Nutritional biomarkers comparing a healthy versus a typical Australian diet: a Feeding Study in Australian Adults.

The Healthy Australian Diet (HAD) will provide foods to adequately meet the recommended servings of the 5 core food groups according to the current Australian Dietary Guidelines for adults e.g., 5.5 servings of grains/cereals; 5 servings of vegetables/legumes/beans; 2 servings of fruit; 3 servings of milk/yoghurt/cheese/alternatives and 2.5 servings of lean meats/alternatives. 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. Some emphasis will be given to specific nutrient targets such as fibre, free sugars, and sodium. Fruits and vegetables that are rich in beta-carotene (e.g., carrots, pumpkin, tomatoes, red capsicum, and sweet potato) will be emphasized during this dietary pattern. Characteristics of the food choices will reflect a high diet quality consistent with recommendations in the Australian Dietary Guidelines. 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 final appointment with the participants at the preceding phase. Participants collect the pre-ordered and pre-paid grocery items at their nearest allocated supermarket chain. 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 accept for discretionary choice beverages. Adherence to the dietary intervention will be assessed via the following tools: • Completion of Participant Protocol Adherence Check List • Three 24-hour food recalls per intervention phase as well as during run-in and washout to monitor dietary intake • Daily record keeping of consumption of tea, coffee, and alcohol (using Easy Diet Diary app) • Record keeping of any food consumed out of the home e.g., takeaway, restaurant / café foods and/or any non-study foods (using Easy Diet Diary app) • Completion of Australian Eating Survey surveys at the end of each diet phase • Attend two virtual study check-ins where investigators answer any questions to ensure participants adhere to protocol • Measurement plasma metabolites for respective indicator foods during each diet phase will be used as dietary biomarkers to objectively assess compliance to diet protocol 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: social, medial, physical and demographic; bio-sampling (blood, plasma, urine, faecal), anthropometry, usual dietary intake and determine study adherence (i.e., attending appointments and completing various data collection measurements as outlined in the participant information sheet they would have consented to).