A Single Supplement of a Standardised Bilberry Extract Modifies Glycaemic Response
Condition: Type 2 Diabetes
MeSH terms: Diabetes Mellitus, Type 2
Study type: Interventional

Summary: 
      Dietary strategies for alleviating health complications associated with type 2 diabetes (T2D)
      are being pursued as alternatives to pharmaceutical interventions. Berries such as bilberries
      that are rich in polyphenols may influence carbohydrate digestion and absorption and thus
      postprandial glycaemia. In addition berries have been reported to alter incretins as well as
      to have anti-oxidant and anti-inflammatory properties that may also affect postprandial
      glycaemia. This study investigated the acute affect of a standardised bilberry extract on
      glucose metabolism in T2D.

      Eight male volunteers with T2D controlling their diabetes by diet and lifestyle alone were
      given a single oral capsule of either 0.47g standardized bilberry extract (36% (w/w)
      anthocyanins) which equates to ∼50 g of fresh bilberries or placebo followed by a
      polysaccharide drink (equivalent to 75 g glucose) in a double blinded cross over intervention
      with a two week washout period.

      This study demonstrates that the ingestion of a concentrated bilberry extract reduces
      postprandial glycaemia and insulin in volunteers with T2D. The most likely mechanism for the
      lower glycaemic response involves reduced rates of carbohydrate digestion and/or absorption.
    

Detailed description: 
      Dietary strategies for alleviating health complications, such as premature vascular disease,
      associated with type 2 diabetes (T2D) and obesity are actively being pursued as alternatives
      to pharmaceutical interventions. The genus Vaccinium (e.g. blueberry, bilberry, cranberry)
      has been used traditionally as a source of folk remedies for established diabetic symptoms.

      Berries from this genus are enriched in anthocyanins, polyphenols recognized for their
      ability to provide and activate cellular antioxidant protection and inhibit inflammatory gene
      expression, activities that may contribute to the efficacy of the Vaccinium genus as
      ameliorators for type 2 diabetes. Consumption of a freeze-dried blueberry beverage for an 8
      week period for example decreased plasma concentrations of the cardiovascular risk factors
      oxidized LDL, malondialdehyde and hydroxynonenal. In another trial, bioactives from
      blueberries improved insulin sensitivity in obese insulin-resistant men and women. In both
      these studies the investigators reported no change in inflammatory markers following
      supplementation although bilberry juice was shown to modulate plasma markers of inflammation
      C-reactive protein and IL-6 in subjects with increased risk of cardiovascular disease. These
      beneficial responses from human studies are supported by data that demonstrate long-term
      beneficial effects of anthocyanins from mouse models of obesity and diabetes.

      There are also a number of studies in vitro and in vivo that suggest that polyphenols
      influence carbohydrate digestion and absorption, resulting in improved postprandial glycaemia
      in the short term. Polyphenols inhibit intestinal alpha glucosidase activity and glucose
      transport in vitro. In association with this, polyphenols administered to rodents suppress
      the elevation of blood glucose concentration after oral administration of mono- and
      di-saccharides. In humans, several studies have examined the effect of polyphenols on the
      post-prandial glycaemic response. In one study a test meal of mixed berry purée with sucrose
      showed a lower plasma glucose concentration after 15-30 min compared with a control matched
      for sugars.

      Overall, evidence suggests that consuming edible berries, particularly from the genus
      Vaccinium, that have high concentrations of anthocyanins could provide a supplementary
      intervention to improve glycaemia in subjects with T2D or impaired glucose tolerance. The
      object of this study was to investigate whether a single supplementation with a standardised
      (36% w/w anthocyanins) concentrated bilberry extract could alter glucose metabolism in
      overweight/obese volunteers with impaired glucose intolerance or T2D compared with a control
      capsule matched for sugars and to explore the possible mechanisms of action.
    

Intervention name(s): Bilberry capsule first, then control cap; Control capsule first then bilberry cap
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): Male subjects aged >40 and <70 years, with type 2 diabetes controlling their diabetes by diet alone closely matched for adiposity as determined by waist circumference (n=8).
Volunteers will be randomised double blinded into two groups (n=4 per group) and given a single capsule of either 0.47 grams of a bilberry extract (mirtoselect provided by Indena S.p.A (http://www.mirtoselect.info/) or a control capsule. Following a two week wash out period the volunteers will be asked to take a second single capsule of either of 0.47 grams of mirtoselect or a control capsule in a cross over study, the opposite of what they took the first time.; Male subjects aged >40 and <70 years, with type 2 diabetes controlling their diabetes by diet alone closely matched for adiposity as determined by waist circumference (n=8).
Volunteers will be randomised double blinded into two groups (n=4 per group) and given a single capsule of either 0.47 grams of a bilberry extract (mirtoselect provided by Indena S.p.A (http://www.mirtoselect.info/) or a control capsule. Following a two week wash out period the volunteers will be asked to take a second single capsule of either of 0.47 grams of mirtoselect or a control capsule in a cross over study, the opposite of what they took the first time.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: anthocyanin; blaeberries; bilberries; blueberries; mirtoselect; glucose AUC