Dietary fibre: The use of in‐vitro and rat models to predict action on stool output in man

An in‐vitro model (fermentation and water holding capacity measurement) and a rat model were compared for their ability to predict the action of dietary fibre on stool output in man. A range of different purified or semipurified fibres were studied: wheat bran, pectin, carboxymethylcellulose, xanthan, guar, karaya, tragacanth and gellan. Using equations derived from previous studies, prediction indices from in‐vitro studies were compared with the effects of these fibres on stool output in rat and man. The rat model was better as a predictor for stool output (r = 0.94, P < 0.005) in man but the log in‐vitro predictive index was significantly correlated with stool output in both rat (r = 0.87, P < 0.02) and man (r = 0.84, P < 0.04). Since in‐vitro methods are less expensive and time consuming than animal studies, the log in‐vitro predictive index may provide a useful pre‐screening device for new dietary fibre sources or detecting changes in the action of dietary fibres during the manufacturing process.