Dietary fiber effects on passage rate and breath hydrogen

Fermentation of fiber and passage to the large intestine were monitored by measuring hydrogen gas (H2) concentration in expired breath. Five subjects consumed meals containing no added fiber or 40 g of wheat bran (WB), corn bran (CB), oat bran (OB), or citrus flour (CF) replacing white flour. Breath samples were obtained at 30 min intervals for 9 h after the test meals. Mean H2 concentration (ppm), averaged over the 9 h test period, ranged from 7.5 (CB) to 12.0 (OB) and tended to increase with addition of OB, CF, or WB but decrease with addition of CB. Hours from the meal to the highest H2 peaks were 4.7 (WB), 5.6 (CB), 6.2 (OB), 6.4 (CF), and 8.2 (basal). The gel-like fibers (OB and CF) resulted in greater H2 concentration and less acceleration of passage rate than the particulate fibers (WB and CB).