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Trial registered on ANZCTR


Trial ID
ACTRN12617000502336
Ethics application status
Approved
Date submitted
28/03/2017
Date registered
6/04/2017
Date last updated
14/03/2018
Type of registration
Prospectively registered

Titles & IDs
Public title
A human intervention trial to test the effect of potatoes on blood glucose concentrations.
Scientific title
Glycaemic potency of potatoes: A randomised, repeated measures, human intervention study in healthy volunteers.
Secondary ID [1] 291510 0
The New Zealand Institute for Plant and Food Research core funding programme: Project code, P/274067/01.
Universal Trial Number (UTN)
U1111-1194-5541
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Diabetes
302637 0
Metabolic disorders 302638 0
Condition category
Condition code
Metabolic and Endocrine 302155 302155 0 0
Diabetes
Metabolic and Endocrine 302156 302156 0 0
Metabolic disorders

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
A randomised repeated measures design will be used in which each participant receives all diets once, with the order of the diets randomised for each participant.
The test foods will be as follows:
1. Glucose: 50 g (Reference) dissolved in 180 ml water
2. Sliced and boiled Agria potato (50 g carbohydrate)
3. Sliced and boiled Crop 39 potato (50 g carbohydrate)
Each test food will be tested once in each participant and will have a minimum of a 48 hour wash out period between each treatment.
All test foods will contain 50 g carbohydrate. The exact available carbohydrate content of all diets will be determined by in vitro digestive analysis prior to calculating the results. All of the potato to be used will be roughly equal in size. They will be brushed, sliced and portioned to achieve a serving of 50 g carbohydrate. Prior to feeding to the participant the potato slices will be boiled to soften. The participants will be given 200 ml of water to be consumed with all diets.
Volunteers will be asked to fast for 12 h prior to each test day and refrain from extreme physical activity. On each test day the volunteers will be seated and asked to remain so for the duration of the test, they continue work, if practical to do so, at the testing location. Once each participant is relaxed and comfortable a baseline blood sugar measurement will be taken in duplicate for that day. Each participant will then be given a test food and instructed to consume the whole amount within a ten-minute period. Blood glucose testing will be timed from the start of food consumption by finger prick sampling of capillary blood at 15 min intervals in the first hour and then at 30 min intervals until 180 min has elapsed. Samples will be thus be collected at 0 (baseline x 2), 15, 30, 45, 60, 90, 120, 150 and 180 minutes. Two analyses will be made from each blood sample. Blood glucose will be measured immediately using a HemoCue (registered trademark) blood glucose meter. The remaining capillary blood sample will be drawn into a Z gel serum Microvette (registered trademark) microtube designed for capillary blood collection, centrifuged and stored at -80 degrees for later insulin analysis. At 0, 15, 60, 120 and 180 min appetite will be assessed using a questionnaire containing recommended visual analogue scales for self-reported appetite in healthy adults (Charlot, 2013).

Charlot, K. and D. Chapelot, Energy compensation after an aerobic exercise session in high-fat/low-fit and low-fat/high-fit young male subjects. Br J Nutr, 2013. 110(6): p. 1133-42.
Intervention code [1] 297613 0
Prevention
Intervention code [2] 297614 0
Lifestyle
Comparator / control treatment
Glucose reference (50 g)
Control group
Active

Outcomes
Primary outcome [1] 301584 0
To determine the glycaemic potency of two potato varieties: Agria and Crop 39 using blood glucose concentrations.
Timepoint [1] 301584 0
Measure blood glucose concentrations at 0, 15, 30, 45, 60, 120, 150 and 180 mins after a serving of two potato varieties and a glucose reference (equivalent 50 g carbohydrate). Three test sessions will be conducted over a period of two weeks, with at least a 48 hour wash out between test sessions.
Primary outcome [2] 301585 0
Determine glycaemic index of two potato varieties: Agria and Crop 39 using blood glucose concentrations.
Timepoint [2] 301585 0
Measure blood glucose concentrations at 0, 15, 30, 45, 60, 120, 150 and 180 mins after a serving of two potato varieties and a glucose reference (equivalent 50 g carbohydrate). Three test sessions will be conducted over a period of two weeks, with at least a 48 hour wash out between test sessions.
Secondary outcome [1] 333186 0
Analyse blood insulin responses following the consumption of two potato varieties: Agria and Crop 39.
Timepoint [1] 333186 0
Measure blood insulin concentrations at 0, 15, 30, 45, 60, 120, 150 and 180 mins after a serving of two potato varieties and a glucose reference (equivalent 50 g carbohydrate). Three test sessions will be conducted over a period of two weeks, with at least a 48 hour wash out between test sessions.
Secondary outcome [2] 333187 0
Measure satiety with a visual analogue scale questionaire following consumption of two potato varieties: Agria and Crop 39.
Timepoint [2] 333187 0
At 0. 15, 60, 120 and 180 min appetite will be assessed using a questionnaire containing recommended visual analogue scales for self-reported appetite in healthy adults. Three test sessions will be conducted over a period of two weeks, with at least a 48 hour wash out between test sessions.

Eligibility
Key inclusion criteria
Age: Aged between 18 and 65.
Sex: Male or female.
Glucose tolerance: No history of diabetes or evidence of glucose intolerance in a preliminary screening test.
BMI: Volunteers have a body mass index between 18 and 30 kg/m2
Health: Healthy as gauged by self-assessment and result on the General Health Questionnaire.
Agreement: Subject having given written informed consent to comply with the conditions of the trial.
Minimum age
18 Years
Maximum age
65 Years
Gender
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Glucose tolerance: Any history of diabetes or evidence of glucose intolerance in a preliminary test (greater than or equal to 6.0mmol/l fasting glucose, International Diabetes Federation recommendation).
Non-fasting: Having consumed anything apart from water in the twelve hours prior to the test.
Allergic or intolerant to potatoes.

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 participants will be assigned an identification number, including those who fail the screening procedure.
Participants who pass the screening procedure will be allocated numbers after the recruitment process is finished. Therefore, the recruiter does not know which treatment the participant will start with.
Each participant receives all treatments in random order rather than being allocated to one group. The order will be determined by computer randomisation.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
The order of the diets for each subject (n=15-20) will be determined by 15-20 computer randomisations of the numbers 1-3.
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?



Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint(s)
Efficacy
Statistical methods / analysis
Groups will be compared in terms of response amplitude, time to baseline and incremental area under the blood glucose response curve by comparison of treatments. A registered statistician at Plant & Food Research will conduct the statistical analysis.
Participant numbers are based on the number specified in the standard protocol for glycaemic index (GI) determination and on a recent trial of the effects of kiwifruit on blood glucose, in which n = 20 was enough to detect significant differences between diets.

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] 8769 0
New Zealand
State/province [1] 8769 0
Manawatu

Funding & Sponsors
Funding source category [1] 295999 0
Government body
Name [1] 295999 0
The New Zealand Institute for Plant and Food Research
Address [1] 295999 0
Private Bag 11600, Palmesrton North, New Zealand, 4442
Country [1] 295999 0
New Zealand
Primary sponsor type
Government body
Name
The New Zealand Institute for Plant and Food Research
Address
Private Bag 11600, Palmerston North, New Zealand, 4442
Country
New Zealand
Secondary sponsor category [1] 294885 0
None
Name [1] 294885 0
Address [1] 294885 0
Country [1] 294885 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 297260 0
Health and Disability Ethics commitee
Ethics committee address [1] 297260 0
Ministry of Health
Health and Disability Ethics Committees
PO Box 5013
Wellington 6140
Ethics committee country [1] 297260 0
New Zealand
Date submitted for ethics approval [1] 297260 0
17/05/2017
Approval date [1] 297260 0
08/06/2017
Ethics approval number [1] 297260 0
17/NTB/88

Summary
Brief summary
Our research has shown that potatoes vary in glycaemic index (GI). This index is used to rank carbohydrates according to how they affect blood glucose. Low GI foods release glucose slowly into the blood stream, whilst high GI foods release glucose rapidly into the blood steam. High GI foods can contribute to development of metabolic diseases, such as obesity and diabetes. Substituting a high GI potato with a low GI potato offers a valuable alternative for people with impaired glucose tolerance, such as those with higher blood glucose levels after fasting, which suggests the body is not managing glucose well. We would like to test some different varieties of potatoes and their effects on blood glucose and insulin (a hormone that helps remove excess glucose from the blood).
The primary aim of this study is to determine the effects of two potato varieties on blood glucose concentrations. The two potato varieties used in this trial (Agria and Crop 39), have been selected for possessing a high (Agria) and low (Crop 39) GI when estimated using laboratory techniques. We aim to determine the actual GI of Agria and Crop 39 by feeding the potatoes to participants and measuring blood glucose concentrations. We will also look at the effects of the potatoes on blood Insulin, which is a hormone that helps control the levels of glucose in our blood.
The study is a randomized repeated measures design which means participants will be asked to consume three test foods, one per testing session, in random order. The foods will be: (1) glucose (50 g), (2) Agria potato (about 250 g, sliced and boiled), (3) Crop 39 potato (about 250 g, sliced and boiled).
Individuals will be chosen to participate in the study if they are within the age bracket (18-65) and considered to be generally healthy.
During the study participants will be required to refrain from eating after 8 pm (water only), and avoid any strenuous physical activity on the night preceding testing.
In the morning participants will be asked to rest for 15 mins before 2 baseline blood samples (by finger prick) are taken. Participants will then be given one of the 3 test foods to consume within 10 mins and small blood samples will be taken at 15, 30, 45, 60, 90, 120, 150 and 180 min after consuming the food for measurement of blood glucose and insulin.
Blood sampling involves use of a finger prick device (as used by diabetics at home) which almost painlessly allows a small bead of blood to be massaged from the finger and used to monitor your blood glucose and insulin levels over the three hours after consuming the food.
During the three hours participants will be able to bring some paperwork to complete in the human clinic facility, and drink a set amount of water if thirsty, but consume no food until after the final blood test. At 0., 15, 60, 120 and 180 mins during the trial participants will be asked to fill out a short questionnaire to assess their hunger.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 73498 0
Dr John Monro
Address 73498 0
The New Zealand Institute for Plant and Food Research,
Private Bag 11600
Palmerston North
New Zealand
4442
Country 73498 0
New Zealand
Phone 73498 0
+6463556137
Fax 73498 0
Email 73498 0
John.monro@plantandfood.co.nz
Contact person for public queries
Name 73499 0
Dr Suman Mishra
Address 73499 0
The New Zealand Institute for Plant and Food Research,
Private Bag 11600
Palmerston North
New Zealand
4442
Country 73499 0
New Zealand
Phone 73499 0
+643556146
Fax 73499 0
Email 73499 0
Suman.mishra@plantandfood.co.nz
Contact person for scientific queries
Name 73500 0
Dr John Monro
Address 73500 0
The New Zealand Institute for Plant and Food Research,
Private Bag 11600
Palmerston North
New Zealand
4442
Country 73500 0
New Zealand
Phone 73500 0
+6463556137
Fax 73500 0
Email 73500 0
John.monro@plantandfood.co.nz