To our knowledge, this is the first study to assess the baseline environmental impacts of the US NSLP. Previous research has explored the environmental impacts of school lunches in Europe, the average American diet, and the Dietary Guidelines for Americans.11,12,13,14,15,16,17,18,19,20,21,23,24. Differences in meal composition and methods for estimating impact can make comparisons across problematic studies, however, the composition of low and high impact diets and contribution to impacts from food groups generally aligned across studies.
Previous research has shown that low-impact diets have less animal products and more whole grains and legumes1,20,25. Rose et al. (2019) found that American diets with low greenhouse gas emissions (GHGE) have about twice the whole grain, legume, and nuts and seed content and less than half the animal protein content of high GHGE diets. Low impact school lunches had similar differences with ~ 20% more whole grains, nearly 20 times more nuts and seeds, and four times less animal protein than high impact lunches. Differences in magnitudes across the studies can be explained by differences in the compositions of school lunch and the average American diet, modeling procedures, and coverage of impact categories.
Meat and dairy have been repeatedly identified as major contributors to dietary environmental impacts across impact categories, while fruits and vegetables have been linked to water use.19,20,21,26. The percent contribution of meat to lunch water consumption (28%) and GWP (67%) was similar to its contribution to impacts of the American diet (35% Blue Water and 55% GHGE).21. In school lunch, poultry stood out as a major contributor to water consumption (19%) because it is commonly served; poultry accounted for over half of all meat served in schools. This differed with poultry’s contribution to water scarcity in the average American diet (5%), partially because beef is consumed in relatively greater quantities in the American diet. Fruits and vegetables accounted for 40% of the water consumption of lunches. While this is a large proportion of impact, fruits and vegetables account for about 36% of lunch mass.
The US has ambitious goals for environmental protection which will require concerted efforts across government policy and programs and could include changes to nutrition standards for federal food assistance programs.27. Our estimates can be used to evaluate changes to standards and benchmark progress in reaching national environmental goals. Additionally, this work starts to identify potential areas for policy changes based on the composition of low and high-impact lunches, as well as the food groups which had the greatest contribution to impacts.
Any policy recommendations, however, must be considered in light of other components of dietary sustainability including food costs and access, school infrastructure, nutrition quality, and children’s previous exposure to certain types of foods and acceptance of foods. While access to low-impact foods could be an obstacle for certain districts, major food distributors and food service providers have made commitments to provide more environmentally sustainable menu options including more plant-based foods, which could make it easier for schools to begin serving more. sustainable menus28,29. As for student acceptance, food and nutrition education interventions can be paired with menu changes for effective implementation30,31. Particularly, education related to food systems and the environmental impacts of agricultural and food waste have been successful32,33.
Our work affirms the results of numerous studies which highlight beef as a major contributor to the environmental impacts of diets2,21,25,34. We found that, on average, high-impact lunches contained about 1 oz. eq. more beef than low-impact lunches. In the context of the NSLP meal pattern requirements, this is the minimum daily serving of a meat or meat alternative for kindergarten through 8th grade lunches. Beef was also the single greatest contributor to GWP, land use, and marine eutrophication. Our findings suggest that to reduce the environmental impacts of school lunch, policy should consider limiting servings of beef.
Tens of thousands of lunches served during the 2014–2015 school year had low environmental impacts across impact categories, providing a wide array of examples to support recommendations. The composition of these lunches was generally consistent with previous work identifying low-impact diets1,2. One characteristic of these lunches was greater portions of whole grains, which partially compensated for lower servings of beef and pork. Federal policy could encourage the service of low-impact lunches by increasing the requirements for whole grains. Whole grains are a nutritious, low-cost, diverse, and versatile food group that might offer solutions to the tradeoffs commonly confronted when proposing the consumption of sustainable diets.35.36. We observed no difference in refined grain content of low and high-impact lunches; Therefore, an increase in the whole grain requirement would not be associated with changes to refined grains.
Low impact lunches also contained greater servings of seafood, and nuts and seeds. Within these categories, there is considerable variability in impacts across foods26. To recommend serving requirements for these food groups, school districts would need further guidance specifying food types and production practices. In general, the impacts of nuts and seeds are relatively low compared to animal-based protein, however tree nuts such as almonds and pistachios require 3 to 6 times more water than animal proteins.26,37. Based on their environmental impacts, peanuts, the most served nut in school lunch, and less commonly served seeds such as sunflower, sesame, or pumpkin seeds could be good alternatives to tree nuts.
If federal policy sets seafood requirements for lunch, fish should be sourced from well-managed, wild populations with fishing methods, which reduce by-catch and habitat destruction.38. Fish produced in low-intensity, non-recirculating aquaculture could also be good options because they are associated with lower GWP than trawling fisheries.38. However, they have relatively high eutrophication potential and can threaten wild species genetics38.39. In New England, school districts are sourcing Acadian Redfish (Sebastes fasciatus); Because this species is sustainably managed and less commercially popular, it is also inexpensive40.
If limits on the servings of beef are put in place, grains, nuts and seeds, and seafood might be strong potential replacements given their nutritional composition and potential to provide health benefits.35,41,42. However, cost differentials might make this prohibitive in some circumstances, and new recipes incorporating these foods into entrées will be necessary. Additionally, it is important that any changes to standards be well received by students and school food administrators. Studies are needed to inform implementation (ie, kid-friendly recipes, logistics for cooking, and sourcing) and limit unintended consequences such as increased food waste. Changes to school meals standards and practices should be incremental, flexible, and will take time.
Dairy was found in greater quantities in the low-impact lunches even though it was one of the leading contributors to all impact categories except water consumption. This was because low-impact lunches on average contained more cheese. Cheese is classified as a meat or meat alternative for school meal planning43. It is a common vegetarian option, which is used as a substitute for beef or meat. The lowest impact lunches contained more cheese because cheese displaced meat. Cheese generally has greater environmental impacts than plant-based proteins or other meat alternatives. Additionally, because of potential issues with sodium and saturated fat content, increasing cheese in school lunch might not lead to the dual benefits of improved nutritional and environmental outcomes.26. Our results are therefore inconclusive regarding changes to recommendations for dairy.
The composition of the lowest and highest impact lunches were inconsistent across impact categories for fruit. As seen in our work and previous research, fruit is a major contributor to water consumption19,21,44. Therefore, the lunches with the greatest water consumption had more servings of fruit than the lowest impact lunches in this category. This trend was not consistent across other impact categories. For all other impact categories, the lowest impact lunches had greater servings of fruit. This inconsistency presents a tradeoff between water consumption and the other impact categories, however on average the difference in the amount of fruit between the highest and lowest impact lunches was trivial (~ 0.1 cup eq.). As with dairy, our results do not provide a conclusive recommendation for changes to fruit requirements.
The NSLP is deeply tied to domestic agricultural markets through the Buy American Provision and United States Department of Agriculture (USDA) Foods program45,46. An important function of the NSLP is to stabilize commodity prices by creating demand for goods. Given the relationship between the NSLP and US agriculture, changing the school meals standards presents a unique opportunity to align the NSLP meal pattern requirements with USDA conservation efforts.
By shifting the NSLP recommendations, there is potential for school meals to create markets for products produced using conservation practices. Alley cropping and conservation crop rotations are two practices supported by USDA Environmental Quality Incentives Programs. These practices protect the environment by improving soil health and biodiversity, and improve farmers’ ability to respond to climate change. Integrating these practices can produce small grains, nuts, and seeds. If the NSLP standards required greater servings of these food groups, farmers could take advantage of the stable market prices provided by school districts and schools could potentially integrate products that were previously cost-prohibitive (ie, barley, oats, sunflower seeds). Linking recommendations to increase grains, nuts, and seeds in school lunch with these types of conservation practices could produce win-win-win cases for nutrition, environment, and economic outcomes. At the same time, political will be needed to make these connections a reality. Unfortunately, as has been seen with slow progress in changing school meal standards and incorporating sustainability into the dietary guidelines, the outlook for this might not be strong.
This study used a nationally representative sample of foods served in the NSLP and consistent and transparent LCA data, however, there were limitations in the data and methods. Due to data availability, we used water consumption as opposed to a water scarcity metric, the latter of which measures water use in relation to water availability. Estimates of water scarcity for the US consumed foods are now available and could be integrated into future studies21. Most studies on the impacts of diets, including this work, end assessment at the farm or processor gate20. Although agriculture is the predominate driver of impacts, a full picture of impacts beyond the farm gate could be useful26.
It should be noted that this study did not consider the proportion of beef in school lunches from dairy systems due to data limitations. Environmental impacts of beef from dairy production can be three times less than beef from beef breed animals26. In 2018, 21% of beef consumed in the US came from dairy systems47. The NSLP receives surplus foods and might rely more on dairy beef than the national market. This would lower our estimated impact of lunches and impacts from meat and beef.