Effect of single ingestion of Guava Leaf Tea on postprandial blood glucose elevation in human subjects. (a) Time course of changes in blood glucose level. (b) Area under the curve in changes in blood glucose level. Nineteen subjects aged over 40 years, with or without pre-diabetes, with an FBG level of 103.0 ± 14.3 mg/dL and a body mass index (BMI) of >22.0 were recruited. After overnight fasting for 11 hours, the subjects ingested 200 g of cooked rice as a loading carbohydrate together with a bottle (190 mL) of hot water at week 1 and then with the same volume of Guava Leaf Tea containing about 400 mg of GvEx at week 2. Blood glucose level was measured at 30-min intervals for up to 150 min after ingestion. *: p < 0.05, **: p < 0.01 (paired t-test) .