The MEDENI Trial: A microbiome-targeted Mediterranean diet intervention in residential aged care to reduce frailty.

The study is a parallel crossover randomised controlled dietary trial conducted in a residential aged care setting. The intervention will be the consumption/exposure to a Mediterranean diet (MedDiet). The aim of this study it to determine the effect of a MedDiet on intestinal microbiology, frailty, wellbeing and cardiovascular and cognitive health. The MedDiet is a prescribed diet containing 15-45 mL extra-virgin olive oil/d, abundant vegetables, fruit, nuts, legumes, and whole grains, as well as moderate fish, poultry, and dairy foods. MedDiet will replace standard breakfast and dinner, whilst the usual diet will remain for lunches. The trial will include two arms: Arm 1 (treatment): The MedDiet will be prescribed for a 4-week duration, followed by a 4-week washout, and then the control diet will be prescribed for 4 weeks. Arm 2 (control): The control treatment - Habitual diet (HabDiet) - will be provided for a 4-week duration, followed by a 4-week washout, and then the MedDiet will be prescribed for 4 weeks. The control treatment is the residents’ habitual diet. The menu (breakfast, lunch, dinner) is prepared and provided by the residential aged care facility (RACF). For each arm, the diets will be prepared and provided by the residential aged care facility staff. Delivery of the diets will be face-to-face by the facility staff who are known to the residents. The trial will take place within the aged care facility, and preparation of the diet will occur in-house within the facility kitchen. The intervention will not be personalised, as individuals with clinically-indicated requirements relating to dietary composition (e.g. kidney disease, diabetes, food allergies) or preparation (e.g. severe dysphagia, gastric feeding), will be excluded from the trial, as will those receiving palliative care, and those who have a colostomy or ileostomy, or severe gastrointestinal disease. However, the MedDiet may be adapted for the aged care study population to ensure sufficient variation and participation choice. Adherence to all diets will be monitored using menu checklists, including percentage of meal consumed, number of eating occasions in a day, and number of days participated.