How Do School Salad Bars Impact Elementary School Students' Dietary Quality and Energy Intake at Lunch? A Randomized Controlled Plate Waste Investigation

Abstract

Background: Children's dietary quality is suboptimal, increasing the risk of numerous chronic illnesses. Salad bars (SBs) have potential to enhance children's nutritional intake within the National School Lunch Program (NSLP); yet, empirical support is lacking. To address this gap, we evaluated the impact of school salad bars on dietary quality and energy intake at lunch. Methods: Seven matched elementary school pairs were randomly selected. All schools served pre-portioned fruit and vegetables (F&V) at baseline. Within each pair, one school received an SB. Digital imagery plate waste methods were applied at baseline and 4-6 weeks post salad bar installation to determine intake (20% increments for food, ounces for beverages). Dietary quality (Healthy Eating Index (HEI-2015)) and energy intake (kcal) were evaluated in NDSR. Multilevel modeling evaluated group (SB vs. control) and time (baseline vs. post) differences and group-by-time interactions for: (1) HEI-2015 (total and component scores) and (2) kcal intake (overall, F&V, non-F&V, and beverage kcals). Results: Data from 5674 trays are reported. Significant group-by-time interactions were observed for HEI-2015 total scores and Greens and Beans, Total Fruit, Whole Fruit, Refined Grains, and Added Sugar component scores (p < 0.0001), supporting improved dietary quality in SB schools. SB HEI-2015 scores were 60.1 ± 9.8 at post (+5.3 from baseline; p < 0.0001) compared with 57.2 ± 9.5 in controls (+1.0 from baseline; p = 0.065). Total energy intake significantly increased in SB schools (376 ± 151 kcal (baseline) → 434 ± 176 kcal (post)), driven by F&V energy (+59 kcal), with no change for controls. Discussion: Within the NSLP, SBs improved dietary quality and increased energy intake due to increased F&V intake without replacing other foods. Results can inform school nutrition policies designed to reduce chronic illness risk.

Keywords: Healthy Eating Index; National School Lunch Program; chronic illness prevention; dietary quality; salad bars.

Figure 1

Flow chart of student tray exclusions to yield the final analysis sample. Note: trays that were double rated for quality control were retained until near the final step to maximize the analysis sample; thus, exclusions include double rated trays.