Are prevailing patterns of diet behavior in a population, assessed using factor or cluster analysis, related to risk of cardiovascular disease?
The goal of this systematic review project is to identify patterns of food and beverage intake that promote health and prevent disease. Historically, most dietary guidance has been based on research conducted on individual food components or nutrients. Dietary patterns are defined as the quantities, proportions, varieties, or combinations of different foods, drinks, and nutrients (when available) in diets, and the frequency with which they are habitually consumed. Factor and cluster analysis allow examination of the relationship between prevailing dietary patterns of a population and outcomes of public health concern. The objective of this systematic review was to assess the relationship between patterns of food and beverage intake, identified using factor and cluster analysis, and risk of cardiovascular disease (CVD).
Limited evidence from epidemiological studies indicates that dietary patterns, assessed using cluster or factor analysis, characterized by vegetables, fruits, whole grains, fish, and low-fat dairy products are associated with decreased risk of cardiovascular disease in adults. Evidence of a relationship between dietary patterns characterized by red and processed meat, sugar-sweetened foods and drinks, and fried foods and an increased risk of cardiovascular disease is limited and less consistent. (Grade: III-Limited).
Literature searches were conducted using PubMed, Embase, Navigator (BIOSIS, CAB Abstracts, and Food Science and Technology Abstracts), and Cochrane databases to identify studies that evaluated the association between dietary patterns defined using factor or cluster analysis and CVD risk. Studies that met the following criteria were included in the review: Human subjects; Ages: 2 years and older; Populations: Healthy and those with elevated chronic disease risk; subjects from countries with high or very high human development (based on the 2011 Human Development Index); randomized controlled trials, non-randomized controlled trials, or quasi-experimental studies; Sample size: Minimum of 30 subjects per study arm; Dropout rate less than 20 percent; Study assesses dietary intake using factor and cluster analysis; study considered cardiovascular disease and risks of cardiovascular disease; published in English in a peer-reviewed journal. The date range for the conduct of studies was unlimited.
The results of each included study were summarized on evidence worksheets (including a study quality rating) and evidence table. A group of subject matter experts were involved in a qualitative synthesis of the body of evidence, development of a conclusion statement, and assessment of the strength of the evidence (grade), using pre-established criteria including evaluation of the quality, quantity, consistency, magnitude of effect, and generalizability of available evidence.
- Twenty-two prospective cohort studies conducted between 1989 and 2012 (from 18 cohorts) were included in this review. To derive dietary patterns, 15 studies used factor analysis and 5 studies used cluster analysis. Two studies generated dietary patterns using both factor and cluster analysis. Study duration ranged from 2 to 21 years. Seven studies were conducted in the United States; two studies each were conducted in Sweden, Italy, Japan, and Denmark; and the remaining studies were conducted in the United Kingdom, Spain, Australia, Finland, Greece, Germany, and the Netherlands.
- Variability in the studies included in this review, including populations considered, dietary assessment methods used, the number and type of food groupings included in the analyses, and the statistical techniques employed, made comparisons among studies challenging.
- In general, the favorable patterns were variously labeled “Mediterranean,” “vegetable,” “prudent,” “whole grains and fruit,” “cereals,” “fish and olive oil,” and “Japanese.” The unfavorable patterns, were labeled as “Western,” “fats and processed meat,” “meat,” “animal food,” or “sweets” patterns.
- Nine studies examined dietary patterns and their association with CVD outcomes. Eight studies used factor analysis, and two used cluster analysis; only one study analyzed dietary intake beyond the baseline measure. Generally, dietary patterns characterized by vegetables, fruits, whole grains, fish, and low-fat dairy products were more consistently associated with a decreased risk of CVD, while patterns characterized by red and processed meat, sugar-sweetened foods and drinks, and fried foods were somewhat less consistently associated with increased risk.
- The evidence that evaluates the association between other related outcomes, as coronary heart disease, myocardial infarction, stroke, lipid levels, and blood pressure were insufficient and not consistent.
The ability to draw strong conclusions was limited by the following issues:
- In factor and cluster analysis, the consolidation of food items into food groups, the number of factors or clusters to extract, and even the labeling of components are subjective. Furthermore, patterns derived from either factor or cluster analysis may not be reproducible across studies because elements of dietary patterns and analytic decisions differ.
- Dietary pattern analysis using factor or cluster methods may not be very informative in determining which elements of the diet or which biological relationships between these elements are responsible for the health outcome.
- Some studies completed over long periods of time did not account for changes to subjects’ diets or seasonal variations in food supplies, which may have influenced the food components of patterns.
- The patterns derived through analyses may not represent the most beneficial or detrimental patterns relative to the health outcome of interest.