Pullulan is an extracellular polysaccharide excreted by the fungus Aureobasidium pullulans. To evaluate the glycemic and breath hydrogen responses and gastrointestinal tolerance to pullulan, nondiabetic healthy adult subjects (n = 28) were studied in a randomized, double-masked, crossover design. After an overnight fast, subjects consumed beverages containing 50 g of carbohydrate from either maltodextrin (control) or pullulan. Capillary blood glucose response was determined for 180 min postprandially. Breath hydrogen response was determined for 8 h postprandially. Compared with control, incremental peak blood glucose concentration was reduced (P < 0.01) when subjects consumed pullulan (4.24 +/- 0.35 vs. 1.97 +/- 0.10 mmol/L). In addition, pullulan reduced (P < 0.01) the positive incremental area under the glucose curve by 50%. When subjects consumed pullulan, the incremental blood glucose excursions were reduced (P < 0.01) at 15, 30, 45, 60 and 90 min, but were maintained above basal glucose concentrations at 150 and 180 min. At 180 min, the blood glucose concentration was higher (P < 0.05) when subjects consumed pullulan compared with control, supporting the hypothesis that pullulan is digested slowly. Breath hydrogen concentrations were increased (P < 0.01) at 3, 4, 5, 6, 7 and 8 h postprandially when subjects consumed pullulan. In the first 24-h postprandial period, the frequency and intensity of flatulence was higher (P < 0.05) after subjects consumed pullulan compared with control. In conclusion, pullulan attenuated the postprandial glycemic excursion compared with an equivalent maltodextrin challenge. Pullulan also increased breath hydrogen excretion and the incidence of gastrointestinal intolerance symptoms, indicating that a portion of pullulan was malabsorbed.