The potential anti-diabetes effects of the berries are linked to the anthocyanin content, which may affect the action of various proteins involved in the glucose transport and fat metabolism, according to findings published in The Journal of Nutrition.
With the number of people are affected by diabetes in the EU 25 projected to increase to 26 million by 2030, up from about 19 million currently – or 4 per cent of the total population –approaches to reduce the risk of diabetes are becoming increasing attractive.
If further studies, particularly in humans, support the potential benefits of bilberries it could see an interesting addition to the market.
The statistics are even more startling in the US, where almost 24 million people live with diabetes, equal to 8 per cent of the population. The total costs are thought to be as much as $174 billion, with $116 billion being direct costs from medication, according to 2005-2007 American Diabetes Association figures.
Led by Takanori Tsuda from Chubu University, the Japanese researchers looked at how bilberries may influence glucose and lipid metabolism in mice with a genetic predisposition for diabetes. The animals were fed a diet with or without supplemental bilberry extract (27 g/kg diet, Tama-Biochemicals, Japan) for five weeks.
At the end of the study, the results showed that consumption of the bilberry extract was associated with lower blood glucose levels and increased insulin sensitivity. This was linked to an activation of a protein which stimulates lipid breakdown in liver and muscle and modulates insulin secretion by the pancreas called AMP-activated protein kinase (AMPK).
Increases in levels of a glucose transporter were also noted by the researchers, and this was accompanied by a simultaneous activation of an enzyme linked to fatty acid synthesis (acetyl-CoA carboxylase), and inactivation of enzymes that play a role in fat metabolism.
“Our findings provide a biochemical basis for the use of bilberry fruits and also have important implications for the prevention and treatment of type 2 diabetes,” wrote the researchers.
Bilberries are closely related to the North American blueberry but contain a very distinct anthocyanin profile. Bilberry extracts are relatively expensive. Concerns are rife within the industry of lower-price extracts reported to be mixed with mulberry or black bean skins or azo-dyes.
Concerns were raised in 2006 when Australian scientists discovered that azo dyes were used to mimic the colour of bilberries in a commercial product (J. Agric. Food Chem, Vol. 54, Issue 19, pp. 7378 -7382). This has since expanded to reports of mulberry or black bean skins being used to increase the anthocyanin content of the extracts.
The anthocyanins content is used as the standard for bilberry, and UV spectrometry is needed to verify the 25 per cent anthocyanins. However, according to unconfirmed reports, this has led to extracts masquerading as bilberry but actually containing mulberry (22-24 per cent), or black bean skin (20 per cent).
Source: Journal of Nutrition
Volume 140, Pages 527-533
“Dietary anthocyanin-rich bilberry extract ameliorates hyperglycemia and insulin sensitivity via activation of AMP-activated protein kinase in diabetic mice”
Authors;: Takikawa M, Inoue S, Horio F, Tsuda T...