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Trial registered on ANZCTR


Registration number
ACTRN12619001142123
Ethics application status
Approved
Date submitted
14/07/2019
Date registered
16/08/2019
Date last updated
6/02/2020
Date data sharing statement initially provided
16/08/2019
Date results information initially provided
6/02/2020
Type of registration
Prospectively registered

Titles & IDs
Public title
Flour particle size of breads and blood glucose and insulin response
Scientific title
The effect of wheat flour particle size and fibre from wheat on postprandial glycaemia among obese adults aged 55 – 75 not meeting physical activity guidelines: a randomised, controlled, cross-over study.
Secondary ID [1] 298683 0
None
Universal Trial Number (UTN)
U1111-1236-7455
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Type 2 diabetes 313579 0
Condition category
Condition code
Diet and Nutrition 312014 312014 0 0
Other diet and nutrition disorders
Metabolic and Endocrine 312015 312015 0 0
Diabetes

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
This study is a randomised crossover design to measure the blood glucose and insulin responses to breads made with different grain particle size and fibre content. It will be conducted in a research clinic at the University of Otago.

The study includes three bread exposures:
(1) A bread made with finely milled wholegrain flour providing 50 g available carbohydrate (approximately four to five slices), served with 250 mL water
(2) A bread made with coarse stoneground wholegrain flour providing 50 g available carbohydrate (approximately four to five slices), served with 250 mL water
(3) A bread made with fine stoneground wholegrain flour providing 50 g available carbohydrate (approximately four to five slices), served with 250 mL water

Each bread is matched for all macronutrients. They differ in the particle size and the structure of the grain. Each bread will provide 50 g available carbohydrate. Intervention order will be randomised for the four breads. Participants will be able to select the days they wish to attend the clinic for. All treatments will be administered within a 6 week period, with a minimum washout of one day between each treatment.

Key measures:
(1) Blood glucose will be measured via capillary blood taken from a finger prick.
(2) Insulin will be measured via venous blood taken from a cannula placed into a vein in the forearm

Participants will arrive at the research clinic between 7:00 AM and 7:30 AM, having completed a water-only fast for a minimum of 10 hours. A text reminder will be sent to participants 24 hours before, to remind them to adhere to fasting conditions, and to keep their exercise and evening meal consistent before testing mornings. Participants will have been provided with a food and exercise diary to complete for the 24 hours prior to testing. Upon arrival, participants will be fitted with a cannula into a vein in the forearm. This will be performed by a trained health professional (nurse or doctor). They will be given a brief questionnaire to fill out which checks adherence to the study conditions. They will be required to be seated for a minimum of 10 minutes prior to their first (baseline) blood measurements being taken. Two capillary blood samples will be taken (via fingerprick) to assess baseline (fasted) blood glucose, and a 2 mL venous blood sample will be drawn from the cannula to measure insulin at baseline.

Participants will be instructed to consume their test food within 10 minutes, alongside 250 mL water. At 15 minutes following the commencement of eating, a fingerprick blood sample will be taken to measure blood glucose, and a 2 mL sample of venous blood will be drawn from the cannula to measure insulin. These blood samples will be repeated at 30, 45, 60, 90, 120, 150, and 180 minutes. At the end of the 3 hour testing session, participants will be offered a small snack to take away with them.

Each morning of testing will take approximately 3.5 hours of participants' time. The total amount of blood collected each day will be 16 mL.

During the 3-hour testing time, participants will remain seated, except for a bathroom break which will be scheduled at 2 hours post-meal. Participants will be free to take additional bathroom breaks if they require.

The research will be delivered by Evelyn Mete (PhD Student and New Zealand Registered Dietitian), alongside a supervisory team who have many years' experience delivering similar trials.
Intervention code [1] 314957 0
Treatment: Other
Comparator / control treatment
This is a crossover trial, so each participant acts as their own control across all four bread exposures; i.e, each participant's results from one treatment will be compared against their own results for other treatments, because they will have completed all four interventions in randomised order. Any anomalies specific to one participant will be carried over across all four interventions.
Control group
Active

Outcomes
Primary outcome [1] 320716 0
Difference in postprandial blood glucose iAUC (incremental area under the curve).

Capillary blood will be taken via a finger prick, using a sterilized disposable lancet, and blood glucose will be measured by a HemoCue Glucose 201+ Analyzer .

We do not expect any adverse events. Participants may experience some mild discomfort and brief soreness at their fingertips, but this is typically tolerated well.
Timepoint [1] 320716 0
00, 15, 30, 45, 60, 90, 120, 150, 180 minutes after commencement of test food consumption.

t=0 refers to a baseline (fasting) measurement before any food is consumed. t=15 is exactly 15 minutes from the time that the participant begins eating the test food.
Secondary outcome [1] 372595 0
Difference in postprandial insulin iAUC (incremental area under the curve).
Venous blood will be taken via a cannula inserted into a vein in the forearm. The electrochemiluminescence immunoassay “ECLIA” kit (Roche Diagnostics GmbH, D-68298 Mannheim) will be used to measure serum insulin.

We do not expect any adverse events from the cannulation process. Participants may experience some brief discomfort during insertion. The cannula will be inserted by a trained health professional (doctor or nurse).
Timepoint [1] 372595 0
0, 15, 30, 45, 60, 90, 120, 150, 180 minutes after commencement of test food consumption.

t=0 refers to a baseline (fasting) measurement before any food is consumed. t=15 is exactly 15 minutes from the time that the participant begins eating the test food.

Eligibility
Key inclusion criteria
Adults who are aged 55 - 75 years, who have a BMI equal to or greater than 30 kg/m2, and who perform less than 150 minutes of moderate to vigorous exercise per week.
Minimum age
55 Years
Maximum age
75 Years
Gender
Both males and females
Can healthy volunteers participate?
No
Key exclusion criteria
Exclusion criteria include previous diagnosis of diabetes, HbA1c measurement at or over 50 mmol/mol, current infection, taking medication known to affect or control blood glucose, weight change greater than 2% in the previous 3 months, blood donation within previous 12 weeks, avoidance of or allergy to wheat or gluten, and unwillingness/inability to comply with intervention requirements.

Study design
Purpose of the study
Prevention
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Each possible intervention order will be kept in individual opaque envelopes, opened only after each participant has signed their consent form,
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Stata software (version 15.1 for Windows; StataCorp, College Station, Texas) will be used to randomise the intervention order for each participant, using a Williams Square design, so that each intervention is preceded and followed by each other intervention in equal numbers.
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?



Intervention assignment
Crossover
Other design features
N/A
Phase
Not Applicable
Type of endpoint(s)
Efficacy
Statistical methods / analysis
This sample size estimate uses data from a previous cross-over study comparing stoneground flour to wholemeal flour in people with Type 2 Diabetes: the standard deviation of the difference iAUC (incremental area under the curve) was 152 units, with a mean difference iAUC of 97 units. Therefore, a sample size of at least 21 is needed for 80% power to the alpha=0.05 level to detect a difference in iAUC of 100 units between conditions.

Stata 15.1 will be used to perform a mixed effects regression model with blood glucose and insulin iAUC as the outcome, particle size as the predictor, and with participant ID as a random effect. Randomisation order will also be included in the model. Comparisons will be made for particle size, for fibre content, and then to determine whether there is an interaction effect between particle size and fibre on the outcomes. Statistical analyses will be overseen by a biostatistician.

We will aim to recruit 24 participants so that each of the four orders for the Williams Square design has an equal number of participants allocated to it. We intend to re-recruit in the event of participants dropping out.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment outside Australia
Country [1] 21687 0
New Zealand
State/province [1] 21687 0
Otago

Funding & Sponsors
Funding source category [1] 303233 0
Other
Name [1] 303233 0
Riddet Institute
Address [1] 303233 0
Riddet Institute
Massey University
Private Bag 11 222
Palmerston North 4442
Country [1] 303233 0
New Zealand
Primary sponsor type
University
Name
University of Otago
Address
Po Box 56
Dunedin 9010 Otago
Country
New Zealand
Secondary sponsor category [1] 303237 0
None
Name [1] 303237 0
Address [1] 303237 0
Country [1] 303237 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 303779 0
University of Otago Human Ethics Committee (Health)
Ethics committee address [1] 303779 0
1st Floor, Scott/Shand House
90 St David St
Dunedin
9016
Ethics committee country [1] 303779 0
New Zealand
Date submitted for ethics approval [1] 303779 0
08/07/2019
Approval date [1] 303779 0
13/08/2019
Ethics approval number [1] 303779 0
H19/098

Summary
Brief summary
Eating wholegrain foods can reduce the risk of developing diseases such as type 2 diabetes and cardiovascular disease. However, the range of wholegrain foods that are commercially available are made with a variety of processing methods – ranging from minimally processed, primarily intact grains, to the finely milled flour which is commonly used in commercial breads. Some evidence suggests that the extent of the grain processing may affect humans’ physiological responses to their consumption, but this is not yet fully understood.

Our study aims to investigate the effect of wheat flour particle size and grain structure in breads on acute metabolic response in adults who have risk factors for developing type 2 diabetes.

We will test participants’ blood glucose and insulin responses to each of the test breads over 3 hours. These results will help to identify whether a specific processing method for breads may help to reduce the risk of developing type 2 diabetes.

We hypothesise that a coarser flour particle size in bread and more intact structure of the grain will result in a significantly different postprandial blood glucose response than a finer flour particle size, among adults at risk of developing metabolic disease.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 94774 0
Ms Evelyn Mete
Address 94774 0
University of Otago
Department of Human Nutrition
PO Box 56
Dunedin Otago 9010
Country 94774 0
New Zealand
Phone 94774 0
+64 3 479 7959
Fax 94774 0
Email 94774 0
evelyn.mete@postgrad.otago.ac.nz
Contact person for public queries
Name 94775 0
Prof Jim Mann
Address 94775 0
University of Otago
Dunedin School of Medicine
PO Box 56
Dunedin 9054
New Zealand
Country 94775 0
New Zealand
Phone 94775 0
+64 3 470 9336
Fax 94775 0
Email 94775 0
jim.mann@otago.ac.nz
Contact person for scientific queries
Name 94776 0
Prof Jim Mann
Address 94776 0
University of Otago
Dunedin School of Medicine
PO Box 56
Dunedin 9054
New Zealand
Country 94776 0
New Zealand
Phone 94776 0
+64 3 470 9336
Fax 94776 0
Email 94776 0
jim.mann@otago.ac.nz

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No
No/undecided IPD sharing reason/comment
What supporting documents are/will be available?
No other documents available
Summary results
Have study results been published in a peer-reviewed journal?
No
Other publications
Have study results been made publicly available in another format?
No
Results – basic reporting
Results – plain English summary