Effect of Viscous Fiber (Guar) on Postprandial Motor Activity in Human Small Bowel

Abstract

Both caloric value and chemical composition ofa meal have been shown to regulate postprandial smallbowel motility in dog. In the same species, duration ofand contractile activity within the postprandial period also depends on mean viscosity. It isunknown, however, whether meal viscosity and fibercontent also regulate small bowel motor activity in man.In human volunteers, we therefore studied the effect of guar gum on small bowel motor response toliquid and solid meals. Twenty-six prolonged ambulatorysmall bowel manometry studies were performed in 12volunteers. A total of 620 hr of recording were analyzed visually for phase III of the MMC and avalidated computer program calculated the incidence andamplitude of contractions after ingestion of water (300ml), a pure glucose drink (300 ml/330 kcal) or a solid meal (530 kcal) with and without 5 g of guargum. Addition of 5 g of guar gum did not significantlydelay reappearance of phase III after ingestion of water(59 ± 11 vs 106 ± 21 min; P = 0.09).However, guar gum significantly prolonged duration ofpostprandial motility pattern both after the glucosedrink (123 ± 19 vs 199 ± 24 min; P <0.05) and after the solid meal (310 ± 92 vs 419± 22 min; P = 0.005). Contractile activity during these periods was not affected by guargum. This was true for mean incidence of contractionsafter water (1.9 ± 0.3 vs 1.8 ± 0.5min^-1), after the glucose drink (1.6 ±0.4 vs 1.7 ± 0.3 min^-1) and after the solid meal (2.4 ± 0.4 vs 2.6 ±0.4 min^-1). Likewise, mean amplitude ofcontractions was not affected by guar gum after water(22.8 ± 1.4 vs 20.9 ± 1.9 mm Hg), afterthe glucose drink (20.5 ± 1.4 vs 21.3 ±1.2), and after the solid meal (20.3 ± 1.5 vs 21.5± 1.6 mm Hg). Thus a guar gum-induced increase inchyme viscosity markedly prolonged duration ofpostprandial motor activity in the human small bowel.Contractile activity within the postprandial period, however, wasnot affected. We suggest that the postprandial motilitypattern persisted longer after the more viscous meals,because gastric emptying and intestinal transit were delayed by guar gum. We conclude that itis essential to define meal viscosity and fiber contentwhen studying postprandial small bowelmotility.