The 2020–2025 US Dietary Guidelines for Americans (DGAs) recommend following a healthy dietary pattern at every life stage [1]. USDA Food and Nutrition Service’s (FNS) Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) supports pregnant and postpartum women, infants, and children age 1–4 y who are low-income and at risk of poor nutrition [2]. WIC provides supplemental foods (“food packages”), nutrition education including breastfeeding support, and referrals to health and social services. WIC food packages are designed to supplement participants’ diets with specific nutrients and food groups and to contribute to an overall healthy dietary pattern. In 2005, the Institute of Medicine recommended that WIC food packages align with the 2005 DGAs and infant-feeding practice guidelines of the American Academy of Pediatrics [3]. An interim rule allowed for USDA to move forward with changes to the WIC packages, and they were implemented by October 2009. These changes, which included more whole fruits and vegetables, whole grains, and lower-fat milk, were the first comprehensive revisions to the WIC food packages since the nutrition program began in the early to mid-1970s [4].

Several studies on dietary intakes in the pediatric population and among WIC recipients have reported a positive association between WIC participation and improved dietary intakes [5–13]. However, studies have not evaluated trends in dietary intake among children who participate in WIC compared with children who are eligible but do not participate. Therefore, using 2005–2018 data, the objective of this study was to examine trends over time in the consumption of fruits, vegetables, whole grains, and low-fat milk and other dietary components among 1- to 4-y-old children who were WIC recipients, income-eligible nonrecipients, and those not eligible for WIC.

Data from seven 2-y cycles (2005–2006 through 2017–2018) of the cross-sectional National Health and Nutrition Examination Survey (NHANES) were used for these analyses. NHANES is a complex, stratified, multistage probability sample of the US civilian, noninstitutionalized population administered by the National Center for Health Statistics (NCHS). The survey combines an in-home interview and a standardized physical examination, including a dietary interview, at a mobile examination center (MEC). Details of the NHANES study design, implementation, datasets, analytic considerations, and other documentation are published or available on the Web [14, 15]. The NHANES protocol was approved by the NCHS Ethics Review Board. For children and adolescents <18 y, written parental consent was obtained. The sample design included oversampling to obtain reliable estimates of health and nutritional measures for population subgroups. During 2005–2018, various subgroups were oversampled, including non-Hispanic Black, Mexican American, and low-income White persons, and persons of other races and ethnicities. For young children (age 1–5 y), the NHANES examination response rates ranged from 86.9% to 55.2% from 2005–2006 to 2017–2018 [16].

Two 24-h dietary recall interviews were attempted for each survey participant; the first recall was conducted in person at the MEC, and the second was conducted by telephone 3–10 d later [14, 15, 17, 18]. Data from day 1 24-h dietary recall interview were used for this study. Trained interviewers, using the USDA’s data collection instrument, automated multiple pass method (AMPM) with standardized probes, collected the type and quantity of foods and beverages consumed during the previous 24 h [14]. Proxies reported dietary intakes for children 5 y of age or younger. Only records deemed reliable were used in the current analysis. The dietary data quality control criteria and methods are described in detail elsewhere [17].

The analysis sample included 1- to 4-y-old children with reliable dietary recalls (n = 5922) from the 2005–2006 through 2017–2018 NHANES cycles. Based on proxy reports, participants who were consuming breastmilk (n = 155) or were missing information on WIC participation status (n = 199) were excluded, resulting in a final analytic sample of 5568 children (Supple-mental Figure 1).

More than 30% of US children 1–4 y of age were WIC recipients (30.3%) and another 24% of the children were WIC eligible but did not participate in the program during the study period from 2005 through 2018 (Table 1). During this time, overall participation in the WIC program was similar for boys and girls, decreased with age, and varied by race and Hispanic origin. Mexican American (59.2%) children were more likely to be WIC recipients than non-Hispanic Black (45.0%) and non-Hispanic White (16.0%) children and non-Hispanic Black children were more likely than non-Hispanic White children to be WIC recipients. Similar patterns of WIC participation were seen for each 2-y cycle of the study period (Supplemental Table 1).

Figures 1–4 show the 2-y trends in the percentage of children (proxies) reporting intake, on a given day, of the examined food groups, and the amount consumed, by WIC participation status from 2005–2006 to 2017–2018, adjusted for age, sex, and race and Hispanic origin. Unadjusted trends are provided in Supplemental Tables 2 and 3.

Results from NHANES show that on a given day, from 2005–2006 to 2017–2018, WIC recipients consumed an increased percentage of total fruit as whole fruit and an increased percentage of milk as LFNF milk, changes not observed among WIC income-eligible nonrecipients. The increase in the mean percentage of fruit consumed as whole fruit could be because of a reduction in total fruit (whole fruit and 100% fruit juice) consumption, an increase in whole fruit consumption, or a combination of both. No changes, however, were seen in the percentage of children consuming, on a given day, any fruits or vegetables or the total amounts of whole fruits and vegetables consumed by both WIC recipients and income-eligible nonrecipients. The percentage of WIC recipients who consumed whole grains did not change from 2005 through 2012 but declined from 2013 through 2018, whereas among WIC income-eligible nonrecipients, the amount of whole grain consumption increased from 2005 through 2018. No changes were found in the percentage of children consuming added sugars, but the amount of added sugars and percentage of energy from added sugars significantly declined between 2005 and 2018 for all children 1–4 y of age.

Although studies have not evaluated trends in dietary intake among children who participated in WIC compared with children who are eligible but did not participate, several others have looked at changes in dietary patterns among WIC participants before and after the 2009 food package change [8, 13, 29–31]. A 2014 systematic review of literature [8] on the impact of the 2009 WIC food package change concluded that the revised food package was associated with improved dietary intake. Similar to dietary patterns seen in our trends study, 1 study reported increases in the amount of fruit and low-fat dairy consumption among Hispanic and African-American WIC-enrolled mothers and children [29]. However, this study was conducted only 6 mo after the food package change in 2009. Another study of the New York State WIC program evaluated WIC-enrolled participants from 2008 to 201l and reported an increase in daily consumption of fruit, vegetables, and whole grains among 1- to 4-y-old children [31]. A recent study [13] using NHANES data found increased intake of fiber, whole grains, and legumes and decreased intake of starchy vegetables among WIC participants 2–4 y of age between 2005–2008 and 2011–2014 during which time there were revisions to the WIC food package. No significant changes were observed in dairy or fruit intake [13]. The study did not compare these changes to changes in consumption among children not participating in WIC. The current study shows trends in consumption among WIC recipients along with trends among nonrecipient counterparts including those income-eligible and ineligible. In addition to including a wider age range of 1- to 4-y-old children, the current analysis disaggregates WIC food package categories, such as milk and fruit categories to examine the percent of milk consumed as low-fat/nonfat and the percentage of fruit consumed as whole fruit. This analysis also presents both the mean intake and percentage of children consuming each food category. Finally, exploring a longer period until 2018 can reveal whether any immediate changes after the food package revision led to long-term changes.

There have been other periodic studies evaluating dietary patterns by WIC participation status [6, 7, 9]. A study using NHANES 2011–2016 examined dietary patterns by race and ethnicity for WIC recipients and income-eligible and ineligible nonrecipients [9] and reported that Hispanic WIC recipients consumed less added sugar than their higher income counterparts. Hispanic WIC recipients consumed more fiber than income-eligible and income-ineligible nonrecipients. No differences in dietary patterns were observed by WIC participation status for non-Hispanic White and Black children. Our study does not report trends in dietary patterns by race and Hispanic origin but did control for race and Hispanic origin in the trend models.

Improved health outcomes have been associated with the food package change. Several studies of WIC-enrolled children have reported a decline in obesity after the food package change [32–35]. Daepp et al. [32] reported that before the 2009 WIC food package change, the prevalence of obesity across states among 2- to 4-y-old WIC participants was increasing by 0.23 percentage points annually. After 2009, the trend was reversed. Changes in sociodemographic and other obesity risk factors did not account for the declining trend. However, the decline in obesity after 2009 among children receiving WIC benefits reported in these studies was not observed among US children in general [36]. One difference between these studies and ours is the age groups. We analyzed change among children 1–4 y of age, whereas other studies have included 2–4 y or birth to 4 y of age children.

Our study is not without limitations. Children 1–4 y of age are unable to report food and beverage consumption for themselves, additionally, because they may be in childcare, the person reporting intake may not be the person most familiar with intake. Also, dietary intake was measured as intake on a given day and does not necessarily reflect usual intake. Limitations associated with self-reported dietary data, such as misreporting, have been described [14, 37, 38]. Finally, data may have been underpowered to detect significant trends for some groups.

Despite these limitations, the strengths of the study include the use of a nationally representative sample, including the more recently available data. Also, 24-h dietary recall data in NHANES were collected evenly across days of the week and seasons of the year, to account for day-to-day variation and random errors, hence they are representative of mean population intake. Finally, dietary data in NHANES are collected using the USDA’s AMPM method, which has cues to prompt respondent memory while reducing the respondent burden to obtain accurate recalls [39].

In conclusion, Changes in dietary patterns for WIC recipients did not always mirror those among other US children of the same age. From 2005 to 2018, although the percentage of 1- to 4-y-old children who consumed any fruits or vegetables on a given day did not change, the amount of fruit consumed as a percentage of whole fruit increased among children receiving WIC benefits, but not among WIC income-eligible nonrecipients. In 2017–2018, >62% of fruit consumed by WIC recipients was whole fruit compared with ~53% for WIC-eligible nonrecipients and almost 74% of WIC-ineligible children, all above DGA’s guidelines that at least half of the recommended amount of fruit come from whole fruit [1]. The percentage of children who consumed LFNF milk and the quantity of these kinds of milk consumed also increased significantly among WIC recipients but not among eligible nonrecipients, in line with the DGA’s recommendation of replacing full-fat dairy with low or nonfat alternatives for this age group [1].