Pricing Strategies to Encourage Availability, Purchase, and Consumption of Healthy Foods and Beverages: A Systematic Review
SYSTEMATIC REVIEW — Volume 14 — November 2, 2017
Joel Gittelsohn, PhD1; Angela Cristina Bizzotto Trude, MS1; Hyunju Kim, MPH1 (View author affiliations)
Suggested citation for this article: Gittelsohn J, Trude ACB, Kim H. Pricing Strategies to Encourage Availability, Purchase, and Consumption of Healthy Foods and Beverages: A Systematic Review. Prev Chronic Dis 2017;14:170213. DOI: http://dx.doi.org/10.5888/pcd14.170213.
Food pricing policies to promote healthy diets, such as taxes, price manipulations, and food subsidies, have been tested in different settings. However, little consensus exists about the effect of these policies on the availability of healthy and unhealthy foods, on what foods consumers buy, or on the impact of food purchases on consumer health outcomes. We conducted a systematic review of studies of the effect of food-pricing interventions on retail sales and on consumer purchasing and consumption of healthy foods and beverages.
We used MEDLINE, Embase, PsycINFO, Web of Science, ClinicalTrials.gov, and the Cochrane Library to conduct a systematic search for peer-reviewed articles related to studies of food pricing policies. We selected articles that were published in English from January 2000 through December 2016 on the following types of studies: 1) real-world experimental studies (randomized controlled trials, quasi-experimental studies, and natural experiments); 2) population studies of people or retail stores in middle-income and high-income countries; 3) pricing interventions alone or in combination with other strategies (price promotions, coupons, taxes, or cash-back rebates), excluding studies of vending-machine or online sales; and 4) outcomes studies at the retail (stocking, sales) and consumer (purchasing, consumption) levels. We selected 65 articles representing 30 studies for review.
Sixteen pricing intervention studies that sought to improve access to healthy food and beverage options reported increased stocking and sales of promoted food items. Most studies (n = 23) reported improvement in the purchasing and consumption of healthy foods or beverages or decreased purchasing and consumption of unhealthy foods or beverages. Most studies assessed promotions of fresh fruits and vegetables (n = 20); however, these foods may be hard to source, have high perishability, and raise concerns about safety and handling. Few of the pricing studies we reviewed discouraged purchasing and consumption of unhealthy foods (n = 6). Many studies we reviewed had limitations, including lack of formative research, process evaluation, or psychosocial and health assessments of the intervention’s impact; short intervention duration; or no assessment of food substitutions or the effects of pricing interventions on food purchasing and diets.
Pricing interventions generally increased stocking, sales, purchasing, and consumption of promoted foods and beverages. Additional studies are needed to differentiate the potential impact of selected pricing strategies and policies over others.
Pricing strategies to encourage the availability, purchasing, and consumption of healthy foods and beverages have received increased attention in the past decade, in the United States and worldwide. Various pricing strategies have been studied in different settings, including taxes and price manipulations of sugar-sweetened beverages (SSBs), high calorie–low nutrient foods or foods high in added sugars or saturated fats, and subsidies of fruits and vegetables. Despite these studies, little consensus exists about the effectiveness of these pricing strategies in changing the availability and affordability of healthy and unhealthy foods or their effect on consumer outcomes (ie, foods purchased, foods consumed, and health). Furthermore, little consensus exists about how pricing strategies function, alone or combined with health behavior interventions or as part of multi-level interventions.
Reviews were conducted previously on related topics. Nine recent reviews (from 2010 through 2015) examined the effect of taxes, subsidies, or their pooled effect on food consumption, consumer purchases, body weight, or diet-related chronic diseases (1–9). However, many of these reviews described laboratory-based or simulation studies (6–8). Only one systematic review described field intervention studies (9) and focused on subsidies to increase purchasing of healthy foods. Few focused on implementation and outcomes of pricing interventions at both the supply (retail) and demand (consumer) levels in actual communities.
Decision makers need a systematic review of the effectiveness of pricing incentives and disincentive strategies on availability, purchasing, and consumption of healthy and unhealthy foods and beverages at the consumer and retail levels. Therefore, our goal was to answer the following questions: 1) How do pricing incentives and disincentives influence access, purchasing, and consumption of healthy and unhealthy foods and beverages among various populations in high-income and middle-income countries? 2) What additional work is needed to enable communities, states, and countries to identify the best combination of strategies?
We conducted a systematic review of English-language, peer-reviewed articles describing studies that evaluated the effectiveness of pricing incentives and disincentive strategies on purchasing and consumption of healthy and unhealthy foods and beverages in high-income and middle-income countries in various socioeconomic settings. We searched 6 electronic databases — MEDLINE, Embase, PsycINFO, Web of Science, ClinicalTrials.gov, and the Cochrane Library — from January 2000 through December 2016 for relevant studies.
We developed a search strategy based on medical subject heading (MeSH) terms and based on the text and key words of key articles we identified a priori (Appendix). We used Boolean operators to combine keywords and MeSH terms for a focused search. We developed 3 topics based on our research question (incentive/disincentive, food intake, and food purchasing), and we then included key words and MeSH terms representing each term. Search terms were pricing strategies, incentive, reimbursement, commerce, disincentive, reward, taxes, monetary incentive, consumer behavior, marketing, cost savings, food purchasing, food supply, dietary intake, eating behavior, food intake, food and beverages, and snacks.
We selected the following types of human studies published in English in peer-reviewed journals, from 2000 through 2016: 1) experimental studies (randomized controlled trials, quasi-experimental studies, and natural experiments, excluding reviews and cross-sectional, qualitative, and simulation models studies); 2) population studies of people or stores in middle-income and high-income countries; 3) studies of pricing interventions conducted alone or in combination with other strategies (price promotions, coupons, taxes, or cash-back rebates), excluding studies of vending-machine or online sales; and 4) outcomes studied at the retail (stocking, sales) or consumer (purchasing, consumption) levels. Additional criteria were that study outcomes were assessed at the retail level (stocking, sales) or consumer level (purchasing, consumption) and that the study was not an evaluation of a government program in schools (eg, a school-based food assistance program).
Two reviewers (A.C.B.T., H.K.) reviewed abstracts and full articles independently to assess eligibility for inclusion. H.K. confirmed or corrected A.C.B.T.’s data abstractions for completeness and accuracy. We also conducted a reference list search on the studies we selected for review and identified 5 eligible studies. Lastly, we identified all peer-reviewed publications associated with each study and cited only those that contributed to this review.
For the synthesis, we employed an adjudication approach. We used a series of descriptive criteria to characterize each study: project name, target population, model or theory, study goal, foods and beverages that were the intervention’s focus and its retail venue, sample size, intervention strategies, study design, study duration, formative research, feasibility assessment, process evaluation, impact measures and results, sustainability, quality of research, study limitations, and study recommendations (Appendix Table 1). Two reviewers (A.C.B.T., H.K.) analyzed each study independently and provided a long and a short response for the descriptive criteria. A third reviewer (J.G.) reviewed the descriptions and agreed or disagreed to the study’s inclusion. Where there was disagreement, the third reviewer broke the tie.
We organized data into the following categories: 1) a description of each study; 2) a description of the intervention, pricing strategies, and the study evaluation; and 3) main results and study implications. Data were then grouped by type of pricing intervention categories: 1) financial discount on healthy foods and beverages, 2) redeemable coupons or vouchers for healthy foods and beverages targeting participants in food assistance programs, 3) redeemable coupons or vouchers for healthy foods and beverages targeting consumers not participating in food assistance programs, 4) cash rebates, and 5) disincentive strategies for unhealthy food and beverage purchases (eg, tax, alone or combined with a strategy promoting healthy foods).
Searches returned 2,076 articles, and 1,677 were screened after excluding duplicates (ie, the same article in different research databases) and by refining the searches by year, language, and species. After elimination of 1,625 for not meeting our study criteria, 52 were fully assessed for eligibility; 27 were excluded and 5 were included after a reference list search. Thus, 30 distinct studies in 63 articles were included in the final analysis (Figure). The number of peer-reviewed publications per study varied from 1 to 7, with a median of 2 per study.
Description of studies
The 30 studies included in the review were conducted in 9 countries: the United States (n = 17), Australia (n = 2), New Zealand (n = 2), France (n = 2), Canada (n = 1), the United Kingdom (n = 1), South Africa (n = 1), Denmark (n = 1), Belgium (n = 1), Peru (n = 1), and Mexico (n = 1) (Table 1). The largest number of studies (n = 8) took place in the northeastern United States (Table 1). Most studies (n = 18) did not report the use of a theoretical model. Of the 12 that did, social cognitive theory was most commonly mentioned (n = 5), followed by the social ecological model (n = 5). The most common study design (n = 15) was a randomized controlled trial, with randomization either at the group or individual level.
At the consumer level, sample sizes ranged from 28 individual participants (What to Eat for Lunch study) to more than 50,000 households (Mexico excise tax study), with a median of 454 individuals sampled. Among the randomized controlled trials, the median sample size per study arm was 100 participants. The sample size or unit of randomization in some studies was based on clusters (eg, food stores) and not necessarily on individuals.
Almost all studies (n = 25) examined the impact of a pricing intervention alone or in combination with other strategies related to the stocking, sales, purchasing, or consumption of healthy foods. Most studies targeted low-income, disadvantaged populations (n = 18). Many studies (n = 12) targeted a specific population that was reached through the venue of the intervention (eg, a worksite, sports gym, school, swimming pool, hospital).
Interventions and strategies studied
Nearly all studies (n = 27) examined interventions that promoted healthy foods (Table 2). The most common types of foods promoted were fruits and vegetables (n = 20), particularly fresh produce, followed by low-sugar beverages (n = 10), and healthily prepared entrees and side dishes (n = 8). Only a few studies (n = 6) discouraged unhealthy foods, such as SSBs and foods high in saturated fat and sugar, as part of the intervention, generally by raising the prices of these foods.
The types of food sources targeted varied and included grocery stores and supermarkets (n = 7), all retailers in a setting (eg, city, neighborhood) (n = 6), farmers markets (n = 5), worksite cafeterias and school cafeterias (n = 5), food delivery services (n = 2), carryout restaurants (n = 1), corner stores (n = 1), and other types of retailers. The number of the food sources intervened in for each study also varied, from one to many thousands, because some studies implemented the strategy city-wide (median, 5 food source locations). Pricing interventions also differed between studies. Nine studies emphasized price discounts on healthy foods and beverages, ranging from 10% to 33%. Four studies provided coupons or vouchers of $5 to $20 to food assistance recipients. Six studies provided coupons or vouchers of $1 to $22 to the general population. In 5 studies, the pricing intervention was a cash rebate. The amount of the rebate took many different forms, such as a straight percentage off or a price reduction up to a certain limit. Six studies tested price increases on unhealthy foods, half of which included a price reduction on healthier foods. Three of these studies were of local or federal taxes, including taxes on SSBs.
Six of the 30 studies sought to change the availability of healthy or unhealthy foods. Only 2 of the studies changed the physical location of foods as a means of increasing their uptake by consumers. Eleven of the 30 studies implemented labeling to identify healthy versus unhealthy food choices. Most labeling approaches occurred in studies (n = 8) centered on the promotion of healthy foods and beverages. Five of the 30 studies used a policy approach, and 4 studies involved taxes at the city or national level.
Most studies (n = 17) reported no formative research (Appendix Table 2). When formative research was conducted, it consisted of qualitative information gathering (n = 3), structured survey data collection (n = 4), or a pilot study (n = 6).
Most studies (n = 20) reported conducting a feasibility assessment, which consists of assessment of economic or cultural acceptability, operability, or perceived sustainability. However, feasibility assessment varied greatly among studies in terms of rigor and scope.
Process evaluation assesses how well an intervention was implemented according to the study plan and is usually assessed in terms of reach, dose delivered, and fidelity (75). Most studies (n = 18) reported no process evaluation. Two studies reported conducting extensive process evaluations that assessed reach, dose delivered, and fidelity (10,19).
Most studies (n = 20) assessed the impact of the intervention at the retail level (Table 2). Of these 20 studies, 15 collected data on sales of specific promoted foods. Other studies looked at changes in revenues, food availability, purchasing data, and changes in prices, although these measures were used in only 2 studies (36,40).
We examined impact assessment at the consumer level in 3 different domains: psychosocial, behavioral, and health outcomes. More than half (n = 17) of the studies reviewed included no consumer-level psychosocial assessment. Of those that did, measures used varied and included knowledge, self-efficacy, intentions for healthier behaviors, perceived healthfulness of the diet and affordability of healthy foods, perception of barriers to eating healthy, and food security.
Most studies (n = 24) described consumer-level behavioral assessment, most often measurements of food purchasing and consumption. Only 10 of the 30 studies reviewed measured any type of consumer-level health outcome. Most commonly, change in body mass index (BMI [kg/m2]) was assessed (7 studies), followed by blood work (4 studies).
Study results reported and study implications
We found little consistency in study results reported for feasibility and process measures (Appendix Table 2). Where reported, feasibility of pricing interventions was moderate to high. Pricing interventions were acceptable and generally were implemented as planned. In 1 study (21), the pricing intervention was not implemented at any site because of food managers’ concerns about profit loss. Where extensive process results were reported (2 studies), implementation quality was generally described as moderate (10,19).
Of the studies (n = 21) that measured an intervention’s impact at the retail level, the most common effects reported were increased sales of healthy foods (7 studies) (11,19,20,35,45,58,59, improved revenues or total profits (4 studies) (11,25,36,40), increased stocking of healthier foods (4 studies) (19,21,26,74, decreased sales of unhealthy foods (3 studies) (25,64,68), and increased sales of healthy foods as a ratio to unhealthy foods (2 studies) (10,55) (Table 3). All 16 studies that reported effects at the retail level found a positive impact on either stocking or sales. In summary, sales of units of healthy foods and beverages increased from 15% (19) to 1,000% (25), and sales of unhealthy foods and beverages decreased from 5% (64) to 47% (69). Stocking of healthy foods increased from 40% (19) to 63% (26) in response to pricing interventions (Table 3).
Only 13 studies reported any assessment of the impact of interventions on consumer psychosocial factors. Four studies found improved perceptions related to healthy eating (27,37,56,74). Three studies indicated that consumers improved their perception of healthfulness or availability of fruits and vegetables (36,45,60). Two studies found that consumers were more likely to shop at farmers markets (36,43).
Most (n = 23) studies assessed the impact of interventions on consumer behavior. Thirteen studies found increases in the consumption of healthy foods and beverages associated with the intervention (36–38,40,41,43,51,54,56,58,62,65,73), and 8 studies found increases in purchasing of healthy foods (10,26,27,31,35,53,54,59). Four studies found a reduction in the purchasing of unhealthy foods (52, 67, 71, 73). Four studies found a reduction in the consumption of unhealthy foods (55, 56, 64, 72). Two studies reported no effect on healthy food purchasing (44,45), and 1 found no impact on healthy beverage consumption (27). Overall, the pricing interventions, alone or in combination with other approaches, appeared to be successful in changing consumer behavior.
Although few studies (n = 8) assessed health-related outcomes at the consumer level, 5 found no impact on weight (20,22,26,41,58); 2 found no impact on various serum vitamin measures when comparing control and intervention groups over time (41,51).
Of the 14 studies that reported on sustainability of the intervention, 10 stated moderate to high sustainability through statewide or citywide implementation of the intervention (11,40), food policies that are still in progress (62,68), and continued interest of the participants (21,31,36,38,52,74).
The mean score for quality of research measures was 6.9 (standard deviation, 2.0), on a scale of 0 to 10 points (Table 3). Randomized controlled trials received higher scores than studies without a comparison group. Common study limitations included short intervention duration, possible biases in self-reporting, use of nonvalidated assessment tools, and lack of power and external validity of the findings.
To our knowledge, this is the first systematic review to evaluate the effectiveness of pricing incentives and disincentive strategies on availability, purchasing, and consumption of healthy and unhealthy foods and beverages in various settings, including field intervention studies and natural experiments. The various pricing intervention strategies that sought to improve access to healthy food and beverage choices were successful. This result has been reported by other systematic reviews where subsidies on fruits and vegetables increased the purchasing and consumption of healthy foods (2,76,77). However, only one study evaluated the impact of fruit and vegetable subsidies from the perspective of retailers (74). Findings that the pricing interventions generally increased stocking and sales of promoted foods and beverages are encouraging. There is a need to consistently demonstrate these effects (particularly in terms of sales and revenues), to build support from food retailers and vendors. We recommend that additional studies be conducted to demonstrate beneficial effects of pricing interventions on sales, and especially on profits and total retail revenues.
Pricing intervention strategies appeared to positively affect consumer-level behavior, with most studies reporting increases in purchasing and consumption of healthy foods or beverages or decreased purchasing and consumption of unhealthy foods or beverages. We found no strong pattern to indicate that one type of pricing intervention worked better than another — all appeared to be effective. Additional studies and meta-analyses are needed to differentiate the potential impact of particular pricing interventions and policies over others. Only 2 studies changed the placement of foods in a store or market to make healthy choices more evident (26,35). This strategy can be effective, particularly when coupled with a pricing intervention and should be tested in future trials.
Most studies promoted fresh fruits and vegetables. However, these foods, especially for small retailers located in low-income settings, may be hard to source, have high perishability, and raise concerns about safety and handling (12,78). In addition, it is arguable that focusing on fresh fruits and vegetables alone is unlikely to make a substantial dent in diet-related chronic diseases (79). Pricing intervention trials should be broadened to include a range of healthy foods and beverages, including frozen, and even canned, foods.
Very few studies of food pricing interventions we reviewed discouraged unhealthy foods. Formative research has revealed that it is easier to convince food source owners to optimize the purchase of healthy foods than to get them to discourage the purchase of unhealthy foods (80,81). However, without some emphasis on decreasing consumer uptake of unhealthy foods and beverages, interventions that focus on healthy foods presume a substitution effect that may not exist. An exception to this concern are taxes on junk food and SSBs that have been adopted in recent years. Additional studies are needed in real community settings, testing both subsidies of healthy foods and beverages and increased prices of unhealthy foods and beverages.
Labeling foods that are part of pricing interventions appears to be a low-cost and effective way to draw attention to these foods. However, few studies reported labeling unhealthy foods. We need additional experimental trials in community food source settings that involve labeling both healthy and unhealthy foods and beverages.
Many of the studies we reviewed were small (ie, involved fewer than 50 respondents per treatment group), which raises concerns regarding enough statistical power to detect the true effect of the intervention. Future studies should be powered to find statistical differences between evaluation groups at the food source and consumer levels. Researchers can improve the transferability of their findings by disclosing how the sample size was determined.
Few studies included in the review attempted to assess the impact of pricing interventions on health outcomes. It may be unrealistic to hope to see the impact of policy and environmental interventions of this nature on health outcomes. However, natural experiments, given sufficient study duration, may be able to assess the impact of some of the large city-based policy initiatives, such as soda taxes. The average intervention duration was less than 1 year, and most lasted only a few months. Pricing intervention studies of longer duration are needed to track effects on health outcomes, and not just at the behavioral level.
The lack of formative research for most trials is of concern, especially in those studies that targeted specific populations. Even when formative research was conducted, it was minimal and not reported in any detail. Future pricing interventions should be based on solid formative research, and these findings should be reported in the published literature. Process evaluation of any form was rarely conducted in these studies. This is a major limitation of these studies, as it is of any intervention that neglects to collect process data (75). Failure to include process evaluation means that whether the failure of the intervention was because it was inherently flawed or because the intervention was not implemented as intended cannot be understood. Process evaluation data should be collected to assess implementation for all future pricing interventions. Several studies emphasized the importance of assessing the substitution effect (using savings from discounts to purchase other less healthy foods) and the compensation effect (purchasing more healthy foods but not reducing total energy intake) of pricing interventions on food purchases and dietary intakes (28,63,70). However, such assessment was not done in any of the studies reviewed and remains a major gap in this literature. Finally, a major gap in the studies reviewed is any type of uniform attention to consumer psychosocial outcomes. We recommend developing a core set of psychosocial measures for these types of intervention trials and recommend that they be based on theoretical frameworks.
This systematic review has several limitations. First, we focused exclusively on peer-reviewed literature. It is possible that additional, unpublished trials have been conducted. Second, some of the characteristics of specific trials that we marked as “not assessed” may have been assessed (eg, conducting formative research, process evaluation, cost-effectiveness) but were not published in peer-reviewed literature. This information may have been available in gray literature reports, on websites, or in other unexamined documents and thus were not included in this review. However, our use of only peer-reviewed literature helps to ensure a reasonable quality level of the research reported. Third, the use of only peer-reviewed literature may lead to publication bias, because studies with negative or null outcomes are less likely to be published. Fourth, our quality of study criteria did not include a measure of number of community venues for implementation sites. Nevertheless, we used these criteria to ensure comparability to previous studies (77). Finally, we did not conduct a meta-analysis to evaluate the pooled effectiveness of each pricing intervention strategy. Thus, the statement that one pricing strategy was no more effective than any other is based on the synthesis of the results and should be interpreted with caution. Because each pricing intervention strategy assessed different outcomes, it was challenging to compare the effect sizes of the studies and assess treatment effect. We included many studies outside the United States to enhance generalizability.
Pricing incentives and disincentive strategies to affect access, purchasing, and consumption of healthy and unhealthy foods and beverages in high-income and medium-income countries provide an evidence-based approach to improve healthy food access at the retail level and consumer purchasing and consumption (individual-level) behaviors. Most studies reviewed promoted fresh produce, although few discouraged purchasing and consumption of unhealthy foods. Further research that uses robust study designs and measurements are needed in real community settings to simultaneously test subsidies of healthy foods and beverages and the effects of increased costs of unhealthy foods and beverages.
This research was supported by Healthy Eating Research, a national program of the Robert Wood Johnson Foundation (RWJF). The content is solely the responsibility of the authors and does not necessarily represent the official views of RWJF. RWJF had no role in study design; collection, analysis, and interpretation of data; writing the article; and the decision to submit the article for publication. We thank Dr Mary Story for her helpful comments.
Corresponding Author: Joel Gittelsohn, PhD, Johns Hopkins Bloomberg School of Public Health, Department of International Health, Global Obesity Prevention Center and Center for Human Nutrition, 615 N Wolfe St, Baltimore, MD, 21205. Telephone: 410-955-3927. Email: firstname.lastname@example.org.
Author Affiliations: 1Johns Hopkins Bloomberg School of Public Health, Department of International Health, Global Obesity Prevention Center and Center for Human Nutrition, Baltimore, Maryland.
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