None listed
Conditions
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.
Interventions
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 t
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.
Sponsors
The New Zealand Institute for Plant and Food Research
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Prevention
Masking
Open (masking not used)
Eligibility
Sex/Gender
All
Age
18 Years to 65 Years
Healthy volunteers
Yes
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.
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.
Outcome results
None listed