A randomised controlled intervention trial evaluating the efficacy of an Australianised Mediterranean diet compared to the habitual Australian diet on cognitive function, psychological wellbeing and cardiovascular health in healthy older adults (MedLey study): protocol paper

Abstract

Background: The Mediterranean diet (MedDiet) is associated with considerable health benefits for cardiovascular and cognitive health, particularly within the Mediterranean basin. Whether Australian populations will similarly benefit from the MedDiet is unknown. We aim to assess the effects of a MedDiet on cognitive and cardiovascular health indicators amongst the elderly (MedLey study). Here we describe in detail the protocol for the MedLey study. Methods: Medley is a randomised, parallel controlled dietary intervention trial. Data collection occurred at the Sansom Institute for Health Research, University of South Australia, Adelaide, South Australia, Australia between 2013 and 2015. Omnivorous men and women aged ≥65 years, who were non-smokers, had no previously diagnosed cardiovascular disease, history of brain trauma, cognitive impairment, major disease or cancer were recruited from the general public (n = 166). The intervention comprised an Australianised version of the traditional MedDiet characterised by small amounts of red meat, processed deli meats and high sugar foods; moderate amounts of dairy and poultry; and a high plant food content including abundant extra virgin olive oil. Volunteers were stratified by age, gender and body mass index (kg/m 2 ) to follow either their habitual diet (control condition) or the intervention MedDiet for 24 weeks. Primary outcome measures included cognitive function, endothelial function, cerebrovascular flow, blood lipids, inflammatory markers, fasting glucose and insulin, blood pressure, and body composition. Secondary outcomes included food cravings, psychological wellbeing and DNA damage markers. These were assessed at baseline, 12 and 24 weeks. Dietary intakes were assessed at baseline, two and four months to assess adherence to the prescribed diet. For main outcome measures, groups will be compared over time using a linear mixed effects model, with Cohen's d effect sizes. Subgroup analysis based on adherence to the intervention, medications and alcohol consumption may be performed in an exploratory fashion.

A Mediterranean diet lowers blood pressure and improves endothelial function: results from the MedLey randomized intervention trial ,

“…The study protocol of the dietary intervention for cognitive and cardiometabolic health in a healthy elderly population (www.anzctr.org.au; ACTRN12613000602729) has been described elsewhere (22,23). Briefly, the study was a randomized, controlled, intervention trial with 2 parallel groups.…”

“…In secondary analyses, we further analyzed each time point (morning, afternoon, and evening) separately. Previously, we used independent t tests (continuous variables) and chi-square tests (categorical variables) to compare baseline characteristics of subjects who had baseline FMD scans with those who did not (22). There was no relation for age, diet group, sex, BMI, waist-to-hip ratio, or HDL cholesterol; only total cholesterol and LDL cholesterol were highest in subjects without scans.…”

“…For subjects in the MedDiet group, resources were provided that included a recipe book, guidelines for eating out, serving sizes, and the recommended number of servings. Participants also received foods (olive oil, nuts, legumes, tuna, and Greek yogurt) to increase the likelihood of adherence (22). Subjects in the HabDiet group received verbal instructions and a voucher to buy regularly consumed foods from supermarkets.…”

“…For the analysis of FMD, the right-side brachial artery was assessed with the use of a Logiq 5 Expert ultrasound machine (General Electric Corp.) (22). Participants were rested in a supine position $10 min before commencement in a temperaturecontrolled clinic room (228C).…”

“…At each of these time points, 3 consecutive measures of BP and heart rate were recorded with each reading spaced 1 min apart. The second and third measures were used in the analysis (22).…”