Effectiveness of a Multi-Strategy Behavioral Intervention to Increase Vegetable Sales in Primary School Canteens: A Randomized Controlled Trial
Abstract
:1. Introduction
- Canteen vegetable sales in subcategories of school menus (burgers, hot meals, other hot foods, sandwiches/wraps/rolls, and snacks);
- Vegetable waste (to validate the assumption that sales are a good proxy for intake) and canteen sales revenue (as a measure of potential adverse effect);
- Acceptability of intervention strategies and implementation by canteen managers.
2. Materials and Methods
2.1. Participants
- Government, independent and Catholic primary schools (Kindergarten–Year 6) with a school canteen;
- School is located in the Greater Sydney Area;
- School canteen is using the online ordering system of a specific online provider;
- School canteen is operating at least 3 days a week;
- Principals are willing to let their school participate and are willing to share de-identified sales data (provided by the online ordering provider);
- Canteen managers are willing to implement changes to their vegetable provision and participate in a follow-up survey.
- Schools registered as a Special Needs school;
- Combined schools (K-12).
2.2. Multi-Strategy Behavioral Intervention
- Increased presence of vegetable offerings:
- A novel vegetable-containing product, ‘Rainbow Dippers’, was introduced. The product was designed and produced specifically for this study. It consisted of a vegetable-based dip and vegetable dipper (raw vegetable sticks) and was designed to contain a minimum of one serve (75 g) of vegetables. Four different flavor/color combinations were developed (e.g., carrot and celery sticks with a beetroot dip, cucumber and capsicum sticks with an avocado dip) with each combination for sale for 2 weeks during the 8-week intervention period. This product concept was positively evaluated in a qualitative study with children [20] and aligned with the CAMPOV model [20] by using bright colors, a variety of colors, bite-sized pieces, providing a fun eating experience through the dipping and using familiar and well-accepted snack vegetables. The components of the product were based on sensory consumer acceptance testing with a separate group of school aged children, with all variants being well accepted by children (data not shown). The product adhered to schools’ guidelines concerning allergies and was produced in a commercial production facility specifically for this study.
- Increased vegetable content in existing popular hot meals and foods on the canteen menu, aligning with the CAMPOV model [20] by pairing vegetables with liked and familiar foods and flavors. Canteen managers were provided with advice and support on how the vegetable content of their most popular hot meals could be increased.
- Changes to the online menu structure/choice architecture:
- Changes to the default: A recent menu analysis showed that 60% of sandwiches did not contain vegetables, with many having an option to additionally add (‘opt-in’) salad vegetables [11]. Based on the prospect theory, the strategy of having a salad vegetable on sandwiches as a default setting was developed. All protein-based (e.g., cheese/ham/turkey/chicken) sandwiches were served with a salad vegetable by default on the online menu, with the option for parents/students to opt-out.
- A brochure with additional suggestions to increase vegetable offerings. Canteen managers were provided with a 12-page brochure containing information and suggestions to increase the vegetable content of their menu. Suggestions were based on the results of the menu analysis of vegetable offerings on canteen menus [11] and included, among others, “Adding veggies to dishes children already love” (e.g., pizza, hot meal, sandwiches and salads), new vegetable items (snacks, meal deals) and promotion suggestions (focus on fun and taste testing with students to select better recipes). This brochure aligned with the CAMPOV model [20] by focusing on the importance of sensory acceptance and fun, and not focusing on the health benefits of increased vegetable consumption.
2.3. Procedure
2.4. Measures
- Menus of participating schools were assessed by a trained dietitian (S.D.) with over 5 years of experience in working with school canteens and reviewing school canteen menus according to the NSW Health and Department of Education guidelines [9]. Vegetable content (in g) was determined for each item on the online menu using information about ingredients, recipes and brands from the canteen manager.
- De-identified online sales data were provided by the online provider. Lunch orders in the categories ‘special events’ and ‘birthday buckets’ were excluded from the analysis as they related to group orders and not individual student orders. Brown-paper-bag orders (i.e., manually written orders typically submitted in a brown paper bag over-the-counter, rather than online orders) and over-the counter-sales (i.e., students buying foods at the counter at recess or after lunch) of any vegetable-containing items were recorded daily on a paper checklist by canteen managers.
- Vegetables sold (in grams) were calculated by multiplying the number of vegetable-containing items sold each day in the canteen by the vegetable content (in grams) of those items. Daily vegetable sales were converted to weekly sales by summation of daily totals.
- Vegetable sales data in subcategories of a typical school canteen menu structure [11] were analyzed using the procedures described above to determine whether the intervention affected specific subcategories of foods more than others.
- Canteen revenue: to determine that the intervention did not adversely (negatively) affect canteen revenue, total online canteen revenue data (in Australian dollars) were analyzed.
- Vegetable waste: this study assumed that vegetable sales are a good approximation of vegetable intake. To verify this assumption, student vegetable waste was collected from school grounds from a random sample of 4 participating schools (2 intervention and 2 control schools; one medium/high and one low SES school in each arm). Thus, this study considers plate waste and does not consider non-served foods as a source of waste [31]. Vegetable waste was measured over two representative days mid-baseline and the mid-intervention period. Dedicated bins and waste bags were provided during test days. Waste was collected by canteen managers and handed to research staff. On the same day, waste was sorted for vegetable items and weighed, using a systematic methodology based on procedures described by Boschini et al. [31]. Total waste (food and packaging) (A&D Personal Precision Scale, UC-321) and vegetable waste (Mettler Toledo Precision Balance, ME4002) were weighed and recorded.
- Acceptability of the intervention strategies and implementation of the multi-strategy intervention itself was evaluated through an online quantitative survey that intervention canteen managers completed after the intervention (Supplementary Materials). They responded to their level of agreement using 5-point Likert scales on five aspects of each of the intervention strategies: ease of implementation, if children responded positively to the strategy, if it was time-consuming or labor-intensive, if it was wasteful, and sustainability for the future. They also rated level of agreement to perceived factors influencing implementation based on the validated “Theoretical Domains Framework Questionnaire for Implementation (TDF)” [32] and the “Measurement Instrument for Determinants of Innovations (MIDI)” [33]. This included a total of 27 perceived individual (determinants including knowledge, self-efficacy, motivation and attitude) and environmental (determinants including the need for support, innovation and organizational support) factors (modified from [34]) (Supplementary Table S1). This was followed up with a short interview to gather qualitative information about their responses.
2.5. Statistical Analysis
3. Results
3.1. Participants
3.2. Intervention Implementation
3.3. Intervention Fidelity
3.4. Primary Outcome Measure: Vegetable Sales
3.5. Secondary Outcome Measures
3.5.1. Vegetable Sales in Subcategories
3.5.2. Sales Revenue
3.5.3. Vegetable Waste
3.5.4. Acceptability of the Intervention
4. Discussion
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Characteristics | Intervention Schools (n = 8) | Control Schools (n = 8) |
---|---|---|
Socio-economic status (n) 1 | ||
Low | 3 | 2 |
Medium | 3 | 3 |
High | 2 | 3 |
School sector (n) | ||
Government | 5 | 6 |
Non-government | 3 | 2 |
Students enrolled at school at baseline (n) 2 | 504 ± 259 | 562 ± 503 |
Canteen regular operating days/week | 5 ± 0 | 5 ± 0 |
Number of weekly lunch orders (at baseline) | 396 ± 191 | 505 ± 337 |
Days/week school closed during baseline period | 0.5 ± 0.2 | 0.4 ± 0.2 |
Days/week school closed during follow-up period | 0.1 ± 0.2 | 0.1 ± 0.1 |
Variable | Baseline, Mean (95% CI) | Follow-Up, Mean (95% CI) | Intervention Versus Control | |||
---|---|---|---|---|---|---|
Intervention (n = 8 Schools) | Control (n = 8 Schools) | Intervention (n = 8 Schools) | Control (n = 8 Schools) | Group-by-Time Differential Effect (95% CI) 1 | p Value 1 | |
Primary outcome | ||||||
Overall vegetable sales (in g/week) | 3630 (2757, 4503) | 4775 (3865, 5685) | 6418 (5872, 6964) | 4856 (4253, 5458) | 2707 (1276, 4137) | <0.001 |
Secondary outcomes | ||||||
Vegetable sales (in g/week) in subcategories | ||||||
Burgers | 375 (293, 458) | 636 (551, 722) | 641 (590, 692) | 570 (513, 626) | 332 (198, 467) | <0.001 |
Pasta/rice dishes | 1650 (1242, 2058) | 1558 (1133, 1983) | 2206 (1951, 2461) | 1726 (1445, 2008) | 388 (−280, 1056) | 0.25 |
Hot foods | 769 (532, 1005) | 1360 (1124, 1596) | 1722 (1577, 1869) | 914 (769, 1059) | 1399 (1008, 1790) | <0.001 |
Sandwiches, wraps, rolls | 346 (231, 462) | 480 (363, 595) | 669 (596, 738) | 624 (553, 696) | 176 (−16, 367) | 0.07 |
Snacks | 241 (34, 448) | 339 (132, 546) | 834 (707, 960) | 388 (261, 514) | 544 (201, 886) | 0.002 |
Sales revenue (in AUD/week) | 1546 (1352, 1739) | 2016 (1814, 2219) | 1701 (1579, 1822) | 1783 (1649, 1916) | 387 (70, 705) | 0.02 |
Variable | Baseline, Mean (95% CI) | Follow-Up, Mean (95% CI) | Intervention Versus Control | |||
---|---|---|---|---|---|---|
Intervention (n = 2 Schools) | Control (n = 2 Schools) | Intervention (n = 2 Schools) | Control (n = 2 Schools) | Group-by-Time Differential Effect (95% CI) 1 | p Value 1 | |
Total waste (kg/day) | 5.4 (0.9, 9.9) | 3.6 (−0.8, 8.1) | 7.1 (2.6, 11.6) | 2.4 (−2.1, 6.9) | 3.0 (−4.2, 10.2) | 0.38 |
Vegetable waste (g/day) | 107 (−29, 243) | −23 (−160, 112) | 182 (46, 318) | 49 (−87, 185) | 2 (−216, 220) | 0.98 |
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Poelman, A.A.M.; Djakovic, S.; Heffernan, J.E.; Cochet-Broch, M.; Golley, R.K.; Cox, D.N.; Beelen, J. Effectiveness of a Multi-Strategy Behavioral Intervention to Increase Vegetable Sales in Primary School Canteens: A Randomized Controlled Trial. Nutrients 2022, 14, 4218. https://doi.org/10.3390/nu14194218
Poelman AAM, Djakovic S, Heffernan JE, Cochet-Broch M, Golley RK, Cox DN, Beelen J. Effectiveness of a Multi-Strategy Behavioral Intervention to Increase Vegetable Sales in Primary School Canteens: A Randomized Controlled Trial. Nutrients. 2022; 14(19):4218. https://doi.org/10.3390/nu14194218
Chicago/Turabian StylePoelman, Astrid A. M., Shadia Djakovic, Jessica E. Heffernan, Maeva Cochet-Broch, Rebecca K. Golley, David N. Cox, and Janne Beelen. 2022. "Effectiveness of a Multi-Strategy Behavioral Intervention to Increase Vegetable Sales in Primary School Canteens: A Randomized Controlled Trial" Nutrients 14, no. 19: 4218. https://doi.org/10.3390/nu14194218