Effects of high-resistant-starch banana flour (RS(2)) on in vitro fermentation and the small-bowel excretion of energy, nutrients, and sterols: an ileostomy study.

BACKGROUND Resistant starch (RS) has attracted interest because of its effects in the colon and implications for health. Knowledge of how RS influences small-intestinal absorption of nutrients, sterol metabolism, and colonic fermentation is sparse. OBJECTIVES The objectives of this study were to measure the effect of RS(2), a type of RS in banana flour, on the ileal excretion of energy, nutrients, and sterols, and to compare in vivo measurement of RS in the ileostomy model with previously published intubation data. In addition, we sought to estimate a fermentation pattern by using ileal effluents for in vitro fermentation. DESIGN The present study was divided into 2 parts. Study A involved 10 ileostomy subjects who were given a controlled diet with the addition of 30 g raw green banana flour (RBF)/d, which contains RS(2), or cooked green banana flour (CBF)/d in random order. Study B involved 7 ileostomy subjects who were given a plant-polysaccharide-free diet with the addition of 30 g RBF/d. RESULTS In study A, the dry weight of the ileostomy effluents and the ileal excretion of energy, iron, and chenodeoxycholic acid, but not total sterols, were higher after the addition of RBF than of CBF to the diet. In vitro fermentation of the ileal effluents obtained after the addition of RBF to the diet showed higher concentrations of acetate and butyrate. In study B, the ileal excretion of starch was lower than the amount calculated from earlier studies by use of the intubation technique. CONCLUSIONS The addition of RBF containing RS(2) to the diet of ileostomy subjects did not interfere with small-bowel absorption of nutrients or total sterols, except for a small increase in iron excretion. The ileostomy model seems to give reliable results for in vivo measurement of RS.