Research Article
Understanding Adherence to 5 Servings of Fruits and Vegetables per Day: A Theory of Planned Behavior Perspective

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Abstract

Objective

The primary purpose of the present study was to examine the utility of the Theory of Planned Behavior (TPB) in explaining the 5-A-Day intentions and behavior of college students. A secondary purpose was to determine whether any of the TPB relationships were moderated by gender or ethnicity.

Design

A prospective design that asked college students to complete a baseline TPB 5-A-Day questionnaire and a fruit and vegetable consumption measure 1 week later.

Setting

Undergraduate fitness and health classes at 2 universities in the southern United States.

Participants

511 college students with a mean age of 19.8 years (standard deviation = 2.71).

Main Outcome Measures

TPB variables and fruit and vegetable consumption.

Analyses

Path analyses and invariance (ie, to examine ethnic and gender moderated) analyses.

Results

Affective attitude (β = .16, P < .05) and perceived behavioral control (β = .59, P < .05) were significant predictors of intention, which in turn was a significant predictor of behavior (β = .32, P < .05). Follow-up invariance analyses showed that none of the TPB relationships was moderated by gender or ethnicity.

Conclusions and Implications

The TPB may be a useful framework on which to base a 5-A-Day intervention for male and female college students of different ethnic backgrounds.

Introduction

The World Health Organization has identified low fruit and vegetable consumption as a significant risk factor for negative health consequences.1 Global estimates reveal that low fruit and vegetable consumption is responsible for 31% of ischemic heart disease, 11% of stroke, and 19% of gastrointestinal cancer. Moreover, the majority of Americans (approximately 77%) fail to consume the recommended 5 servings of fruits and vegetables per day (5-A-Day),2 with consumption being particularly low among college students (only 7% meet the 5-A-Day recommendation).3 Consequently, college students are in need of a 5-A-Day health promotion intervention.

Although the 5-A-Day guideline is widely accepted within the US and abroad, no studies have specifically examined the correlates of 5-A-Day in a college population, which may be a useful step in the development of a 5-A-Day behavioral intervention.4 Different theoretical approaches, such as the stages of change5, 6 and social cognitive theories,7, 8 have been employed to explain general fruit and vegetable consumption in noncollege samples; however, one theory that has received increased attention is the Theory of Planned Behavior (TPB).4 According to the TPB,9 a central predictor of behavior is an individual's intention to perform the behavior. Intention is said to be influenced by 3 factors: attitude, subjective norm, and perceived behavioral control. Attitude reflects a person's appraisal of the behavior to be performed. Subjective norm reflects the perceived social pressure to engage or not engage in a behavior. Perceived behavioral control reflects the perceived ease or difficulty of engaging in a behavior, which can be influenced by both past successes and foreseen barriers with the selected behavior.

To date, the limited research examining fruit and vegetable consumption within the TPB has consistently shown that attitudes, subjective norm, and perceived behavioral control are significant predictors of intention in youth10 and adults.11, 12, 13, 14, 15, 16 In terms of behavior, some studies have shown that either intention12, 13 or perceived behavioral control11, 14 was the sole predictor of fruit and vegetable consumption, whereas other studies10, 15, 16 found both to be significant predictors. At any rate, the aforementioned studies provide preliminary support for the TPB in explaining fruit and vegetable intake intentions and behavior in noncollege samples.

In addition to the clarification issue surrounding the interrelationships among intention, perceived behavioral control, and fruit and vegetable consumption, there are other limitations that need consideration. First, to date no studies in a college sample have been published. Given the importance placed on context within the TPB,9 it would be premature to make generalizations from existing TPB research in other contexts to the college population. Second, there is international acceptance for the 5-A-Day guideline, yet only 1 fruit and vegetable study in a noncollege sample15 actually used the term “5-A-Day” in the item stems to measure the TPB constructs specific to this behavior. Consequently, developing a potential 5-A-Day campaign for college students based on the general fruit and vegetable consumption literature may not be optimal. Third, previous TPB research pertaining to fruit and vegetable consumption used a singular attitude scale. However, it may be more informative to differentiate affective (eg, eating 5 servings of fruits and vegetables per day is enjoyable) and instrumental (eg, eating 5 servings of fruits and vegetables per day is beneficial) attitudes, as they have been shown to have differential relationships with intention in the physical activity context.17, 18, 19 Finally, few fruit and vegetable consumption TPB studies have examined potential moderating variables within the theory, and there are none from a 5-A-Day perspective. Identifying potential moderating variables will be very important to better tailor a potential 5-A-Day intervention to the needs of multiple demographic groups simultaneously. Two moderator variables that researchers have suggested to examine when addressing fruit and vegetable consumption are gender and ethnicity.10, 14, 20 Unfortunately, the aforementioned studies produced inconclusive results pertaining to gender, suggesting the need for further examination, particularly within the TPB. Additionally, no studies have examined the role of ethnicity within the TPB from a fruit and vegetable perspective. However, physical activity studies in the college population have shown that the affective attitude/intention relationship is significantly stronger for black students when compared to white students, and the instrumental attitude/intention relationship is significantly stronger for white students when compared to black students.17, 21 Additionally, the strength of the intention/PA relationship has also been shown to be moderated by ethnicity (ie, the relationship was significantly stronger for white students compared to black students).21 Therefore, examining the moderating role of gender and ethnicity within the TPB is warranted.

The primary purpose of the present study was to examine the utility of the global TPB constructs in explaining fruit and vegetable consumption from a 5-A-Day perspective in a college sample over a 1-week period. Based on the research outlined above, it was hypothesized that subjective norm and perceived behavioral control would significantly predict 5-A-Day intentions. However, as previous TPB studies related to fruit and vegetable consumption have not differentiated affective and instrumental attitude, it was hypothesized that affective attitude would be the dominant attitudinal predictor of 5-A-Day intention based on physical activity research. Finally, given the contradictory results pertaining to the relationships between fruit and vegetable consumption and intention/perceived behavioral control, it was hypothesized that both would significantly predict 5-A-Day consumption.

The second purpose of the present study was to determine whether any of the TPB relationships regarding 5-A-Day were moderated by gender and ethnicity. As previous research has been inconsistent regarding the role of gender and ethnicity within the TPB from a fruit and vegetable perspective,10, 14 the null hypothesis was tested (ie, gender and ethnicity would not moderate the TPB relationships).

Section snippets

Participants

The initial sample (N = 511) was obtained from a variety of undergraduate fitness and health classes from 2 universities. They had a mean age of 19.8 years (SD = 2.7 years) and a mean body mass index (BMI) of 24.0 (SD = 4.7). Additionally, 49.7% were female, and 29.0% were employed. The students were primarily black (47.2%) or white (39.1%), and the remaining 13.5% were Asian and Hispanic students. The majority (64%) lived in a dorm, whereas the remaining students lived in an off-campus

Results

In total, 541 students were invited to participate, and 511 (94.5%) agreed to do so. The reasons provided for nonparticipation pertained to lack of time and interest. Although complete data were available at baseline for all 511 participants, 95 participants (18.6%) did not complete the 1-week fruit and vegetable assessment because of nonattendance at follow-up. The missing value analysis showed that the follow-up fruit and vegetable assessment was missing at random. Unfortunately, using

Discussion

The primary purpose of this study was to determine whether the TPB explained intentions and consumption of 5 servings of fruits and vegetables per day in a college sample over a 1-week period. The hypothesis that affective attitude would be the dominant attitudinal predictor was supported. Although this finding is novel to the TPB literature from a fruit and vegetable perspective, it is consistent with a growing body of TPB/physical activity literature.17, 18, 19 Such a finding suggests the

Implications for Research and Practice

Notwithstanding the above limitations, the present study demonstrated that affective attitudes and perceived behavioral control are significant predictors of 5-A-Day intention, which in turn is a significant predictor of 5-A-Day behavior in a college sample. Furthermore, the magnitude of these effects was the same for male versus female and black versus white students; however, females and blacks had much more positive beliefs than males and whites about fruit and vegetable consumption. Given

Acknowledgment

This project was supported by a Research Centers in Minority Institutions award, #G12RR03062, from the National Center for Research Resources, National Institutes of Health.

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