Making every bite count: best practices for introducing foods during the complementary feeding period

See corresponding article on page 111.

The complementary feeding (CF) period, from ∼6 through 24 mo, is a developmental interval during which young children learn about flavors, food, and eating. Lifetime habits begin to form during this period. Early experiences with foods and eating, including social aspects learned via caregiver eating and feeding practices, form the foundation for long-term food acceptance. Thus, caregiver decisions about which foods are offered to infants and toddlers are important both for meeting children's current nutrient needs and for fostering positive early experiences with a variety of foods and food textures (1).

Global dietary guidelines for infants and toddlers place emphasis on the introduction of a variety of nutrient-dense foods during the CF period (2). Recommendations also include explicit advice that infants should be introduced to highly allergenic foods and to animal source foods rich in iron and zinc ∼6 mo of age, as this time (2, 3). This is particularly important for the breastfed infant because early iron stores are depleted, content in breast milk declines, and dependence on complementary foods increases to meet needs for both iron and zinc, underscoring the advantage of including iron- and zinc-rich foods early in the complementary feeding period (4). Because CF provides a foundation for healthy eating patterns in life, it is essential that families provide a diverse dietary intake while targeting the specific needs of their child.

Although clear evidence is limited regarding how the order of food group introduction relates to later food acceptance and dietary diversity, dietary recommendations for infants and toddlers include consumption of foods from all food groups (5, 6). Despite these guidelines, the WHO has estimated that only 29% of infants aged 6–23 mo have adequate dietary diversity (7). Vegetables tend to be underconsumed by toddlers (12–24 mo), and meat/protein foods are far less often consumed by infants (6–12 mo), despite the recommendation to offer these foods early in the CF period (8–11).

Many studies focusing on building food acceptance during the CF period have concentrated on increasing acceptance of fruit and vegetables (with an eye toward obesity prevention), whereas far fewer have focused on grains and/or meat (12, 13). Evidence is strongest for the strategy of repeated exposure—the continued offering of foods when they are first rejected—for reliably building food preference and consumption (12). Most studies have demonstrated that repeated exposure is effective to increase acceptance of both fruit and vegetables in the short term, although fewer have collected longitudinal data to determine whether effects are sustained beyond infancy. In addition, a few studies have employed repeated exposure in examining acceptance of animal source foods and grains and have reported similar effects to those of studies focusing on fruit and vegetables (14, 15).

In this issue of the American Journal of Clinical Nutrition, Rapson and colleagues (16) report the findings of a “starting complementary feeding with vegetables-only” randomized controlled trial targeting caregivers of 4- to 6-mo-old infants with the aim of improving vegetable acceptance in childhood. During a 4-wk intervention at the outset of offering solid foods, caregivers were provided either vegetables only or a vegetable and fruit mix to offer to their infant. Intake and rate of acceptance of target vegetables (broccoli and spinach) were measured at 9 mo of age, and indicators of iron status (hemoglobin and ferritin) were measured at entry into the protocol and at 9 mo of age. Caregivers were advised of the importance of offering iron-rich foods, although none were provided. As noted in previous studies, an effect of repeatedly offering the target foods resulted in increased consumption (albeit modestly so—about 1 tablespoon). No association was reported between indicators of iron status and treatment group, and most (92%) infants were iron sufficient at 9 mo of age with decreases in serum ferritin but stable levels of hemoglobin.

The results of this study again underscore that repeated exposure is effective and that early introduction facilitates food acceptance. That vegetables should be included among first foods offered during the CF period aligns with global guidelines for this feeding interval. However, the “vegetables-first” nature of the intervention, without an emphasis on iron-rich solids being offered concurrently, may direct caregivers’ focus away from important nutrient sources to maintain adequate iron and zinc stores for growth and neurodevelopment. The planned follow-up data to be obtained at 12, 24, and 36 mo of age, hopefully with adequate retention and assessment of nutrient status, will be particularly important to fully understand the larger implications of a vegetables-first approach because 1) the current study endpoint was 9 mo of age, when iron deficiency often begins to manifest; 2) only ∼50% of caregivers had introduced meat at 6 mo, although almost all had introduced meat by 9 mo; and 3) there was no indication of the adequacy of iron- and zinc-rich foods consumed over the course of the study.

The larger picture of dietary adequacy for young children emphasizes that early exposure to variety—from all food groups—is important. Although single-food (group) interventions work well to establish proof of concept for acceptance of those foods, they challenge the more comprehensive nature of the need for balance to support children's overall growth, health, and development. Early exposure to dietary variety, including micronutrient-rich foods rather than a focus on one food group only, aligns with current concepts related to dietary patterns. Maintaining vegetable exposure in the early food experiences alongside other needed foods and nutrients has been associated with improved dietary variety in early childhood, particularly in infants who have been formula fed (17).

Rapson and colleagues’ work (16) makes a contribution to the research gap related to CF practices, particularly for the 6- to 12-mo age interval. Additional research distinguishing the needs of the exclusively breastfed infant from infants who consume formula is of critical importance as their micronutrient needs differ and the prevalence of the exclusively breastfed infant is rising (18, 19). Maintaining focus on diet diversity and inclusion of all food groups to ensure nutrient adequacy, caregiver decisions about which foods to offer, and building dietary habits for a lifetime continue to be a critical goal for infant health and nutrition.

Notes

SLJ has funding and received honoraria for presentations from the Hass Avocado Board and the National Cattleman's Beef Association; SPG is supported by NIDDK grant T32-DK07658; NFK is supported by UG1 HD076474-07, R01 DK126710-01, and R01 DK113957-02. These funding sources had no role in the preparation of the manuscript. NFK is an Associate Editor of the American Journal of Clinical Nutrition and had no role in the editorial handling of this manuscript.