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Trial registered on ANZCTR


Registration number
ACTRN12610000484044
Ethics application status
Approved
Date submitted
7/06/2010
Date registered
11/06/2010
Date last updated
12/07/2012
Type of registration
Retrospectively registered

Titles & IDs
Public title
Validity of the concept of glycemic load as a predictor of postprandial glucose and insulin responses in lean, healthy adults.
Scientific title
To determine the degree of association between calculated glycemic load and glucose and insulin responses in healthy subjects consuming iso-energetic portions of single foods and mixed meals
Secondary ID [1] 251732 0
Nil
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Type 1 diabetes 257341 0
Type 2 diabetes 257342 0
Condition category
Condition code
Metabolic and Endocrine 257484 257484 0 0
Diabetes

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
1000 kJ portion of 121 single foods were selected, tested and grouped into ten food categories : dairy products, breakfast cereals, bakery products, fruits and fruit juices, vegetables, snack foods, carbohydrate-rich foods, protein-rich foods, fat-rich foods, beverages and alcoholic drinks. Separate groups of healthy subjects (n = 10 - 13 for each group) were recruited to test each category of foods. Each participant acted as their own control, testing the reference food (either white bread or glucose) on two separate occasions. Then the participant consumed the testing foods in a food category on separate mornings. The wash-out period between test sessions was at least one day.

2000 kJ portion of 13 mixed meals were consumed by two groups of healthy subjects on separate testing days. One group (n = 11) consumed 6 meals and the other group (n = 10) consumed 7 meals. The reference meal of white bread was tested at the beginning and end of the whole test sessions. The wash-out period between test sessions was at least one day.


Foods and meals varied widely in macronutrients, fiber and glycemic load and were representative of common energy source contributed to the western diets. Finger-prick blood samples were collected before the meal (0 min) and 15, 30, 45, 60, 90, 120 min after the start of the meal and assayed for glucose and insulin.
Intervention code [1] 256455 0
Treatment: Other
Intervention code [2] 256634 0
Prevention
Comparator / control treatment
Iso-energetic portions of either glucose or white bread were consumed twice as the reference food and the average glucose or insulin responses were used as the basis of comparison with all other foods or meals.
Control group
Active

Outcomes
Primary outcome [1] 258404 0
The correlations between observed glucose response and calculated glycemic load (GL) in 121 single foods and 13 mixed meals respectively.

The observed blood glucose response for each test food or meal relative to the reference food was described as a glucose score (GS). Specifically, for each subject, finger-prick blood samples were collected and assayed for glucose at regular intervals over 2 hours after the meal. Then the glucose incremental area under the 120-min response curve (AUC) was calculated according to the trapezoidal method and compared with the average reference AUC.The mean +/- standard error of the mean (SEM) for a group of subjects was the reported observed GS to the test food or meal.

The GL was calculated as published Glycemic Index values x available carbohydrate content per 1000 kJ portion for each food or meal.

Linear regression analysis was used to test associations between GS and GL, with stepwise regressions used to examine the extent to which GL accounted for the variability of GS.
Timepoint [1] 258404 0
Baseline (0 min), and at 5, 15, 30, 45, 60, 90 and 120 minutes after starting eating the food or meal.
Primary outcome [2] 258405 0
The correlations between observed insulin response and calculated glycemic load (GL) in 121 single foods and 13 mixed meals respectively.

The observed blood insulin response for each test food or meal relative to the reference food was described as a Food Insulin Index (FII). Specifically, for each subject, finger-prick blood samples were collected and assayed for insulin at regular intervals over 2 hours after the meal. Then the insulin incremental area under the 120-min response curve (AUC) was calculated according to the trapezoidal method and compared with the average reference AUC.The mean (+/- SEM) for a group of subjects was the reported observed FII to the test food or meal.

The GL was calculated as published Glycemic Index values x available carbohydrate content per 1000 kJ portion for each food or meal.

Linear regression analysis was used to test associations between FII and GL, with stepwise regressions used to examine the extent to which GL accounted for the variability of FII
Timepoint [2] 258405 0
Baseline (0 min), and at 5, 15, 30, 45, 60, 90 and 120 minutes after starting eating the food or meal.
Secondary outcome [1] 264155 0
The correlations between observed glucose response and macronutrients, Glycemic Index (GI) and fiber in 121 single foods and 13 mixed meals.

The observed blood glucose response for each test food or meal relative to the reference food was described as a glucose score (GS). Specifically, for each subject, finger-prick blood samples were collected and assayed for glucose at regular intervals over 2 hours after the meal. Then the glucose incremental area under the 120-min response curve (AUC) was calculated according to the trapezoidal method and compared with the average reference AUC.The mean (+/- SEM) for a group of subjects was the reported observed GS to the test food or meal.

GI values were derived from the published GI tables.

Linear regression analysis was used to test associations, with stepwise regressions used to examine the extent to which the different predictors accounted for the variability of GS.
Timepoint [1] 264155 0
Baseline (0 min), and at 5, 15, 30, 45, 60, 90 and 120 minutes after starting eating the food or meal.
Secondary outcome [2] 264156 0
The correlations between observed insulin response and macronutrients, Glycemic Index (GI) and fiber in 121 single foods and 13 mixed meals respectively.

The observed blood insulin response for each test food or meal relative to the reference food was described as a Food Insulin Index (FII). Specifically, for each subject, finger-prick blood samples were collected and assayed for insulin at regular intervals over 2 hours after the meal. Then the insulin incremental area under the 120-min response curve (AUC) was calculated according to the trapezoidal method and compared with the average reference AUC.The mean (+/- SEM) for a group of subjects was the reported observed FII to the test food or meal.

GI values were derived from the published GI tables.

Linear regression analysis was used to test associations between FII and different predictors including macronutrients, GI and fiber, with stepwise regressions used to examine the extent to which the different predictors accounted for the variability of FII
Timepoint [2] 264156 0
Baseline (0 min), and at 5, 15, 30, 45, 60, 90 and 120 minutes after starting eating the food or meal.

Eligibility
Key inclusion criteria
non-smoking, aged 18-40 years, stable body weight, Body Mass Index (BMI) 19-25 kg/m2, normal glucose tolerance, no prescription medication other than oral contraceptives, no known food allergy, regular physical activity, normal dietary habits, and no history of eating disorders
Minimum age
18 Years
Maximum age
40 Years
Sex
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Eating disorders, individuals using medication that may influence blood glucose profiles, food allergy, abnormal glucose tolerance

Study design
Purpose of the study
Treatment
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
For each food category, 10 - 13 lean, healthy subjects were recruited from the student population of the University of Sydney. Each group of subjects only tested one food category.

The flyer which was approved by the Human Research Ethics Committee of Sydney Unversity was advertised in the campus. The administration officer who was "off site" assessed whether the participant met the criteria and allocated him or her into a certain food category.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Subjects acted as their own control, testing the reference food and test foods in a random order on separate occasions. A randomisation digit- table from a statistic book will be used to randomise the order of test food for each subject.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?



Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
1/09/1998
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
150
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 256946 0
University
Name [1] 256946 0
Sydney University Glycemic Index Research Service
Country [1] 256946 0
Australia
Funding source category [2] 256947 0
University
Name [2] 256947 0
Harvard Public Health School
Country [2] 256947 0
United States of America
Primary sponsor type
University
Name
Sydney University Glycemic Index Research Service
Address
Level 4, Molecular and Microbial Biosciences (MMB) building, G08 The University of Sydney, NSW 2006
Country
Australia
Secondary sponsor category [1] 256209 0
University
Name [1] 256209 0
Harvard Public Health School
Address [1] 256209 0
651 Huntington Avenue, Boston, Massachusetts 02115
Country [1] 256209 0
United States of America

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 258949 0
Human Research Ethics Committee, the University of Sydney
Ethics committee address [1] 258949 0
Jane Foss Russell Building - G02 The University of Sydney NSW 2006
Ethics committee country [1] 258949 0
Australia
Date submitted for ethics approval [1] 258949 0
Approval date [1] 258949 0
04/08/1998
Ethics approval number [1] 258949 0
98/8/4

Summary
Brief summary
The study aimed to determine the degree of association between calculated glycemic load (GL) and glucose and insulin responses in healthy subjects consuming iso-energetic portions of single foods and mixed meals. 10 groups of healthy subjects consumed 1000 kJ portions of 121 single foods in 10 food categories and other 2 group of subjects consumed 2000 kJ of 13 mixed meals. Foods and meals varied widely in macronutrient content, fibre and GL. Glycaemia and insulinemia were quantified as incremental area under the curve relative to a reference food (=100). Then the results were correlated with GL to determine the extent that GL can explain the variability of glucose and insulin responses in healthy subjects.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 31146 0
Address 31146 0
Country 31146 0
Phone 31146 0
Fax 31146 0
Email 31146 0
Contact person for public queries
Name 14393 0
Jiansong Bao
Address 14393 0
Room 453, Human Nutrition Unit, Biochemistry Building G08, The University of Sydney, NSW 2006
Country 14393 0
Australia
Phone 14393 0
+61 2 93514672
Fax 14393 0
+61 2 93516022
Email 14393 0
[email protected]
Contact person for scientific queries
Name 5321 0
Professor Jennie BrandMiller
Address 5321 0
Room 472, Human Nutrition Unit, School of Molecular and Microbial Biosciences, G08, University of Sydney, NSW 2006
Country 5321 0
Australia
Phone 5321 0
+61 2 9351 3759
Fax 5321 0
+61 2 9351 6022
Email 5321 0
[email protected]

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No Supporting Document Provided



Results publications and other study-related documents

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