None listed
Conditions
Brief summary
There is almost universal acceptance that appropriate nutrition is a pivotal component of attempts to reduce the burden of disease such as obesity, diabetes, cardiovascular disease and some cancers. Healthy eating also has the potential to help achieve equity of health outcomes amongst population groups where inequalities exist such as Maori and Pacific people in New Zealand. While some dietary advice is generally accepted, there is continuing debate regarding the amount and type of dietary carbohydrate. The project proposed is to better understand the potential health benefits of wholegrain foods. There is convincing evidence that wholegrain consumption protects against colorectal cancer, type 2 diabetes (T2) and cardiovascular disease. Given the global escalation of rates T2 and the importance of colorectal cancer and CVD it is hardly surprising that substantial increases in whole grains have been recommended worldwide. However, what it is in whole grains or the parameters of their consumption that confer health benefits has not been clearly identified. Whole grains products are recommended in New Zealand and abroad in dietary guidelines however current definitions make no mention of structure and particle size, referring only to grain constituents. Given that an increasing number of relatively refined wholegrain products (as presently defined) are now appearing on supermarket shelves, the potential effect of reducing wholegrain particle size must be considered. It seems possible, indeed likely, that so-called wholegrain foods consumed today may be very different from those available several decades ago in the prospective studies where the benefit of whole grains were clearly demonstrated. The most recent evidence of the importance of wholegrain particle size on metabolic markers comes from a study by Jarvi et al (1999). Their objective was to compare the effects of diets high in carbohydrate foods that were either minimal processed or highly refined in people with T2. Macronutrient composition and type and amount of dietary fibre were identical. After 24 days, measures of glucose and insulin were 30% lower after the diet of more intact whole grains. LDL cholesterol was also lower. No further research on this topic has been published since, despite it being urgently required. The immediate objectives of the proposed research are: (1) to develop a range of wholegrain products with various particle sizes produced under a range of typical food processing conditions and test their acceptability; (2) to examine the acute physiological effects after ingestion of wholegrain test products in healthy subjects and those diagnosed with T2. This research will determine the effects of processing these wholegrain products and to inform, if indicated, a change in the definition. This research has the potential to enhance nutrition guidelines in terms of reducing the risk of non-communicable diseases in New Zealand and internationally.
Interventions
This study is a crossover design to measure the postprandial blood glucose response to wholegrain foods of different fibre particle size. Each food exposure is an intervention of the study. Each wholegrain product is made primarily from wheat, but differs in its degree of food processing and therefore fibre structure particle size. Each wholegrain product will be defined by its fibre particle size, and the glycaemic response it generates when compared to a recognised glucose standard.
The categ
This study is a crossover design to measure the postprandial blood glucose response to wholegrain foods of different fibre particle size. Each food exposure is an intervention of the study. Each wholegrain product is made primarily from wheat, but differs in its degree of food processing and therefore fibre structure particle size. Each wholegrain product will be defined by its fibre particle size, and the glycaemic response it generates when compared to a recognised glucose standard. The categories of food being tested are: Bread comparison * A bread with refined grain components in the same ratio found in whole grains * A bread made with finely milled whole grains * A bread made with a mixture of finely milled and partially ground whole grains (i.e. kibbled) * A bread made with a mixture of finely ground, partially ground and whole grains Cracker Comparison * A cracker made with finely milled whole grains * A cracker made with a mixture of finely ground, partially ground and whole grains Cereal Comparison * A cold cereal made with finely milled whole grains * A cold cereal made with whole grains * A hot cereal made with finely milled whole grains * A hot cereal made with whole grains The postprandial blood glucose response to these foods and relevant controls will be measured inline with accredited Glycaemic Index (GI) testing protocols. This requires study participants to attend a testing facility in person. Each morning of the test participants will arrive at the testing facility having consumed no food since 10pm the night before. Baseline capillary blood glucose will be measured in duplicate. Wholegrain products containing 50 grams of available carbohydrate will be consumed, 250ml of water will be provided with each food. The participant's postprandial blood glucose response will be identified by a series of capillary blood glucose measures. In participants of normal glucose tolerance (NGT), these measures are taken at 15, 30, 45, 60, 90, and 120 minutes after meal commencement. For participants diagnosed with type 2 diabetes (T2), these measures are taken at 15, 30, 45, 60, 90, 120, 150, and 180 minutes, so to record their prolonged blood glucose response. This is a standardised process with all participants tested in the same manner for each exposure. In addition to the 10 wholegrain products being tested, each participant will attend three mornings of a control containing an equivalent amount of carbohydrate. Each test morning will require participants to be present for 2.5 (NGT) to 3.5 (T2) hours. There will be no more than three test mornings per participant per week resulting in a minimum 24 hour washout before the next intervention. With 13 morning exposures in total (10 foods, 3 controls) participant will be enrolled in the study for a minimum five weeks. Researchers of this study have published widely in this area. Data from each exposure will be measured by researchers and assistants trained to do so inline with the University of Otago's internationally accredited GI testing facility. Intervention order will randomised by product for the breads, crackers, and two controls (eight mornings). We will then give participants the opportunity to continue testing the cereals and final control (five mornings) in randomised order. If participants choose not to continue and test the cereals we will recruit new participants so that 20 normal glucose participants and 20 participants with type 2 diabetes have tested all wholegrain products. Adherence will be recorded and fidelity with the required preparations: no food from 10pm the night before, a good source of carbohydrate consumed with the evening meal, alcohol restricted and physical activity in the 24 hours standardised before each test morning. Any participants who decides not to complete the study can do so at no disadvantage. However, we will ask them to fill in a short form to determine the reason for not completing the study. If the participant prefers not to fill in such a form they can do so at no disadvantage. To reduce the non-completion rate, a screening visit will occur before any postprandial response is measured. The screening visit is a chance for interested applicants to meet the researchers collecting the data in person, confirm their eligibility, and to be briefed on the expectations of study participation. Should informed consent be provided, participants will then be asked a series of baseline questions and undergo measurements (height, body weight, waist circumferences, glycated haemoglobin and lipid profile). During this study additional measures will be made during the postprandial blood glucose response. These measures do not involve additional blood samples or invasive measures. They are described clearly as secondary outcomes of this study.
Sponsors
University of Otago
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Prevention
Masking
Blinded (masking used) (Subject, Investigator)
Eligibility
Sex/Gender
All
Age
18 Years to 75 Years
Healthy volunteers
Yes
Inclusion criteria
Participants will be from two separate groups of the population. One group is of participants diagnosed with type 2 diabetes mellitus aged 18 to 75-years recruited through general practices, hospital outpatient clinics, the local diabetes society and services that cater for people with chronic diseases. The second group will be of 18- 75 year olds without diagnosed type 2 diabetes or any evidence of impaired glucose tolerance. Presence of comorbidities will not exclude participation.
Exclusion criteria
For all participants pregnancy, lactation, inability or unwillingness to comply with the intervention requirements will exclude participation.
Outcome results
None listed