Does guar gum improve post-prandial hyperglycaemia in humans by reducing small intestinal contact area?

The possibility that viscous polysaccharides, such as guar gum, could lower post-prandial blood glucose levels in part by restricting carbohydrate solutions to a smaller area of small intestine was investigated in twenty healthy human volunteers. Addition of guar gum (22.5 g/l) delayed the mouth-to-caecum transit time of a hypotonic lactulose drink, but did not affect gastric emptying. When a 250 ml solution containing 50 g glucose was confined to a 550 mm length of intestine by an occluding balloon attached to an intestinal tube, maximum blood glucose response was significantly reduced (P less than 0.05) though only by 0.9 mmol/l. Addition of guar gum (36 g/l) had no effect on the distribution of a radio-labelled glucose drink (250 ml; 200 g glucose/l) in the small intestine, monitored using a gamma camera, although it significantly delayed gastric emptying (t 1/2 (min): guar gum v. control 115 (SE 15) v. 73 (SE 8)). Reduced contact area is unlikely to be one of the mechanisms by which guar gum improves glucose tolerance.