The New School Food Standards and Nutrition of School Children: Direct and Indirect Effect Analysis

Year: 2019

Research Center: Tufts University/University of Connecticut (UConn) RIDGE Program

Investigator: Valizadeh, Pourya and Shu Wen Ng

Institution: University of North Carolina, Chapel Hill

Project Contact:
Pourya Valizadeh
The University of North Carolina at Chapel Hill
Carolina Population Center
CB #8120 University Square
123 West Franklin Street
Chapel Hill, NC 27516-3997
Phone: 919-962-6188


Healthy dietary quality in childhood is essential for the proper physical and cognitive development of children as well as for preventing a variety of adverse health outcomes such as childhood obesity. To promote adequate nutrition among school children, particularly those from low-income households, federally subsidized school lunch and breakfast programs serve about 30 million lunches and 15 million breakfasts to students each school day. The Healthy, Hunger-Free Kids Act (HHFKA) of 2010 marked the most sweeping changes to the school nutritional standards in 15 years. The new rules officially went into effect in the 2012-13 school year for school lunches and the 2013-14 school year for breakfasts, resulting in the increased availability of whole grains, fruits, and vegetables, while decreasing sodium and saturated fats and allowing only fat-free/low-fat milk.

This study examined how the HHFKA-induced changes in school nutritional standards affected dietary quality (measured by the Healthy Eating Index 2010) of school children from different food acquisition sources (i.e., school versus away-from-school food sources). Specifically, the study estimated the overall, direct, and indirect effects of the HHFKA on dietary quality of school-age children. The overall effect analysis explored the impacts on the dietary quality of foods acquired from all food sources (i.e., both school and away from school). The direct effect analysis focused on the dietary quality of foods obtained from the school cafeteria. The indirect effect analysis investigated the impacts on the diet quality of foods acquired from the away-from-school food sources (e.g., home, restaurants, fast food establishments). This study also investigated the overall impact of the HHHKA on children’s daily calorie intake.

The main identification strategy focused on comparing the effects of consuming school food, rather than away-from-school food, on children’s dietary outcomes before and after the HHFKA implementation. To account for endogeneity of school food participation, the study used 2-day dietary intake data from four cycles (2009-2016) of the National Health and Nutrition Examination Survey (NHANES) and exploited within-child variations to control for fixed unobserved and observed confounders associated with school food consumption and dietary outcomes (e.g., food preferences, parental characteristics, school environment, income, age, gender).

The study sample was restricted to school-age children (4-19 years old) who had complete dietary intakes on both dietary intake days and reported attending a K-12 grade school during the school year. The full sample included n=7,341 children and N=14,682 observations. To conduct heterogeneity analysis by a child’s school grade, children were grouped into K-5 graders (n=3,534) and 6-12 graders (n=3,807). Further, children were classified as low-income if their household incomes were less than or equal to 185 percent of Federal poverty guidelines (n=4,250), and as high-income otherwise (n=3,091). The period from 2009 to 2012 was considered as the pre-HHFKA implementation period and from 2013 to 2016 as the post-HHFKA period.

Lastly, using the reported food acquisition sources in NHANES, the school food category was defined as all foods (including both subsidized school meals and competitive foods) acquired from the “cafeteria in a K-12 school.” At-home food primarily contained food items purchased at grocery stores. Food away from home and school (FAFHS) broadly included full-service restaurants, fast foods, and vending machine items.

This study documented a significant increase in the overall dietary quality of the average student from the pre- to the post-HHFKA implementation period. The direct effect analysis indicated a significant increase in the diet quality of children's intake of school food, particularly among older and higher-income children. The indirect effect analysis found a negative impact on the away-from-school dietary quality, largely driven by a subset of children consuming more than a third of their daily calories from school food. A more detailed analysis of the negative indirect effect found that this result was driven by consuming lower quality diets at home, and no significant impact was observed on the food-away-from-home-and-school (e.g., restaurants, fast foods) diet quality.

Together, the direct and indirect effect estimates suggested that, although school children shifted towards consuming lower quality diets away from school, the unintended negative consequences were not strong enough to eliminate gains in overall dietary quality brought by post-HHFKA school foods. In terms of the impacts on the daily calorie intake of children, there was evidence of a modest reduction in daily calorie intake in the post-HHFKA implementation period, primarily among older and higher-income children. Overall, this study’s findings implied that the HHFKA, despite its unintended negative indirect effects, led children to consume more-nutritious, less-energy-dense diets.