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Examine intentions to buy and eat dark green leafy vegetables (DGLV).
Cross-sectional survey assessing demographics, behavior, intention, and Reasoned Action Approach constructs (attitude, perceived norm, self-efficacy).
Marion County, Indiana.
African American women responsible for buying and preparing household food.
Reasoned Action Approach constructs explaining intentions to buy and eat DGLV.
Summary statistics, Pearson correlations, and multiple regression analyses.
Among participants (n = 410, mean age = 43 y), 76% and 80%, respectively, reported buying and eating DGLV in the past week. Mean consumption was 1.5 cups in the past 3 days. Intentions to buy (r = 0.20, P < .001) and eat (r = 0.23, P < .001) DGLV were positively associated with consumption. Reasoned Action Approach constructs explained 71.2% of the variance in intention to buy, and 60.9% of the variance in intention to eat DGLV. Attitude (β = .63) and self-efficacy (β = .24) related to buying and attitude (β = .60) and self-efficacy (β = .23) related to eating DGLV explained significant amounts of variance in intentions to buy and eat more DGLV. Perceived norm was unrelated to either intention to buy or eat DGLV.
Interventions designed for this population of women should aim to improve DGLV-related attitudes and self-efficacy.
Increased consumption of fruits and vegetables (FV) may help decrease disparities in diet-related health outcomes.1 However, vegetable consumption in the US is low, and only 26% of adults meet national recommendations.2,3 Vegetable consumption is even lower among minority populations (ie, Mexican Americans and African Americans [AA] relative to Whites).4 Vegetables in the “dark green” group, as identified by the US Department of Agriculture, are both cruciferous and leafy (eg, spinach, broccoli, romaine lettuce, watercress, Swiss chard, kale, collard, and mustard greens). Although they are the most nutritious group, dark green vegetables are also the least consumed.5–7 They are rich sources of vitamins A and C, folate, and β-carotene, and they provide numerous health benefits (eg, reduced risk of cardiovascular diseases).7–10 The importance of consuming dark green leafy vegetables (DGLV) is highlighted in the US Department of Health and Human Services National Healthy People 2020 policy statement (ie, increase the proportion of dark green vegetables consumed by Americans) and the Dietary Guidelines for Americans (ie, women should consume 1.5 cups of DGLV per week, and men should consume 1.5–2 cups per week).5,8,11
The diets of AA have been of particular interest to researchers; Kirkpatrick, Dodd, Reedy, and Krebs-Smith posited that such racial minority populations could potentially benefit from eating more DGLV.4,12–15 There is no single “typical” eating pattern to which all AA ascribe,13 and studies indicate that DGLV are common in the AA culture and have been since the Atlantic slave trade. Specifically, during this time, dark green vegetables (eg, spinach and various types of greens) and other vegetables (eg, sweet potatoes, okra, squash) were brought from Africa to America.16–19 Although DGLV remain an important and cultural component of some AA diets, determinants of their consumption have yet to be fully understood.20–22 To identify these determinants, it has been recommended that DGLV be studied separately from fruit and other types of vegetables (eg, red, orange), a practice not often reported in the literature.23
Although an examination of DGLV eating behaviors is important, there is an expressed need to examine behavioral domains beyond eating,14 given that eating is the most distal behavior relative to buying and preparing food.24 African American women have been described as being household “gatekeepers” who are primarily responsible for buying and preparing food.25 They often take pride in this role and have intentions to share food among family, friends, and those who are in need.26 These notions support findings that characterize AA women as dietary change agents who influence familial consumption of healthful food such as FV.12,13,27,28 Therefore, the current study sought to expand the DGLV evidence base by using behavior change theory to explore intrapersonal factors associated with intentions to buy and eat more DGLV among a sample of midwestern AA women who buy and prepare household food.
The Reasoned Action Approach (RAA) is a theoretical model of behavior change that has been used to identify beliefs underlying people's behavioral decisions. The theory is the latest formulation of the Theory of Planned Behavior, and it assumes that one's intention is the most immediate predictor of behavior.29 According to the RAA, there are 3 global constructs that determine one's intention to perform a behavior: (1) attitude toward a behavior; (2) perceived norms about performing a behavior; and (3) self-efficacy about performing a behavior.29,30 The RAA and its constructs have been used to understand behaviors associated with obesity and chronic disease prevention,31,32 as well as determinants of AA fruit and vegetable consumption.14,33,34 Such studies have supported the use of RAA constructs in explaining general variations in FV consumption among AA, but few studies have focused specifically on DGLV in this population.
In this study, the RAA was used to understand a sample of AA women's intentions to perform 2 behaviors: (1) eat more cups of DGLV each week over the next 3 months; and (2) buy more DGLV each week over the next 3 months. When using the RAA, behaviors are defined in terms of the target, action, context, and time.35 Intention to eat and intention to buy are the chosen action elements. “More” (vs a specific number of cups) was selected as the target to reflect Healthy People 2020's recommendation to eat a higher proportion of DGLV.11 Given that DGLV recommendations are based on weekly consumption, “each week” is the context.5 “Three months,” which has been used in previous RAA research, was chosen as an appropriate time interval to initiate behavior change.20,22
Participants were recruited from 8 local community and professional organizations, health clinics, and faith-based institutions. Recruitment methods varied by site and included personal contact and flyers at sites and announcements at meetings and services. Inclusion criteria were: AA; female; 18 years of age or older; resident of Marion County, Indiana; and primarily responsible for buying and preparing household food. Eligible women read and signed the study consent form. Participants were provided with a survey and a Dark Green Leafy Vegetable Guide to assist with the identification and measurement of DGLV. The guide was pilot-tested with members of the target population (n = 30) who did not participate in the current study. Revisions were made accordingly to enhance comprehension. As incentives to participate in the study, participants were given a $10 supermarket gift card and were allowed to keep the Dark Green Leafy Vegetable Guide after completing the survey. Study procedures were approved by the Institutional Review Board at Indiana University.
Participants who were eligible and had given consent took part in the self-administered, cross-sectional survey. The survey assessed demographics, health status, food-related practices and preferences, DGLV purchasing and consumption, behavioral intention, and RAA global constructs (ie, attitude, perceived norm, self-efficacy). Geolocation data for participant household and preferred food store were obtained but are beyond the scope of the current analysis. The study survey was pilot-tested (n = 5) to ensure participants could understand the content, and it was revised as needed.
Demographic items were developed based on a review of relevant literature, and consisted of age, highest grade level or years of education completed, total household income last year, receipt of assistance from the government to buy food, number of adults and children living in the household, and height and weight. Participants were asked whether a doctor, nurse, or other health professional had ever told them that they had any of 6 chronic health conditions (eg, high blood pressure, heart disease, diabetes, cancer). Participants were also asked about their home food–related practices and preferences (eg, “Does your household eat the primary meal of the day together?”) and whether or not members of their household liked DGLV (ie, “How many of the people that you cook for in your household like dark green leafy vegetables?”).
Participants were asked whether they had purchased DGLV in the past 7 days. To ascertain consumption, participants were asked to report whether they had eaten at least 1 type of DGLV in the past 7 days. They were then asked to recall the past 3 days and report the number of cups of raw DGLV they had eaten (ie, “How many cups of DGLV did you eat yesterday, the day before yesterday, and the day before that?”). The same questions were asked for cooked DGLV. A 3-day time frame was selected, given that similar participants in a pilot study had difficulty completing a DGLV 7-day recall.20 Consumption of 2 cups of raw DGLV equates to 1 cup of cooked DGLV,8 and cooked DGLV was summed to obtain total DGLV consumption.
Direct RAA items for attitude, perceived norm, and self-efficacy were developed from earlier belief elicitation research with members of the target population not included in the current study.20 Reasoned Action Approach survey items consisted of a 3-item measure of intention, a 2-item measure of attitude, a 2-item measure of perceived norm, and a 3-item measure of self-efficacy to buy and eat more DGLV, respectively, each week over the next 3 months. Although it is recommended that a minimum of 3measures be used to assess RAA constructs,36 2-item measures for attitude and perceived norm for eating and buying, respectively, were selected to keep the survey completion time to 40 minutes. Inclusion of fewer than 3 Theory of Planned Behavior/RAA measures has been used for the examination of FV consumption28 and other health behaviors.32,37
Intention was measured through agreement with statements assessing the likelihood of performing each behavior using two 5-point scales ranging from 1 (extremely unlikely) to 5 (extremely likely) and 1 (strongly disagree) to 5 (strongly agree). For intention to buy more DGLV each week for the next 3 months, the statements were: “Is it likely that you will buy more DGLV each week over the next 3 months?” “I will buy more DGLV each week over the next 3 months,” and “My buying more DGLV each week over the next 3 months is likely.” Similar items were used to assess intention to eat more cups of DGLV. Measures of intention to buy and eat, respectively, were calculated by averaging the 3 items.
Attitude toward action of buying was measured with ratings of the statements pertaining to buying more DGLV each week over the next 3 months and eating more cups of DGLV each week over the next 3 months on two 5-point semantic differential scales ranging from 1 (extremely unenjoyable) to 5 (extremely enjoyable) and 1 (extremely bad) to 5 (extremely good). Similar items measured attitudes about eating more DGLV over the next 3 months. Measures for attitudes about buying and eating, respectively, were calculated by averaging the 2 items.
Perceived norms were assessed by agreement with statements about what participants' salient referents thought about buying and eating more cups of DGLV, respectively, each week over the subsequent 3 months. On a 5-point scale that ranged from 1 (strongly disagree) to 5 (strongly agree) for buying, participants rated the statements “Most people who are important to me think that I should buy more DGLV each week over the next 3 months,” and “Most people like me will buy more DGLV each week over the next 3 months.” For eating, similar items were constructed. Measures for perceived norms about buying and eating were calculated by averaging the 2 items.
Self-efficacy was based on responses from 3 items, 1 difficult/easy rating on a 5-point scale from 1 (extremely difficult) to 5 (extremely easy) and two 5-point scales from 1 (strongly disagree) to 5 (strongly agree). For buying more DGLV over the next 3 months, participants rated the statements as follows: “Buying more DGLV each week over the next 3 months is difficult/easy,” “It is up to me to buy more DGLV each week over the next 3 months,” and “I am sure that I can buy more DGLV each week over the next 3 months.” Similar items were used to assess self-efficacy to eat more cups of DGLV. An overall measure of self-efficacy for buying and eating, respectively, was calculated by averaging the 3 items.
Summary measures were used to describe the participants and their DGLV buying and eating behaviors. Reliability analysis and exploratory factor analysis were conducted to understand the internal consistency of the items measuring RAA global constructs and to identify associations among constructs. Bivariate (Pearson) correlation coefficients were computed for associations between the 2 behaviors' psychosocial constructs for intention, attitude, perceived norm, and self-efficacy to buy and eat more DGLV. Bivariate correlations were also computed for the association between intention and actual consumption. Two hierarchical multiple regression analyses were conducted to determine the significance of the RAA global constructs in explaining intention for buying and eating more DGLV. As the dependent variable was intention to buy more DGLV, the independent variables were entered into the “buying” regression model in the following order: 3-item self-efficacy, 2-item perceived norm, and 2-item attitude. The same order was used for the “eating” regression model. A value of P < .05 was considered statistically significant.
A convenience sample of 410 women with a mean age of 43 years (SD = 15.7) consented to be in the study. Additional participant and household data are in Table 1.
Seventy-six percent of women in the study reported that they had bought DGLV within the past 7 days. On average, participants ate 1.5 cups of DGLV in the past 33 days, and 80% ate at least 1 type of DGLV in the past 7 days. Two thirds of participants indicated that members of their household eat their primary meal of the day together. When asked about members of their household, 62% perceived that “everyone liked DGLV.”
Reliability analyses indicated that for buying more DGLV, there was high reliability for the 3-item measure of intention (Cronbach α = .94), 2-item measure of attitude (Cronbach α = .84), and 3-item measure of self-efficacy (Cronbach α = .79). The reliability of the 2-item measure of perceived norm was low (Cronbach α =.64). Similarly, for eating more DGLV, there was high reliability for the 3-item measure of intention (Cronbach α = .91), 2-item measure of attitude (Cronbach α = .84), and 3-item measure of self-efficacy (Cronbach α = .79). The reliability of the 2-item measure of perceived norm was low (Cronbach α = .57).
Mean responses for intention to buy (mean = 4.1, SD = 0.90) and eat (mean = 3.9, SD = 0.94) DGLV were high. Small, but significant, positive associations were found between DGLV consumption and intention to buy (r = 0.20, P < .001) and intention to eat (r = 0.23, P < .001) DGLV.
Significant positive correlations with intention to buy were revealed for attitude toward buying (r = 0.83, P < .001), perceived norm about buying (r = 0.44, P < .001), and self-efficacy for buying (r = 0.73, P < .001). Similarly, significant positive correlations with intention to eat were revealed for attitude toward eating (r = 0.77, P < .001), perceived norm about eating (r = 0.33, P < .001), and self-efficacy for eating (r = 0.65, P < .001). For both buying and eating behaviors, attitude showed the highest correlation with behavioral intention and the weakest with perceived norm. In comparing the 2 behaviors with respect to the RAA variables, significant positive correlations were found for intention (r = 0.72, P < .001), attitude (r = 0.70, P < .001), perceived norm (r = 0.52, P < .001), and self-efficacy (r = 0.66, P < .001). In other words, intention to buy DGLV was strongly associated with intention to eat DGLV; attitude toward buying DGLV was strongly associated with attitude toward eating, and so on.
Table 2 presents the results of the multiple regression analysis for variation in the dependent variable (ie, behavioral intention) related to the 3 global RAA constructs. For intention to buy and intention to eat DGLV, unstandardized regression coefficients (B), standard errors (SE B), standardized regression coefficients (β), t values, and P are presented. With an R of 0.84, RAA global constructs explained 71.2% of the variance (F[3, 403] = 331.708, P < .001) in intention to buy more DGLV. In explaining intention to buy, both attitude (β = .63) and self-efficacy (β = .24) had significant weights. Similarly, with an R of 0.78, the RAA global constructs explained 60.9% of the variance (F[3, 403] = 209.611, P < .001) in intention to eat more DGLV. In explaining intention to eat more DGLV, both attitude (β = .60) and self-efficacy (β = .23) had significant weights. Whereas the bivariate correlations between perceived norm and intention to buy and eat more DGLV were significant, the regression weights for perceived norm were not significant in the multivariate analyses.
In this sample of low- to moderate-income AA women residing in Marion County, Indiana (located in the mid-western region of the US), results indicated that most participants (80%) ate DGLV in the past 7 days and, on average, reported adequate intakes (ie, 1.5 cups in the past 3 days). Female sex and higher education level (ie, 57% completed at least 1 year of college) have been associated with general FV consumption in other samples.38,39 As previously noted, studies have identified DGLV to be commonly consumed among some, though not all, populations of AA. Although beyond the scope of the current study, regionally specific cultural practices should be assessed in the future, as they could contribute to a better understanding of DGLV intakes across different AA samples.16–18,40
Behavioral intention is an important determinant of nutrition-related behaviors,41 and participants in this study had strong intentions to buy and eat more DGLV each week over the subsequent 3 months. Yet correlations between reported consumption and intention to buy (r = 0.20, P < .001) and intention to eat (r = 0.23, P < .001) more DGLV were relatively low. Given that intention was assessed in terms of eating and buying “more” DGLV (vs a specific amount), intentions may differ if a more stringent behavioral criterion is applied. Additionally, the weakness of the behavior–intention associations not only supports the notion that one's intention to perform a behavior may not lead to action, but also highlights the need to consider other factors—some of which, such as local access or quality, may go beyond the individual.20,21,42
The current study's results also show that the stronger the intentions women had for each behavior, the stronger their attitudes and self-efficacy were about performing the behaviors of interest. Further, intention, attitude, and self-efficacy to buy were strongly associated with intention, attitude, and self-efficacy to eat. For both behaviors, attitude had the greatest weight in explaining intention, as the weight for self-efficacy was somewhat smaller. Although perceived norm was significantly associated with intention, it was not significant in the final regression analyses for either behavior. Study results for attitude and self-efficacy are consistent with previous research identifying them as important intrapersonal constructs for AA and other racial/ethnic groups' intentions to eat fruit, vegetables, and other healthful food.33,43–45
On the one hand, the significant correlation of perceived norm with intention is consistent with research showing that spouses and other family members influence food choices and purchasing among AA and other groups.12,46 On the other hand, the multivariate finding that perceived norm did not contribute when attitude and self-efficacy were considered is consistent with studies examining more general fruit and vegetable consumption47 and intention to eat healthier food.48 Clearly, the role of perceived norm deserves further attention.
The study results suggest that RAA-based interventions designed to promote increased buying and consumption of DGLV for AA women living in this region of the US may be more effective if they focus primarily on changing attitudes and increasing self-efficacy. For example, improving attitude may be addressed by identifying and addressing beliefs held by AA women about the advantages and disadvantages of buying and eating more DGLV. Self-efficacy may be addressed by improving skills related to buying and eating, such as cooking demonstrations and the provision of recipes showing healthy ways to prepare DGLV. Self-efficacy may also be addressed by altering features of the environment that make DGLV more accessible and easier to buy. In order to improve attitudes and self-efficacy about eating and buying more DGLV, a greater understanding of why these vegetables are healthful by the population of interest may be required, as well. For example, Lynch, Holmes, Keim, and Koneman found that among a sample of AA women, explanations of why and which food items are healthful differed within the sample.49
The use of qualitative methods to understand decisional processes around the behaviors of interest, such as those used by Reicks and colleagues, may also provide insight.50 Such strategies to understand and address attitudes and self-efficacy highlight the potential for integrative, multilevel public health interventions and/or campaigns designed to reach the target population. Finally, studies have shown strong positive associations between significant others/caregivers buying and preparing healthy food and family members (eg, men, adolescent girls) subsequently eating and purchasing healthy food.25,51 With over half of the sample reporting children living in their household, most participants perceived that all household members liked DGLV, and nearly two thirds of households ate their primary meal of the day together. These observations suggest that interventions that stimulate increased DGLV-related behaviors among this population may have particularly positive implications for other household members, relative to other populations. Given that family support has had a significant influence on eating behaviors of AA women, it may be beneficial to target and/or include household members in dietary intervention programs, as well.52
This study has several limitations. First, the study was cross-sectional, so causation cannot be inferred. Second, a sample of convenience was used, and study results should not be generalized beyond the characteristics of the group under study. Third, the relatively weaker reliability of the perceived norm measures may have had an impact on study the results. Following methods described by Fishbein and Azjen,29 for each behavior, there was an injunctive item about what other people think (eg, “Most people who are important to me think that I should buy more DGLV each week over the next 3 months”) and descriptive item about what other people do (eg, “Most people like me will buy more DGLV each week over the next 3 months”). Although they both make up perceived norm, they are slightly different facets. Therefore, to improve reliability, additional injunctive and descriptive items could be developed for each behavior. Fourth, data were collected during the summer months, which may have increased the number and variety of DGLV available. Finally, the dependent variables for the regression models were behavioral intentions to eat and to buy DGLV, and they may not be strongly linked with the actual behaviors of interest.
Limitations notwithstanding, the current study addressed a number of gaps in the literature by focusing on a less-often-studied subgroup of vegetables; examining factors potentially linked with buying and eating DGLV among AAs; and using a theory-based survey instrument. The RAA measures showed acceptable reliability,53,54 and research demonstrates that intention is often a reasonable predictor of behavior in many, though not all, cases.29 Although the authors acknowledge the contributions of social-ecological frameworks55 to the understanding of AA consumption of FV, this study, as far as it can be determined, is unique in its application of theory to identify intrapersonal determinants of buying and eating more DGLV among the study's target population. Thus, the primary implication of the study is that the RAA is appropriate for explaining intention to buy and intention to eat more DGLV among a sample of midwestern AA women. In an effort to build on the information obtained from the current results, future research should identify how the constellation of constructs assessed in this investigation could predict current and future DGLV buying and eating patterns in this population.
The authors would like to acknowledge Millicent Fleming-Moran, PhD, and staff at the Marion County Health Department; Ruth Lambert, PhD; LaWanda Lambert Girton; Terry Curtis; Dr. Linda Johnson; Brittany Baird; and Darleesa Gates-Doss, PhD, MPH for assistance in accessing the target population, the provision of resources, and/or technical assistance. Dr. Sheats is supported by US Public Health Service grant T32 HL007034 from the National Heart, Lung, and Blood Institute and Stanford University.