Benefits and Harms of the Mediterranean Diet Compared to Other Diets

s from MEDLINE (n = 7,672) were reviewed in duplicate independently by investigators and research associates. Abstracts from the CINAHL database (n = 131) and Cochrane Library (n = 1,799) were reviewed by a co-investigator or research associate. Trained researchers identified articles published in peer-reviewed journals related to one of the Key Questions (KQs). For studies addressing KQs 1 and 2 in diseases other than cancer, RA, or cognitive impairment we included RCTs or controlled clinical trials (CCTs) with at least 100 subjects followed for at least one year. For studies of RA and cognitive impairment we included RCTs, CCTs, and cohort studies with any number of participants and no limit on follow-up time. For studies of cancer and for KQ3 we included RCTs and cohort studies with at least 100 participants followed for at least one year. In addition, in order to be included, studies addressing Benefits and Harms of the Mediterranean Diet Evidence-based Synthesis Program Compared to Other Diets 16 KQ3 must have taken place in the United States or Canada. For all questions and outcomes, we excluded case series, case reports, qualitative reports, narrative reviews, editorials, or letters. Studies must have also reported one of our outcomes of interest as defined in the Analytic Framework (Figure 1) and PICOTS (above). All included studies met our definition of a Mediterranean diet. In the randomized trials, the composition of the intervention diets were defined a priori. In the cohort studies, food frequency surveys (either self-administered or administered by research staff) were typically used to categorize subjects’ diets based on validated dietary indices. Commonly used indices include the Mediterranean-diet score, the alternate Mediterranean-diet score (aMED), the Healthy Eating Index (HEI), and the Alternate Healthy Eating Index (aHEI). For these indices we generally compared the highest quantile of conformity to a Mediterranean diet to the lowest. We excluded the following: ∑ Studies that did not involve outpatient adults; ∑ Studies with diets that were not labelled Mediterranean and did not test or measure a diet that met our criteria for a Mediterranean diet (stated above); ∑ Studies in women who were pregnant or lactating; and ∑ For KQ3, studies that were conducted in countries other than the US and Canada. Full-text reports of studies identified as potentially eligible were obtained for further review using the inclusion and exclusion criteria described above. Each article was independently reviewed by 2 trained researchers. Reasons for excluding a study at full-text review were noted.