A Single Supplement of a Standardised Bilberry Extract Modifies Glycaemic Response

University of Aberdeen

Status: Completed

Conditions: Type 2 Diabetes

Treatments: Dietary Supplement: Bilberry capsule first, then control cap; Dietary Supplement: Control capsule first then bilberry cap

Study type: Interventional

Funder types: Other

Identifiers

NCT01245270

REC 10/S0801/54

902

Details and patient eligibility

About

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.

Full 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.

Enrollment: 8 patients

Sex: Male

Ages: 40 to 70 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Male subjects
• Aged >40 and <70
• Clinical diagnosis of Type 2 diabetes controlling their diabetes by diet alone
• All subjects must live in the Aberdeenshire area of Scotland

Exclusion criteria

• Medical exclusion criteria
• Clinical diagnosis of thromboembolic or coagulation disease
• Clinical diagnosis of unregulated thyroid disease
• Clinical diagnosis of kidney disease
• Clinical diagnosis of severe gastrointestinal disorders
• History of Alcohol or any other substance abuse

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Crossover Assignment

Masking: Double Blind

---

8 participants in 2 patient groups

Bilberry capsule first, then control cap

Experimental group

Description:

Volunteers will be given a single capsule of 0.47 grams of mirtoselect (a concentrated bilberry extract) followed by a 14 day washout period then a single control placebo capsule. First Intervention (1 day), Washout (14 days), Second Intervention (1 day)

Treatment:

Dietary Supplement: Bilberry capsule first, then control cap

Control capsule first, then bilberry cap

Experimental group

Description:

Volunteers will be given a single control placebo capsule followed by a 14 day washout period the a single capsule of 0.47 grams of mirtoselect (a concentrated bilberry extract) First Intervention (1 day), Washout (14 days), Second Intervention (1 day)

Treatment:

Dietary Supplement: Control capsule first then bilberry cap