Assimilation of lactitol, an 'unabsorbed' disaccharide in the normal human colon

The fate of orally ingested lactitol, a non-absorbed sugar, was measured in six healthy human subjects by following the three routes of disposal of universally 14C-labelled sugar. Lactitol was given as a 20 g daily dose to six healthy volunteers for 14 days and on the seventh day, 10 muCi of L-[U-14C]-lactitol was given with the unlabelled sugar and excretion of the 14C in breath, urine and faeces was followed. The peak of 14CO2 excretion occurred at six hours and total 14CO2 accounted for 62.9 (5.0)% of isotope given, whilst 6.5 (3.6)% and 2.0 (0.3)% of the label were recovered from faeces and urine respectively. These data suggest that lactitol is extensively metabolised in the human colon and that a significant proportion of the bacterial metabolites are available for colonic absorption. Calculation revealed that 54.5% of the theoretical energy content of this compound was utilised by the subjects. It is suggested that this sugar, and other soluble 'non-absorbed' sugars (lactulose, sorbitol, mannitol), may undergo a similar pattern of colonic metabolism and can be considered as reduced calorie compounds.