has been studied in 24 normal subjects using five different types of radio-opaque pellets. By giving single doses of different pellets to the subjects on three successive days and measuring their appearances in the stool by radiographs evidence of mixing was found in 83% of studies. Mean transit time (MTT) of markers through the gut was measured from the single dose studies (MTT-S) and also by giving the pellets to subjects continuously with each meal (MTT-C). By comparing MTT-C with MTT-S evidence was found for a mixing pool with exponential decay. The turnover time of this pool was estimated as about 30% of the total MTT.