Review and special articlePsychosocial Predictors of Fruit and Vegetable Consumption in Adults: A Review of the Literature
Introduction
Higher consumption of fruits and vegetables has been found to be potentially protective against a number of chronic diseases such as type 2 diabetes, cardiovascular disease, obesity, and various cancers.1, 2, 3, 4, 5, 6, 7, 8 However, fewer than one quarter of Americans eat the recommended five or more daily servings of fruits and vegetables.9, 10, 11 Because Americans are still falling short of the recommendations, continued efforts are needed to address this issue. While programs such as “5-A-Day” and “Fruits and Veggies—More Matters” address this problem on a macro level, behavioral interventions are still viable for increasing fruit and vegetable intake (FVI).12
Understanding determinants of behavior is a key component of developing effective behavioral interventions.13, 14, 15 Behavioral interventions induce change in behavior by operating at least partially through their impact on psychosocial variables,16 but most causal models of FVI account for less than 30% of the variance in dietary behaviors.16, 17 The limited ability of existing theoretical models of behavior to predict FVI highlights the need to evaluate the efficacy of specific models and their concomitant variables as potential determinants of FVI.16
Literature reviews have been conducted on the health benefits of FVI,2, 3 the efficacy of dietary interventions,18, 19, 20, 21 and dietary outcome measures,22 but a review of psychosocial determinants of FVI is lacking, particularly one that addresses the findings from more recent mediation analyses of FVI interventions. Mediation analysis allows for more sophisticated theory testing through a focus on potential mediators of behavior change.13, 23 This paper provides a review of individual psychosocial determinants of adult FVI, examining both cross-sectional and prospective studies. Prospective studies included both those that employed mediation analyses and those that did not. Studies were assessed on quality of execution and design suitability, factors that were compared across studies to examine the strength of evidence for each psychosocial construct.
Section snippets
Search Strategy
The following sources were surveyed to identify potential papers: bibliographic databases (e.g., PubMed, PsycINFO), references cited in collected articles, conference abstracts, and unpublished work through personal communication with researchers. Articles were retrieved using a combination of the following keywords: fruit and vegetable intake/consumption, mediating variables, mediators, mediation, psychosocial determinants/factors/predictors/variables, diet/dietary intake, nutrition, and
Results
A total of 1128 articles were identified, of which 35 were eligible for review after exclusionary criteria were applied. Twenty-one studies were cross-sectional or descriptive in design, including papers that presented only baseline results of a longitudinal study. Fourteen studies were prospective, six of which tested for mediation. The Table 1 matrix of psychosocial variables highlights the direction of association between predictors and FVI across all studies.
Discussion
The reviewed studies exhibited diversity in research design, measures, and analytic methods, employing psychosocial variables from a number of theories such as SCT, HBM, TPB, TTM, and SDT. Each study and construct was assessed for direction of significant effects, quality of execution, design suitability, and frequency, and summarized with an evidence-of-effectiveness rating for each construct in Table 2 (with detailed ratings in Appendix A6). Based on the Guide's methodology, strong or
Limitations
Despite the use of a stringent review protocol for assessing each article, there were some limitations to this study. First, significant variation was observed in the outcome measure of FVI, with most studies employing shorter or brief measures of FVI and only a few using more complete measures of diet such as 24-hour recall (24HR). A recent review of fruit and vegetable screener methods noted that measures with greater numbers of items and those that assessed portion size had greater validity
Conclusion
The primary goal of this literature review was to assess and report on the most promising psychosocial determinants of adult FVI. There are many strengths to this review, including the variety of studies, comprehensiveness of scope, and use of the Guide's methodology for systematic review, which enables evidence-based recommendations. In addition, by addressing a key gap in the literature, the findings are intended to provide timely information for both theoreticians and interventionists.
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