Effects of Carbohydrase-inhibiting Polyphenols on Glycaemic Response in Vivo

Summary

Consumption of carbohydrate containing foods or sugary drinks brings about changes to the blood glucose levels. After a meal or drink, blood glucose levels rise until it reaches a peak concentration usually after 30 minutes. When the body senses the increase in blood glucose, a hormonal process involving insulin takes place to ensure that the glucose is taken up from the blood for storage and where it is needed for energy in the body. This process then brings about a decrease in the concentration of glucose until it reaches approximately the starting concentration. The original concentration of glucose is attained approximately 2 hours after eating or drinking a carbohydrate food or sugary drink respectively.

Different carbohydrates and sugary drinks have different effects on blood glucose response depending on the amount as well as the type of carbohydrate. Those that give rise to a high glucose response compared to a reference carbohydrate (usually glucose) are said to be high glycaemic index (GI) foods and those with a lower glucose response compared to a reference carbohydrate (usually glucose) are said to be low glycaemic index (GI) foods.(1)

Research has shown that diets that give rise to a high glucose response are associated with a number of abnormalities like increased metabolic syndrome (2). Metabolic syndrome mostly comprises of insulin resistance and glucose intolerance which gives an increased risk of type 2 diabetes. (3) It also gives rise to other conditions like high blood pressure (arterial hypertension), elevated blood insulin levels (hyper-insulinemia), elevated amounts of fat in the liver (fatty hepatosis) and elevated amounts of lipids in the blood (dyslipidemia). After type 2 diabetes become clinically apparent, the risk of cardiovascular disease also rises. (4) Research has also shown that foods/drinks which raise blood glucose levels gradually (low GI) rather than rapidly (high GI) have health benefits which include reducing the risk of metabolic syndrome (5). In vitro studies have shown that polyphenols found in fruits, vegetables and plant based foods have a positive effect on carbohydrate metabolism and can lower the blood glucose levels. (6)

This research will determine whether the presence of polyphenols in the diet has any lowering effect on the blood glucose levels and hence the glycaemic index of foods. This will be determined by asking volunteers to consume polyphenol rich drink/food together with white bread and determine the glycaemic response. The GI of bread will be determined initially as a reference.

Analysis will be done by measuring blood glucose response to white bread alone as reference and then to white bread with test sample containing polyphenols and then determine GI and see how the GI of bread will be affected. Other analyses to be done are plasma insulin, glucagon, gastric inhibitory polypeptide (GIP) and glucagon like peptides-1 (GLP-1) as they all relate to glycaemic response.

Study hypothesis is that glucose metabolism will be affected.

NOTE:

1. Only healthy participants undertook the study (Hence metabolic syndrome participants not part of the study)
2. Only glucose and insulin were analysed in the plasma (hence GIP, GLP-1 and glucagon not part of end points)

Conditions

• Hyperglycaemia

Interventions

OTHER

Reference food

Reference food will be used to which test food samples will be compared to.

OTHER

Test food dose 1

Will contain low dose of a mixture of polyphenols in addition to the reference food

OTHER

Test food dose 2

Will contain high dose (twice of the low dose) of a mixture of polyphenols in addition to the reference food

Sponsors & Collaborators

• University of Leeds

  lead OTHER

Principal Investigators

• Gary Williamson · University of Leeds

• Hilda Nyambe · University of Leeds

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

SINGLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

75 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2014-08-31

Primary Completion

2015-03-31

Completion

2015-09-30

Countries

• United Kingdom

Study Locations