Sustainable and acceptable school meals through optimization analysis: an intervention study

Abstract

Background: School meals hold considerable potential to shape children's diets and reduce food-related greenhouse gas emissions (GHGE)-in the short and long term. This study applied linear optimization to develop a GHGE-reduced, nutritionally adequate, and affordable school lunch menu. The effects on food waste, consumption and pupils' satisfaction with the meals were evaluated. Methods: A pre-post design was employed to assess the effects of implementing an optimized lunch menu on daily food waste, consumption, and pupils' school meal satisfaction in three schools (grades 0-9) from one Swedish municipality. A food list containing amounts, prices, nutrient content, and GHGE-values of all foods used for a previously served (baseline) four-week lunch menu was created. Using linear programming, this food list was optimized for minimum deviation and constrained to ensure nutritional adequacy and a reduced climate impact. The optimized food list was developed into a new (intervention) four-week lunch menu by a professional meal planner, following the baseline menu as closely as possible. The baseline and intervention menus were served for four weeks, respectively, with a two week break in between. Prepared, wasted and leftover food were weighed daily by the school kitchen staff during both periods. Interrupted time series analysis assessed mean and slope differences in daily food waste and consumption between the two periods. School lunch satisfaction was assessed with an online questionnaire at baseline and during the intervention. Results: Optimization resulted in a food list that was 40% lower in GHGE, met all nutrient recommendations for school meals, and cost 11% less compared to baseline. The intervention menu was served as planned, with only minor changes required (for practical reasons). Plate waste, serving waste, consumption and school lunch satisfaction did not differ significantly from baseline, in any of the schools. Conclusions: The findings demonstrate that school meals can successfully be improved regarding health and environmental sustainability using linear optimization, without negative effects on food waste, consumption or cost. This approach offers the necessary flexibility to tailor menus towards different priorities and could therefore be transferred to other types of meal services.

Successful Implementation of Climate-Friendly, Nutritious, and Acceptable School Meals in Practice: The OPTIMAT™ Intervention Study

“…The study employed a pre-post design using interrupted time series (ITS) analysis to investigate the effect of introducing an optimized lunch menu on daily food waste and consumption in schools [22]. Pupils in four primary schools followed their usual (baseline) menu plan during a period of four weeks and after a one-week mid-term break, the optimized four-week menu plan was served daily during the intervention period.…”

“…Three of the four schools were located in rural areas about 25 km from Uppsala city center, while one school was located in the outskirts of the city. The research team presented the project's idea of implementing more climate-friendly lunches in schools and findings from the previous intervention [22] in three large schools in a different municipality. We drew up written agreements with all four participating schools concerning tasks to be performed by the school and by the research team, respectively, and these were signed by the headmasters and the principal investigator (L.S.E.).…”

“…This database is not open to the public and access was paid for by the research team. As described previously [19,22,28], all calculations of nutritional adequacy were based on the nutrient content of the edible proportions of prepared (cooked, boiled, oven baked, etc.) foods, while the calculations for cost and CO 2 eq were done on the amount of raw food.…”

“…The baseline food list was optimized following a linear programming (LP) strategy described in detail elsewhere [19,22] and was implemented with the COIN-OR Branch and Cut Solver (CBC) algorithm, part of the Excel ® 2016 software add-in OpenSolver, V. 2.9.0 [29]. Briefly, LP aims to either minimize or maximize a linear objective function that is subjected to a set of linear constraints having to be met simultaneously.…”

“…It has also been used to mathematically design nutritious and environmentally sustainable school meals [19][20][21]. Our research group has developed and tested a pragmatic approach for combining linear optimization with planning and serving of a new school lunch menu [22]. In this first-ever intervention, no undesirable effects on food waste or consumption were observed.…”