Is the rat a suitable model for humans on studies of cereal digestion?

OBJECTIVES

To compare the extent of starch digestion from barley flake and flour in humans and rat. Is the rat a useful model?

DESIGN

Four healthy male ileostomy volunteers consumed, in random order, flapjacks containing flaked barley on one occasion and barley flour on another. Ileostomy fluid was collected for analysis of starch and nonstrach polysaccharide (NSP) hourly for 12 h. The ratio of starch to NSP in ileostomy fluid was compared with that in the terminal ileum of eight randomly selected male rats consuming the flaked barley flapjack and another eight rats consuming the barley flour flapjack.

RESULTS

After consuming flaked barley the terminal ileal starch-NSP ratio was 20 times lower in rats than in ileostomists and was 0.04 (s.e.m. 0.006) g/g compared with 0.89 (s.e.m. 0.05) g/g respectively. By contrast the starch-NSP ratio was very low after consuming the barley flour in both species; however the ratio was still lower in rats than in ileostomists and was 0.02 (s.e.m. 0.01) g/g compared with 0.05 (s.e.m. 0.01) g/g respectively. Using the NSP as an indigestible marker, starch from barley flake that resisted small intestinal digestion was calculated to be 0.7 (s.e.m. 0.02)% in rats compared with a higher value of 17 (s.e.m. 1)% in ileostomists.

CONCLUSION

The cell walls of barley flake limit the extent of starch digestion in humans but in rats this appears not to be a limiting factor. In the present instance it was not possible to extrapolate results from rats to humans.