Effects of selected antioxidant food extracts on postprandial glucose responses in healthy individuals

Background: Obesity and diabetes are highly prevalent in Western countries. Both of these conditions can be associated with impaired glucose control and hyperglycemia. Studies have identified that antioxidants have the ability to regulate blood glucose levels. However, the effects of specific high-antioxidant food extracts on blood glucose levels have not been well characterized. Thus, this study aimed to measure the effects of selected antioxidant food extracts on postprandial glucose responses in healthy individuals. Methods: Ten healthy individuals were recruited into a randomized, single-blinded study. Participants consumed five different high-antioxidant food extracts (one per session, each >48 hours apart) that were matched for total antioxidant content 10 mins prior to ingestion of 50 g of available carbohydrate from either a glucose load or white bread (with ham) after an overnight fast. Blood glucose levels were measured using capillary sampling every 15 mins for two hours and the incremental area under the glucose curve (IAUC) was also measured. The IAUC values for the test foods were compared to the glucose-only and bread-only controls. Results: Amla berry-, grape seed-rooibos tea-and green tea-extracts as well as propolis tincture were all strong glycemic modulators, significantly decreasing the IAUC by 25-40% compared to the glucose-only or white bread controls (all p < 0.05). Conclusion: Antioxidants are able to modulate postprandial glucose responses in healthy subjects. These results suggest that further research is warranted to determine whether these antioxidant-rich foods are beneficial to people with prediabetes or type 2 diabetes mellitus.