Effect of Nutritional INterventions on Autophagy (The NINA Study)

This study is a single-site, single blinded, randomised crossover trial that aims to measure the effect of a four week modification of dietary macronutrient intake on autophagic flux (i.e. a cell mechanism that cleanses the cells) in fasting healthy individuals. Participants will be randomised to one of two study diets for four weeks before crossing over to the other diet, with a four week washout period between diets. Both diets are healthy and balanced and are designed by a dietitian. Each diet has a different macronutrient profile. The reference diet has an ‘average’ macronutrient profile, whereas the intervention diet has an 'altered' macronutrient profile. Participants will be provided with individual 7-day rotating menus and will be asked to complete menu checklists daily to record any food prescribed that was not eaten and any food eaten that was not prescribed. The study design is comprised of an online screening survey (30 minutes), a screening visit (1 hour) followed by four, 1.5 hour metabolic visits (M1, M2, M3, M4). All participants will have similar visit schedules (minimum 28 days on diet) and measures of adherence. Eligible participants will attend the first metabolic visit (M1) where they will be randomised to one of the two study diets and will be asked to adhere to this diet for a four week (minimum 28 day) intervention period. After the first diet intervention, participants will attend the second metabolic visit (M2), following this visit they will commence the four week washout period where participants will be allowed to consume their regular diet. At the end of the washout period, participants will attend the third metabolic visit (M3) and be allocated to the diet that they were not allocated to during the first four weeks. After a further four weeks on the second diet intervention, participants will attend the fourth metabolic visit (M4) which is the end of the study. At each metabolic visit participants will arrive at the South Australian Health and Medical Research Institute in the morning after a 12 hour overnight fast. Body weight, height, waist circumference, hip circumference, hand grip strength, body composition, and blood pressure (following 10 minute seated rest) will be measured using standardised procedures. Following this fasting blood samples will be drawn. Participants will also complete a series of questionnaires to assess quality of life, sleep habits, eating behaviours, and physical activity. At the end of both dietary periods (visits M2 and M4), participants will be asked to complete a survey to record diet preference and satisfaction. POST COMPLETION: This project has ethical approval by the University of Adelaide HREC for limited disclosure to participants. Please find the information below that was approved to be disclosed once the last participant has completed their last appointment. This research involves limited disclosure in relation to the difference in protein amounts between the two study diets. To prevent study participants from trying to guess which diet is the ‘Average Protein Diet’ and which diet is the ‘Reduced Protein Diet’ and therefore avoid bias, the participant information sheet does not outline that the purpose of the study is to investigate the effect of dietary protein intake on autophagy (Attachment 2). The wording has been kept general and states that the study aims to measure the effect of diet composition on autophagy in humans. The project involves low risk participants only, therefore we anticipate that the limited disclosure will not affect participants adversely. After their participation has ended, participants will be provided with information about the aim of the research and an explanation of why the omission was necessary and offered the opportunity to withdraw any data or sample provided by them. There is no likely reason for thinking that participants would not have consented if they had been fully aware of what the research involved (National Statement Chapter 2.3). The identity of the two study diets used as interventions are as follows: Intervention (2 x 4 weeks = 8 weeks) This is a crossover study. Participants will be first be randomly assigned to one of the two diets from M1 to M2. From M3 to M4, they will be assigned to the study diet they have not been assigned to from M1 to M2. • Average Protein Diet: a control comparator diet that is similar to the ‘typical Australian diet’, will be delivered at calculated energy balance based on equations we have previously validated. This will be a nutritious whole foods diet with a macronutrient profile of 20 % protein, 30 % fat (<10 % saturated) and 50 % carbohydrate, with 30 g of fibre. This group will receive the same information and study visits as other group. • Reduced Protein Diet: This diet will be similar to the control diet, except macronutrients will be given at 10 % protein, 30 % fat (<10 % saturated fat), 60 % carbohydrate, ~30 g of fibre/day. This diet will provide 0.7g of protein per kg of body weight (the recommended minimum daily protein intake).