Digestive health effects of high amylose wheat in healthy Australian men and women

STUDY DESIGN The study will be designed as a completely randomised, double-blinded (where possible), controlled parallel intervention. During a 2-week low dietary fibre (<20g/day) run-in period, all participants will consume 160 g/day of the Control wheat- refined bread (Low Amylose Wheat). Participants will then be randomised to one of four groups (n=20 in each group). Each group will consume their assigned test grain products daily for a 4-week period. The intervention test foods will be bread and biscuits containing the following type of wheat flour: High amylose wheat – refined High amylose wheat – wholemeal STUDY DIET & TEST FOODS Other than the dietary changes outlined in this study protocol, participants will maintain their habitual diets for the duration of the 6-week study (fibre intake (not including test foods) limited to <20 g/day with energy intake to remain unchanged). During the 4-week intervention period the Control refined wheat group will continue to have a fibre intake <20 g/day and fibre intakes will increase above this level for the other intervention groups. The participants will also be instructed not to consume probiotics (including probiotic yoghurts and other foods containing probiotics such as Kombucha tea and Kefir) and refrain from using fibre supplements and laxatives. Each participant will be reviewed throughout the study by a Research Dietitian to ensure these changes are achieved and maintained. The intervention test foods will be bread and biscuits containing the following type of wheat flour: 1. High amylose wheat – refined 2. High amylose wheat – wholemeal 3. Control wheat – refined 4. Control wheat - wholemeal Participants will be required to consume 160g of their allocated test bread and 100g of test biscuits each day. Dietitian guidance will be provided to ensure that the test foods are consumed throughout the day and are incorporated into the participant’s usual diet. Prior to the low fibre run in participants will attend the Nutrition & Health Research Clinic and meet with a dietitian (week 0). Dietary intake will be assessed by a general diet history. This information will be used by the dietitian to help counsel the participant about consuming the low fibre diet (<20g/day). Anthropometric data will be collected by a trained Clinical Research Technician. Two 24 hour diet recalls will be conducted over the phone on consecutive days at the end of the low fibre run-in period and at the end of the 4 week test grain period (weeks 2 and 6). These diet recalls will coincide with the 48 hr faecal collection. Daily energy, macronutrient and micronutrient intake data will be calculated using FoodWorks Professional 9 software (Xyris Software, Highgate Hill, QLD, Australia). Dietary and study compliance will be assessed via an online survey, weekly. Survey results will be assessed by trained Clinical Research Technicians and/or Research Dietitians and contact will be made with participants if protocol deviations occur. A gut comfort questionnaire will also be completed at weeks 2, 4 and 6. 24-hour diet recall (Computer Assisted Telephone Interview) Four computer-assisted telephone interview (CATI) 24-hour diet recall questionnaires will be completed with a research dietitian. These will be conducted over the phone at the end of the low fibre run in period (week 2) and at the end of the 4 week intervention period (week 6). These diet recalls will coincide with the 48 hour faecal collection periods. The 24 hour diet recalls require the participant to recall their food, drink and supplement intake for the previous 24 hours. The three pass methodology will be used to prompt participants to recall their intake in as much detail as possible, and reduce error by providing opportunity to remember forgotten foods. The research dietitian will enter the outcomes of the interviews directly into Foodworks at CSIRO. Digestive Comfort questionnaire Digestive comfort will be assessed by a validated short questionnaire which has been used in previous successful bowel health studies performed by CSIRO. It will provide semi-quantitative data and other information on bowel habits, such as defecation frequency and stool form and also abdominal disturbances (bloating, wind etc) that sometimes accompany a shift to a diet high in fibre. Product Consumption & Accidental Intake checklist A short checklist will be completed by participants each day to aid their adherence to the study dietary protocol and enable us to determine whether a participant has fully complied with the study design. It will also provide information that will assist with statistical analyses and interpretation of the results.