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

INTERVENTION: 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 CONDITION: Diet and Nutrition ‐ Other diet and nutrition disorders Frailty;Aged care; ; Frailty ; Aged care Oral and Gastrointestinal ‐ Other diseases of the mouth, teeth, oesophagus, digestive system including liver and colon PRIMARY OUTCOME: Relative (within‐subject) change in faecal microbiota composition through comparison of pre‐ to post‐intervention weighted UniFrac distance. ; ; Specifically, change in the relative abundance of 44 discrete bacterial taxa known to be predictive of response to MedDiet in senior populations. The major taxa include Faecalibacterium prausnitzii, Roseburia (R. hominis), Eubacterium (E. rectale, E. eligens, E. xylanophilum), Bacteroides thetaiotaomicron, Prevotella copri and Anaerostipes hadrus, Ruminococcus torques, Collinsella aerofaciens, Coprococcus comes, Dorea formicigenerans, Clostridium ramosum, Veillonella dispar, Flavonifractor plautii and Actinomyces lingnae.; Microbiota composition will be defined using 16S rRNA gene amplicon analysis in an established analytical pipeline. [Stool samples will be collected at day 0 (baseline), 28, 56, and 84 (from trial commencement). Day 84 (at the conclusion of the second diet) will be the primary outcome endpoint.] ; INCLUSION CRITERIA: 1. Long‐term residents (greater than 6 months) of an aged care facility. 2. Informed consent. SECONDARY OUTCOME: Change in blood pressure.[Blood pressure will be measured at day 0 (baseline), 28, 56, and 84 (from trial commencement) using a blood pressure monitor (sphygomomanometer).] Change in depression symptoms.[Depression in participants will be measured using the Geriatric Depression Scale (GDS) at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Change in frailty status.[Frailty will be determined using the FRAIL Scale at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Change in malnutrition status.[Extent of malnutrition will be determined using the Malnutrition Assessment (MNA) at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Change in mood.[Mood will be evaluated using the Bond‐Lader Visual Analogue Mood Rating Scale (BL‐VAS) at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Change in overall gastrointestinal health.[Gastrointestinal health will be measured using the Gastrointestinal Health Questionnaire (GHQ) at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Change in quality of life.[Quality of life will be determined using the Assessment of Quality of Life (AQoL‐8D) at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Change in quality of social relationships.[Social networking quality will be assessed using the Social Network Index (SNI) at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Change in serum inflammatory markers, including high‐sensitivity C‐reactive protein, tumor necrosis factor alpha, interleukin 1b, and interleukin 6, as assessed by enzyme‐linked immunosorbent assay (ELISA) of blood samples[Blood samples will be collected at day 0 (baseline), 28, 56, and 84 (from trial commencement) via venepuncture following overnight fasting. ] Change in serum markers as assessed by blood sample. ; Examples of markers screened include LDL, and HDL cholesterol, triglycerides, glucose, and insulin.[Blood samples will be collected at day 0 (baseline), 28, 56, and 84 (from trial commencement) via venepuncture following overnight fasting. ] Change in short‐term memory and cognition.[Memory and cognition will be measured using the Corsi Block Tap Test at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Change in short‐term mood.[Mood will be profiled using the Profile of Mood States (POMS) at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Change in sleep quality.[Sleep quality will be assessed using the Sleep Quality Index (SQI) at day 0 (baseline), 28, 56, and 84 (from trial commencement).] Changes in hip measurements[Hip circumference will be measured at day 0 (baseline), 28, 56, and 84 (from trial commencement) with a tape measure. ] Changes in stool characteristics.[Stool characteristics will be assessed using the Bristol Stool Score in conjunction with the stool sample collection at day 0 (baseline), 28, 56, and 84 (from trial commencement). ] Changes in waist measurements[Waist circumference will be measured at day 0 (baseline), 28, 56, and 84 (from trial commencement) with a tape measure. ] Changes in weight measurements.[Weights will be measured at day 0 (baseline), 28, 56, and 84 (from trial commencement) with digital scales. ]