The Relationship Between Dietary Patterns and Carotid Intima Media Thickness, as an Early Biomarker of Cardiovascular Disease: A Systematic Review and Narrative Synthesis

Abstract

ObjectiveTo systematically review current literature on the association between empirically derived dietary patterns and carotid‐intima media thickness, an early marker of cardiovascular disease.BackgroundDietary pattern analysis has emerged as a complementary approach to single‐nutrient analysis for examining the relationship between diet and the risk of chronic diseases like cardiovascular disease (CVD). Carotid intima‐media thickness (CIMT) has been established as a robust early marker of CVD on the atherosclerotic pathway. Although a wealth of literature links dietary factors and traditional CVD markers, a limited number have investigated the relationship between dietary patterns, derived using empirical data, and CIMT, a novel CVD marker. This is a unique systematic review and narrative synthesis which investigates the association between dietary patterns and CIMT.MethodsA systematic search of MEDLINE, CINAHL and Web of Science (2000 to 2015) supplemented by manual searches of bibliographies was conducted. Studies that derived dietary patterns using a posteriori methods (principal component analysis (PCA)/factor analysis (FA)), a priori methods (investigator‐defined) or a combination (reduced rank regression (RRR)) were included with CIMT as the outcome. Most papers studied healthy adults (≥18 years) except two. The Critical Appraisal Skills Programme (CASP) checklist was adapted to assess each study for validity, methodology, and relevance. The narrative synthesis discusses the findings from each study according to the method used to derive the dietary patterns.ResultsOut of a total of 1582 papers, 15 papers were eligible for review. Six papers used empirical methods (PCA n=4, FA n=1, RRR n=1), while 9 papers used investigator‐defined methods to determine dietary patterns (refer to the figure). In general, of the papers using empirical methods, four reported a statistically significant association with increased CIMT. Overall, the dietary patterns identified in those studies were characterized by high consumption in ‘unhealthful’ food groups such as processed and red meat, soda and meal replacement drinks, refined grain and starchy foods. While two studies that identified dietary patterns empirically were associated with a decrease in CIMT, characterized by high consumption of ‘healthful’ foods namely fruits and vegetables, fish, and rice and low in the ‘unhealthful’ foods. Of the papers using investigator‐defined methods, four cross sectional studies showed that adherence to lacto‐vegetarian/low‐calorie vegan diets is associated with a decrease in CIMT. Dietary patterns derived from each study varied depending on derivation method and study design. When assessed for quality, RCTs scored the lowest, and cross sectional studies failed to provide sufficient information on the measurement of exposure variables. Cohort studies proved to be the most robust study design when assessed using the CASP criteria.ConclusionsFindings from this review are generally supportive of an association between greater adherence to dietary patterns characterised by higher consumption of ‘healthful’ foods and lower consumption of ‘unhealthful’ foods, and decreased CIMT. However, the evidence is heterogeneous as seen from the differences in CIMT measures with varying dietary patterns. Large‐scale prospective observational and interventional studies are needed to evaluate the association between dietary patterns and CIMT.Support or Funding Informationnone