J Nutr 1999 Jul;129(7 Suppl):1436S-7S

Caloric value of inulin and oligofructose.

Roberfroid MB

Department of Pharmaceutical Sciences, Universite Catholique de Louvain, B-1200
Brussels, Belgium.

Dietary carbohydrates, which are absorbed as hexose, (glucose, fructose) have a
caloric value of 3.9 kcal/g (16.3 kJ/g), and their cellular metabolism produces
approximately 38 mol ATP/mol. However, chicory inulin and oligofructose resist
digestion and they are not absorbed in the upper part of the gastrointestinal
tract. After oral ingestion, they reach the colon intact where they become
hydrolyzed and extensively fermented by saccharolytic bacteria, which produce
short-chain carboxylic and lactic acids as electron sinks. Depending on both the
degree of their colonic fermentation and the assumptions of the model used, the
caloric value of such nondigested but fermented carbohydrates varies between 0
and 2.5 kcal/g. Through the catabolism of the absorbed short-chain carboxylic
and lactic acids, they may produce up to 17 mol ATP/mol of fermented sugar
moiety. Because the daily intake of these dietary carbohydrates is likely to
remain relatively small (<10% and probably often not >5% of total daily calorie
intake), it is of low relevance nutritionally to give them a precise caloric
value. On the basis of biochemical balance charts for carbon atoms, metabolic
pathways and energy yields to the host, the caloric value of a fructosyl residue
in chicory inulin and oligofructose has been calculated to be approximately
25-35% that of a fully digested and absorbed fructose molecule. For the purpose
of food labeling, it is recommended that chicory inulin and oligofructose, like
all the other carbohydrates that are more or less completely fermented in the
human colon, should be given a caloric value of 1.5 kcal/g (6.3 kJ/g).

Publication Types:
Review
Review, tutorial

PMID: 10395615, UI: 99335754