Effect of guar on second-meal glucose tolerance in normal man

Whole body glucose turnover and absorption of a 50 g glucose drink was studied in six healthy volunteers on two occasions, 4 h after a 'breakfast' of 50 g of glucose, mixed on one occasion with 20 g of guar gum. Plasma glucose concentrations were significantly reduced with guar gum compared with those obtained without guar gum (P less than 0.0001). Whole body glucose turnover studied by an intravenous primed dose constant infusion technique using D-[3-3H]glucose showed no significant difference between the two groups: 353 +/- 15 mmol with guar and 350 +/- 9 mmol without guar. Total oral glucose absorption, followed with a D-[1-14C]glucose tracer, was significantly decreased by guar treatment, being 219 +/- 3 mmol with guar and 239 +/- 5 mmol without guar (P less than 0.05). Serum insulin levels were lowered by guar treatment (P less than 0.05) while those of C-peptide, gastric inhibitory polypeptide, glucagon, cortisol and pancreatic polypeptide did not differ significantly. Blood lactate concentrations were raised in the guar treated group (P less than 0.05) whereas pyruvate, alanine, glycerol and 3-hydroxybutyrate concentrations did not differ significantly. These results support the suggestion that guar improves second-meal tolerance to glucose by decreasing absorption.