Anthocyanin-enriched bilberry extract attenuates glycaemic response in overweight volunteers without changes in insulin

This study investigated the effect of a three week supplementation of bilberry extract on glucose metabolism. Overweight volunteers (n = 16; BMI 31) were given three capsules of either 0.47 g bilberry extract (36% (w/w) anthocyanins) or placebo per day for three weeks in a double blinded cross over intervention. The ingestion of the bilberry extract decreased the OGTT AUCi for glucose (20%; p = 0.008) but not for insulin compared with the placebo. There was no change in anti-inflammatory markers (hsCRP, MCP-1, leptin), vascular health markers (Apo A1, sVCAM-1, sICAM-1), reducing potential/ radical scavenging capacity or faecal bacterial microbiota. In vitro studies showed that the bilberry extract decreased α-amylase activity (p < 0.0001), α-glucosidase activity (p < 0.0001) and glucose uptake (p < 0.0001). This study demonstrates that the ingestion of a bilberry extract over a three week intervention period reduces postprandial glycaemia without changes in insulin. This is probably due to reduced rates of carbohydrate digestion and/or absorption.