Estimating the Impact of WIC on Diet Quality at Age 60 Months among Children Who Participated in the WIC Infant and Toddler Feeding Practices Study-2.

Abstract

This study aims to provide causal-like estimates of the relationship between participation in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) and children's diet quality using the public-use five-year WIC Infant Toddler Feeding Practices Study-2 (ITFPS-2) data. The WIC ITFPS-2 data was collected from 2013-2019 and analyzed from 2022-2026. The analytic sample (n=1,825) included children whose caregivers completed the enrollment and first post-natal interviews, participated in the 60-month interview, and provided anthropometric data. The outcome of interest was the child's Healthy Eating Index 2020 (HEI-2020) score at 60 months of age. The treatment was not receiving WIC at ages 13, 24, 36, 48, and 60 months. The relationship between HEI-2020 at age 60 months and duration of WIC participation was estimated using inverse probability of treatment weighting of marginal structural models (MSM). Selection into participation was addressed by weighting children in the sample (n=1,781) by the inverse of their probability of no longer receiving WIC at each age conditional on prior participation and time-varying and invariant characteristics. HEI-2020 scores at age 60 months averaged 55.2 out of 100 points. Based on MSM results, if all children in the sample had stopped receiving WIC at younger ages their HEI-2020 scores would have been lower than if they had been continuously exposed to WIC through age 60 months. If benefits ended at ages 13, 24, 36, and 48 months, average HEI-2020 scores at age 60 months would have been 8.6%, 9.2%, 7.1%, and 7.3% lower, respectively (all P<0.001). The findings strengthen the evidence linking WIC to better diet quality. Poor diet quality has been associated with compromised micronutrient intake, risk of obesity, and adverse developmental outcomes. Although continuous exposure to WIC was associated with higher HEI-2020 scores, all scores indicated room for improvement.