How changes in menu quality associate with subsequent expenditure on (un)healthy foods and beverages in school cafeterias: A three-year longitudinal study.

Evidence of the association between the school food environment and children's and adolescents' diet is mostly cross-sectional, usually based on self-reported behavior, and often conducted in high-income countries. Also, relatively little is known about how variations in menu quality associate with the subsequent expenditure on food and beverages of the same- (vs. cross-) nutritional value. Based on a three-year longitudinal dataset comprised of 4,268,457 purchases made by 20,333 children and adolescents from 54 private schools in Brazil, we unobtrusively assess how changes in (un)healthy product availability associate with students' subsequent purchase behavior. Our results reveal that, on average, only 11.6% of the products offered in the school cafeterias were of high nutritional value (HNV). Critically, expenditure on HNV products increased following both the addition of one HNV product (β = 0.18; 95% CI = 0.128, 0.240) and, to a lesser extent, the subtraction of one low nutritional value (LNV) product from the menu (β = -0.03; 95% CI = -0.042, -0.016). Cross-nutritional value effects were stronger for beverages. The inclusion of one HNV beverage was associated not only with a subsequent increase in expenditure on HNV beverages (β = 0.19; 95% CI = 0.115, 0.264), but also with a decrease in expenditure on LNV beverages (β = -0.18; 95% CI = -0.352, -0.010).Although only a small percentage of foods and beverages consumed in private school cafeterias in Brazil are of high nutritional value, improvements to menu quality have the potential to increase the consumption of healthier products and decrease the consumption of unhealthy ones.