Effects of a medical food containing an herbal alpha-glucosidase inhibitor on postprandial glycemia and insulinemia in healthy adults

Objective To determine the effect of different doses of Salacia oblonga extract, an herbal alpha-glucosidase inhibitor, on postprandial glycemic, insulinemic, and breath hydrogen responses in healthy adults. Design Double-masked, randomized crossover design. Intervention Subjects, after fasting for 12 hours, consumed four test meals consisting of 480 mL of study beverage (14 g fat, 82 g carbohydrate, and 20 g protein) with 0, 500, 700, or 1,000 mg of S oblonga extract on four separate occasions. Capillary finger-prick plasma glucose and venous serum insulin concentrations were measured at baseline and for 2 hours postprandially. Breath hydrogen excretion was measured at baseline and hourly for 8 hours postprandially. Subjects/Setting Thirty-nine healthy, nondiabetic adults (body mass index=23.7+/-0.4, age=25.7+/-0.9 years. Statistical Analyses Performed Repeated-measures analysis of variance was applied to the raw data or data that had been transformed (log, rank) when necessary due to nonnormality. The Tukey-Kramer post hoc test was used for pairwise comparisons. Results Compared with the control, the 1,000-mg S oblonga extract dose reduced the plasma glucose and serum insulin incremental areas under the curve (0 to 120 minutes postprandial) by 23% (P=.32) and 29% (P=.01), respectively. The other doses of S oblonga extract did not impact glycemia or insulinemia. Breath hydrogen excretion increased linearly as the dose of S oblonga extract was advanced. Conclusions The presence of S oblonga extract tended to lower postprandial glycemia and significantly reduced the postprandial insulin response. The increase in breath hydrogen excretion suggests a mechanism similar to prescription alpha-glucosidase inhibitors. Future studies of S oblonga extract in patients with diabetes are needed.