Bioactive Dietary Pattern for Blood Pressure (BioBP) for People with Type 2 Diabetes and Pre-diabetes; A Randomised Pilot Cross-Over Feeding Study

Eight-week dietary intervention consisting of a 2-week run-in period (habitual/usual diet) followed by dietary pattern 1 for 2 weeks, 2-week washout period (habitual/usual diet), then lastly dietary pattern 2 for 2 weeks in a randomised order. The entirety of the diet (i.e., 3 main meals and snacks per day) will be provided to participants during dietary phase 1 and 2. Participants will supply their own meals and foods during the run-in and washout periods. Participants will be instructed to return to and maintain their habitual diet in the run-in and washout period, with adherence to this assessed with 2x 24 hour recalls at each timepoint including washout and run-in periods. The two dietary phases will consist of a “healthy Australian dietary pattern + bioactive foods” (HAD+) and a “healthy Australian dietary pattern” (HAD) that will be matched to participant’s usual caloric intake as assessed during the run-in period. Both the HAD+ and HAD will be matched for their sodium and potassium intakes to ensure this does not confound blood pressure (BP) responses. Energy, sodium and potassium for each diet was created using Foodworks. Dietary intake and compliance will be checked using 24 hour food recalls and spot urine samples. The HAD+ will have foods from the 5 core food groups from the current Australian Dietary Guidelines for adults with the addition of high bioactive foods that have been associated with reducing BP. The diet aims to meet the Acceptable Macronutrient Distribution Ranges (AMDR) e.g., 15-25% energy from protein, 45-65% energy from carbohydrates, 20-35% energy from fat; less than or equal to 10% energy from saturated fat and less than or equal to 1% energy from trans fat. Fibre intake may exceed the 25-30g/day recommendation due to the focus on soluble fibres. Sodium/potassium ratio will be matched with the HAD+ and the HAD plan. Nitrate rich vegetables are also included in this diet. The key foods in the HAD+ diet will include oats, beetroot, leafy green vegetables, flaxseeds, citrus fruit, and mixed nuts. All meals and snacks are provided to participants for the duration of both 2-week diet intervention phases. This includes pre-prepared main meals (e.g., ready made fresh meals or frozen meals), fresh produce, cereals and snacks. Study investigators calorie-match the foods (to the participants baseline usual calorie intake) to be provided which are placed as a grocery order by the study investigators during the appointment with the participants at the preceding phase. Participants collect the pre-ordered and pre-paid grocery items at their nearest allocated supermarket chain or via home delivery. The dietary intervention has been designed by and will be monitored by study coordinators who are also accredited practising dietitians. Participants are instructed to avoid consuming non-study foods, with usual beverage intake permitted except for discretionary choice beverages. Adherence to protocol will be examined during the 2-week run-in & washout periods prior to the feeding interventions and will be reassessed throughout the feeding intervention periods. Participants who do not meet adherence guidelines during the run-in period will be withdrawn from the study prior to randomisation. Adherence measures during the run-in period will include: • Collection of two 24-hour recalls • Record keeping of habitual consumption of tea, coffee, and alcohol (using Easy Diet Diary app or written food record as per participant preference) • Record keeping of any food consumed out of the home e.g., takeaway, restaurant / café foods (using Easy Diet Diary app or written food record) • Completion of one AES®-Heart survey • Collection of each biospecimen: urine, blood and faecal samples • Completion of one 24-hour ambulatory BP monitoring After completion of each dietary intervention phase, participants undergo a 2-week washout period where they return to their usual food habits, eating their own food (i.e., no food is supplied during the washout period). Upon enrolment, consent participants commence a 2-week run-in period prior to their first diet allocation. During the run-in period where they continue to consume their habitual diet (note, food is not supplied by study investigators for the run-in period). The run-in period includes collection of baseline data.