Alnajjar, M., Barik, S.K., Bestwick, C., Campbell, F., Cruickshank, M., Farquharson, FM., Holtrop, G., Horgan, G.W., Louis, P., Moar, K.M., Russell, W., Scobbie, L. and Hoggard, N.
||Dietary strategies for alleviating health complications associated with type 2 diabetes (T2D) are being pursued as alternatives to pharmaceutical interventions. This study investigated the effect of a three week supplementation of concentrated bilberry extract on glucose metabolism.
Overweight volunteers (n=16; BMI 31, SD 4), nine of whom have T2D controlled by diet and lifestyle alone, were given three oral capsules of either 0.47g standardized bilberry extract (36% (w/w) anthocyanins) or placebo per day for three weeks in a double blinded cross over intervention. Volunteers were given an OGTT at the beginning and end of each intervention period. The ingestion of the bilberry extract resulted in a significant decrease in the OGTT AUCi for glucose (20%; p=0.008) but not insulin (p=0.945) compared with the placebo. There was no change in anti-inflammatory markers (hsCRP, MCP-1, leptin), markers of vascular health (Apo A1, sVCAM-1, sICAM-1) in the plasma, anti-oxidant (TEAC, FRAP) responses or change the faecal bacterial microbiota measured between the volunteers receiving the bilberry extract and the placebo suggesting these are later events. In vitro studies showed that the bilberry extract decreased á-amylase activity (p<0.0001), á-glucosidase activity (p<0.0001) and glucose uptake (p<0.0001).
In conclusion this demonstrates that the ingestion of a concentrated bilberry extract over a three week intervention period reduces postprandial glycaemia without changes in insulin in volunteers with T2D. We show that the most likely mechanism for the early decreased glycaemic response which leads to the later changes in insulin involves reduced rates of carbohydrate digestion and/or absorption.