Comparison of the Dietary Antioxidant Profiles of 21 a priori Defined Mediterranean Diet Indexes

Background The Mediterranean Diet (MD) is a dietary pattern that features a high quotient of antioxidant-rich foods. Differences in the level of dietary antioxidants intake reflected by different MD indexes has received little research attention. Objective The purpose of this study was to compare the dietary antioxidant profile of 21 a priori defined indexes of adherence to the MD. Design A cross-sectional study. Participants/setting A total of 14,756 participants belonging to two Spanish European Prospective Investigation into Cancer and Nutrition cohorts, aged 32 to 69 years, recruited between 1992 and 1996, were included. Main outcome measure Participants provided information on diet through a validated diet history questionnaire. Antioxidants (vitamin C, beta carotene and alpha-tocopherol), total antioxidant capacity, total polyphenols, flavonoids, and polyphenol antioxidant content score were estimated using different food composition databases. Twenty-one MD indexes were operationalized. Statistical analysis Spearman correlation coefficients between the indexes were calculated and hierarchical clustering was applied to identify cluster groups. Weighted kappa statistic was estimated to value the scoring agreements between indexes. Antioxidant profiles between the MD indexes were compared based on geometric mean intakes. The relationship between each MD index with the components of the antioxidant profile was evaluated using linear multivariable regression analysis. Results Correlation patterns between the MD indexes showed that about half of the indexes were moderately-to-weakly correlated with each other (rho<0.5). The main cluster groups derived denoted the high-, moderate-, and low-correlated MD indexes. Three MD indexes (MD pattern-2002, Prevention with MD, and Alternate MD index) presented the highest mean intakes of antioxidant vitamins, total antioxidant capacity, total polyphenols, flavonoids, and polyphenol antioxidant content score. These and other indexes (mainly those belonging to the MD Scale group) captured higher intake levels of dietary antioxidants overall. Conclusions The level of dietary antioxidant intake that is captured through the different MD indexes differed due to the variation in their construction. Study results also suggest that some MD indexes reflect a higher antioxidant profile.