The observation that berries have beneficial glycaemic effects has lead to scientific investigations into the cause of this phenomenon. A number of components within berries have been identified as possessing possible glycaemic effects including the fibre, acids, the natural sugars and the anthocyanins. Evidence suggests that perhaps all of these components, and perhaps a component yet to be identified, work synergistically to produce beneficial glycaemic effects in humans. Anthocyanins are of particular interest because they have also been identified as biologically active antioxidants in humans. They therefore are suspected of providing significant health benefits for this reason. However, their ability to preserve the normal function of the insulin system makes them particularly interesting because aberrations to this system are increasingly being seen as a cause of Western lifestyle diseases including cardiovascular disease, obesity, metabolic syndrome and type 2 diabetes.
While berries have been extensively investigated for their ability to produce beneficial glycaemic effects, purified anthocyanin supplements have not been used so widely in studies. However, to date a number of studies investigating the effects of anthocyanin supplements of human subjects have shown beneficial effects. For example, in one study1, researchers administered 160 mg of anthocyanins twice daily to a group of subjects with type 2 diabetes over 24 weeks. Compared to a placebo treatment, the anthocyanin supplements caused a significant reduction in plasma low density lipoprotein (LDL), triglycerides (very low density lipoprotein; VLDL) and apolipoprotein B48 (a marker for intestinal chylomicrons). At the same time the anthocyanin group experienced higher plasma high density lipoprotein (HDL) and higher antioxidant status. These changes may be explained by the significant improvements in fasting plasma glucose and improved insulin resistance seen in the anthocyanin group.