Effect of a Beverage Comprised of Compounds From Olives on Post-prandial Blood Glucose Responses in Healthy Volunteers
Keywords
Abstract
Description
The world health organisation has reported that over 220 million people suffer from diabetes worldwide and that by the year 2030, this number will be doubled. The WHO also reports that in 2004, about 3.4 million people died from high blood sugar. About 90% of all diabetes cases is due to type II diabetes. Type 2 diabetes is largely due to overweight and lack of physical activity characterised by high glucose levels (hyperglycaemia).
In the human diet, the source of blood glucose is carbohydrates. Dietary carbohydrate is important to maintain glycaemic homeostasis and provides the most of the energy in the diets of most people. The control of blood glucose is a hormonal process and it is very important to human physiology. Hormonal processes involve the release of insulin from the β- cells of the pancreatic cells which stimulates the uptake of glucose after a meal, to other tissues either for utilisation (glycolysis) or to be stored in the liver as glycogen (glycogenesis). When blood glucose falls below normal, glucagon is secreted from the pancreatic α-cells and it promotes liver glucose production by inducing the generation of glucose from non-carbohydrate substrates such as amino and fatty acids (gluconeogenesis) and the generation of glucose from glycogen (glycogenolysis).
When the glucose homeostasis hormonal control fails, it entails high blood glucose levels (postprandial hyperglycaemia) which can lead to metabolic syndrome which includes obesity, impaired glucose tolerance (IGT), hypertension and dyslipidemia. Disturbance of glucose homeostasis can also lead to other symptoms such as inflammation and oxidative stress at the whole body level as well as disturbances of the functionality in several organs as well as diabetes. Therefore, as much as carbohydrates are required in the human body as a major source of energy, too much in the diet can have adverse health effects especially the one with high glycaemic effect.
The proposed mechanism adapted from Aston, 2006 of how carbohydrates may affect human health is that when there is a continual presence of high glycaemic index foods in the diet, this gives rise to postprandial glucose rise as well as high insulin demand to act on the high blood glucose levels in the blood. Postprandial glucose rise and high insulin demand may lead to insulin resistance which is the major component of metabolic syndrome. High insulin demand may also lead to β-cell failure which may also result in hyperglycaemia which is also a cause of insulin resistance. Insulin resistance and hyperglycaemia are risk factors for metabolic syndrome and diabetes type 2.
Scientific evidence suggest that postprandial hyperglycaemia in humans has a major role to play in health priorities like type 2 diabetes and blood glucose control. It has been reported that about 90% of all diabetes cases consist of type 2 diabetes. Apart from type I and type 2 diabetes, there are other related conditions which include pre-diabetes (impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) as well as metabolic syndrome (obesity, hypertension and insulin resistance). It has been reported that pre-diabetes and metabolic syndrome increases the risk of developing cardiovascular disease and diabetes mellitus. The glycaemic index was originally proposed with the aim of managing diabetes. However, recent studies have shown that the GI has potential in the prevention of type 2 diabetes as well as in the treatment of metabolic syndrome. Research has shown that high GI diets are associated with increased risk of developing type 2 diabetes. More research has shown that high GI diet is associated with a number of abnormalities like increased metabolic syndrome and insulin resistance. In the same way, a low GI diet is said to improve insulin sensitivity but more research is needed to support this. A few studies have shown this to be the case. However it was observed that it was difficult to know whether this was as a result of improved insulin sensitivity, or improved insulin secretion or due to reduced rate of glucose absorption.
Potential solution having anything in the diet that can either slow down the digestion and absorption of carbohydrates can help reduce the risk. Among others, two potential solutions are that of consumption of low glycaemic index foods or having ingredients in the diet that can reduce the glycaemic index of foods as well as postprandial blood glucose levels. The presence of inhibiting components in the diet that can reduce postprandial glucose can also be a solution to reducing the risk. Drugs like acarbose are currently used in some countries for the management of type 2 diabetes which act by inhibiting carbohydrate digestive enzymes. However, the use of acarbose has side effects such as nausea, flatulence and diarrhoea. It has been reported that polyphenols also have the potential to inhibit the rise in blood glucose by hindering the rapid absorption of glucose.
A recent review has reported that research using animal models as well as a limited number of human studies, have shown that polyphenols and polyphenol rich foods or beverages have the potential to affect postprandial glycaemic responses and fasting glycaemia as well as an improvement of acute insulin secretion and sensitivity. Other possible mechanisms as reported in the review include pancreatic β- cells stimulation to secrete insulin as well as activation of insulin receptors, modulation of the release of glucose from the liver as well as of intracellular signalling pathways and gene expression.
Another recent review concluded that it is very possible that the effects of polyphenols in the diet will affect glycaemic index of foods as well as postprandial glucose responses in humans. The two mechanisms highlighted by which this can be achieved being the inhibition of sugar metabolising enzymes as well as transporters. This potential action of polyphenols can thus be compared to that of acarbose which acts by the same mechanism and research in chronic intervention studies has shown that it reduces diabetes risk.
This research will involve the use of soluble olive powder as a source of polyphenols to determine its effects on the glycaemic response when consumed together with a carbohydrate source. Four interventions will be carried out as follows:
1. White bread as source of carbohydrate
2. Whole meal bread as source of carbohydrate
3. Glucose as source of carbohydrate
4. Sucrose as source of carbohydrate
5. White bread as source of carbohydrate but with 3 days high fat diet prior to the study visit.
6. White bread as source of carbohydrate but with 3 days high carbohydrate diet prior to the study visit.
The study was approved by the University of Leeds Mathematical and Physical Sciences (MAPs) ethical committee with application number MEEC15-044. At least 10 volunteers will be recruited for each intervention (white bread, whole bread, glucose, sucrose, 3 days high fat diet, 3 days high carbohydrate diet). The volunteers will be screened for their fasting blood glucose level. They will need to be healthy and their fasting blood glucose levels should fall within the healthy range of 4.3-5.9mmol/L.
The volunteers are scheduled to attend 3 visits. During each visit, the volunteer comes fasted in the morning and the fasting blood glucose is measured by the use of a glucometer. The volunteer is then given a test meal which will be randomized and blood glucose will be measured at 15, 30, 45, 60, 90, 120,150 and 180 minutes after the first bite of the test meal. The results will be used to plot the area under the curve and results obtained after consuming test meals will be compared to those obtained after consumption of control meals.
THE SIX DIFFERENT INTERVENTIONS MAY OR MAY NOT BE COMBINED FOR PURPOSES OF PUBLISHING RESULTS. EACH INTERVENTION WILL AIM TO HAVE AT LEAST 10 PARTICIPANTS.
Dates
Last Verified: | 03/31/2018 |
First Submitted: | 03/21/2017 |
Estimated Enrollment Submitted: | 03/21/2017 |
First Posted: | 03/27/2017 |
Last Update Submitted: | 04/16/2018 |
Last Update Posted: | 04/17/2018 |
Actual Study Start Date: | 06/30/2016 |
Estimated Primary Completion Date: | 07/31/2017 |
Estimated Study Completion Date: | 08/31/2017 |
Condition or disease
Intervention/treatment
Other: Control (study 1)
Other: Test (study 1)
Other: Control (study 2)
Dietary Supplement: Test (study 2)
Other: Control (study 3)
Dietary Supplement: Test (study 3)
Other: Control (study 4)
Dietary Supplement: Test (study 4)
Other: Control (study 5)
Other: Test (study 5)
Other: Control (study 6)
Other: Test (study 6)
Other: Control (study 7)
Other: Test (study 7)
Phase
Arm Groups
Arm | Intervention/treatment |
---|---|
Placebo Comparator: Control (study 1) Control will be 50g glucose dissolved in 200 mL water | Other: Control (study 1) Control meal will comprise of 50 g glucose dissolved in 200 ml water, to which the response of the test meals will be compared to |
Experimental: Test (study 1) The test meals will comprise 50 g glucose plus 50 mg oleuropein from olives dissolved in 200 mL water | Other: Test (study 1) The test meal will comprise 50 g glucose in 200 ml water plus 50 mg oleuropein from olives |
Placebo Comparator: Control (study 2) Control will be white bread (109 g) to give 50 g available carbohydrates with 200 mL water | Other: Control (study 2) Control meal will comprise 109 g white bread to give 50 g available carbohydrate and 200 ml water, to which the response of the test meals will be compared to |
Experimental: Test (study 2) The test meals will comprise 109 g white bread plus 50 mg oleuropein from olives | Dietary Supplement: Test (study 2) The test meal will comprise 109 g white bread plus 50 mg oleuropein from olives dissolved in 200 ml water |
Placebo Comparator: Control (study 3) Control will be whole-meal bread (132 g) to give 50 g available carbohydrates with 200 mL water | Other: Control (study 3) Control meal will comprise whole-meal bread to give 50 g available carbohydrate and 200 ml water, to which the response of the test meals will be compared to |
Experimental: Test (study 3) The test meals will comprise whole-meal bread (132 g) with 50 mg oleuropein dissolved in 200 mL water | Dietary Supplement: Test (study 3) The test meal will comprise whole-meal bread plus 50 mg oleuropein from olives dissolved in 200 ml water |
Placebo Comparator: Control (study 4) Control will be 50 g sucrose dissolved in 200 mL water | Other: Control (study 4) Control meal will comprise 50 g sucrose in 200 ml water, to which the response of the test meals will be compared to |
Experimental: Test (study 4) The test meals will comprise 50 mg oleuropein and 50 g sucrose dissolved in 200 ml water | Dietary Supplement: Test (study 4) The test meal will comprise 50 g sucrose in 200 ml water plus 50 mg oleuropein from olives |
Placebo Comparator: Control (study 5) Control will be 25 g sucrose dissolved in 200 mL water | Other: Control (study 5) Control meal will comprise 25 g sucrose in 200 ml water, to which the response of the test meals will be compared to |
Experimental: Test (study 5) The test meals will comprise 160 mg oleuropein and 25 g sucrose dissolved in 200 ml water | Other: Test (study 5) The test meal will comprise 25 g sucrose in 200 ml water plus 160 mg oleuropein from olives |
Placebo Comparator: Control (study 6) Normal diet 3 days prior to study visit with 109 g bread with 200 ml water on study visit | Other: Control (study 6) Normal diet 3 days prior to the visit day and 109 g bread with 200 ml water on the study day |
Experimental: Test (study 6) High carbohydrate diet 3 days prior to study visit with 109 g bread with 200 ml water on study visit | Other: Test (study 6) High carbohydrate diet (23% fat, 55% carbohydrates and 22% protein) 3 days prior to the visit day and 109 g bread with 200 ml water on the study day |
Placebo Comparator: Control (study 7) Normal diet 3 days prior to study visit with 109 g bread with 200 ml water on study visit | Other: Control (study 7) Normal diet 3 days prior to the visit day and 109 g bread with 200 ml water on the study day |
Experimental: Test (study 7) High fat diet 3 days prior to study visit with 109 g bread with 200 ml water on study visit | Other: Test (study 7) High fat diet (44% fat, 34% carbohydrates and 22% protein) 3 days prior to the visit day and 109 g bread with 200 ml water on the study day |
Eligibility Criteria
Ages Eligible for Study | 18 Years To 18 Years |
Sexes Eligible for Study | All |
Accepts Healthy Volunteers | Yes |
Criteria | Inclusion Criteria: Measured - Fasting plasma glucose between 3.9 -5.6 mmol/L Self-assessed - Apparently healthy - Not diabetic - Not pregnant nor lactating - Not on special diet (for loosing weight) - Not on long term prescribed medication Exclusion Criteria: Measured - Fasting plasma glucose >5.6 mmol/L Self-assessed - Not healthy - Diabetic - Pregnant or lactating - On special diet (for loosing weight) - On long term prescribed medication - Smoker - Diabetic - Allergic to olives |
Outcome
Primary Outcome Measures
1. Incremental area under the glucose curve [9 months]