Measurement of the mean transit time of dietary residue through the human gut.

A new method is described for measuring the mean transit time (MTT) of digesta through the human gut in which a constant amount of marker (radio-opaque pellets) is fed to subjects with each meal over a period of weeks, and its excretion measured in the stools. The MTT measured by this method (MTT-C) has been compared with MTT measured by giving single doses of similar markers to the same subjects (MTT-S) and with the 80% transit time (80% TT). Mean values on three dietary regimes for the MTT-C (54.2 h +/- 2.5) and MTT-S (54.2 +/- 2.6) were lower than that for 80% TT (63.1 +/- 3.0). The average MTT-C in a group of six healthy young men on an ad libitum diet was 2-3 days (range 0-7-4-0). When additional dietary fibre was added to a standard diet the average MTT-C fell (in all of five subjects) from 2-4 to 1-6 days. A continuous record of MTT-C is obtained by this new method which shows wide variations from week to week even on controlled dietary intakes. Using the single dose technique, evidence is produced which suggests that the MTT-S is a more accurate and reproducible method than the 80% TT.