US researchers determined the effect of different doses of Salacia oblonga extract, a herbal alpha-glucosidase inhibitor, on post-prandial glycaemia, insulinaemic and breath hydrogen responses in 39 healthy adults in a double-blind, randomised crossover trial. After fasting for 12 h, subjects 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 1000 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 h post-prandially. Breath hydrogen excretion was measured at baseline and hourly for 8 h post-prandially. Compared with the control, the 1000-mg S. oblonga extract dose reduced the plasma glucose and serum insulin incremental areas under the curve (0 to 120 min post-prandial) by 23 and 29%, respectively. The other doses of S. oblonga extract did not impact glycaemia or insulinaemia. Breath hydrogen excretion increased linearly as the dose of S. oblonga extract was advanced.