Subjects will arrive at the center in a fasting state for at least 10 hours, well hydrated and rested. Each OGTT Day will require blood draws throughout the visit. After evaluation of subject's health status (via anthropometric, vital sign and blood glucose measurements and in-person interview), a registered nurse will place a catheter in subject's arm for the purpose of multiple blood sample collections and take the initial blood draw (baseline: -1h) in the fasting state. 3 test capsules with 0 mg GSE, 300 mg GSE, 600 mg GSE or 900 mg GSE (in forms of: 3 placebo, 2 placebo & 1 GSE, 1 placebo & 2 GSE or 3 GSE. Each GSE capsule containing 300 mg GSE) will be served. Thereafter, timers will be started and a glucose test drink (75g glucose mixed with 250ml water) will be given right after the 0h blood sampling (1 h after the consumption of capsules). Subject will be instructed to finish the drink in 5 minutes (min). From this point forward, blood sample will be collected at 30 min, 1h, 2hand 3h for assessment of changes in metabolic markers. The sequence of receiving the capsules treatment at each visit will be randomly assigned based on computer generated sequences.