DIGESTION OF CARBOHYDRATE FROM WHITE BEANS (PHASEOLUS-VULGARIS L.) INHEALTHY HUMANS

Resistant starch (RS) is thought to be present in targe amounts in leg ume seeds; however, it has never been quantified in healthy humans. RS from cooked (atmospheric pressure) white beans was quantified in huma ns and pigs, and characterized to explain its low digestibility. Six h uman volunteers were intubated to collect ileal digesta after an exper imental meal composed of orange juice, butter and 167 g beans (dry mat ter basis). The reliability of the intubation method was examined in a pig study in which it was compared with another collection method, il eal cannulation. Chemical analyses, microscopy and size exclusion chro matography were performed on human and pig digesta. The pig study show ed that the intubation method may underestimate the quantity of RS. Ho wever, no chemical/physical difference was observed between the RS col lected by the two techniques. In the human study, 16.5 +/- 1.3% (11.3 g) of the ingested starch was recovered as RS. The microscopy of the d igesta showed that part of the RS was enclosed in the cell walls. Alth ough the RS was composed mainly of alpha-glucan molecules with a degre e of polymerization (DP) 40 to 60, oligosaccharides and large molecule s of DP > 400 were also present. Retrogradation was not found to be th e main factor responsible for starch malabsorption. We conclude that w hite beans may contain a large amount of RS formed mainly by partially degraded molecules protected by the cell walls during their transit t hrough the gut.