EXAMINING INFANT AND MATERNAL DIET IN THE FIRST TWO YEARS

Abstract

The diets of infants and mothers play an important role in overall health. Newborns consume a liquid diet composed of human milk, infant formula, or both, and eventually are introduced to complementary foods and beverages as a bridge towards the table food diet of toddlerhood, childhood, and adulthood. In this context, mothers are typically the conduit to the liquid, complementary, and table food diets of their children and as such, maternal diet holds an important role in understanding the diets of young children. While there is an abundance of research focused on human milk fed mother-infant dyads, limited research has focused on their formula feeding counterparts. The objectives of this dissertation were two-fold. First, we used data from the National Health and Nutrition Examination Survey (NHANES; 2007-2008 through 2017-2018), a cross-sectional, national study of United States citizens, to determine the types of milk (e.g., human milk, infant formula, and other milk) fed to infants and toddlers younger than two years in the United States and assess intake trends over time (e.g., 2007-2012 to 2013-2018). Second, we describe the a posteriori diet patterns of formula-fed infants and their mothers in the first two years. These mother-infant dyads participated in a randomized controlled trial with repeated measures of diet intake over time, setting the stage for evaluating the effects of randomization to two different types of infant formulas on the patterns of foods and beverages ingested by infants and mothers over time. The foods fed during infancy may persist into childhood, and specific to mothers, the foods of the maternal diet may become part of their child’s diet. Infant and toddler (0 to 23.9 months of age) data from the NHANES (2007-2018; N=3,079) were used to address the first objective. From 2007-2012 to 2013-2018, the proportion of 0 to <3, 3 to <6 and 6 to <9-month-old infants fed infant formula as a sole source of nutrition declined by approximately 10% within each age group (all P-values <0.03). However, the proportion of 0 to <3 and 6 to <9-month-old infants fed partially hydrolyzed infant formula doubled from 2007-2012 to 2013-2018 (all P-values <0.02). In toddlers (>12 months old), cow milk was the predominant milk type in both 2007-2012 to 2013-2018. Taken together, the data suggest that the percentage of infants fed any human milk or partial hydrolysate formulas has increased, and in toddlers, unsweetened cow milk is the predominant milk type consumed. For the second and third objectives, monthly infant and maternal diet data from an infant formula randomized control trial (RCT) were used to identify diet patterns using principal component analysis. Four infant diet patterns were identified over the first 1.5 years: (1) “infant formula”; (2) “low-sugar cereal, not fried potatoes, grain mixed dishes, fruit, vegetables, meat mixed dishes, 100% fruit juice”; (3) “milk, pizza, water, high-sugar cereal & snack/meal bars”; and (4) “fried poultry, bakery products, fried potatoes, starchy vegetables”. Two clusters emerged for how infants transitioned through these diet patterns over time: in cluster A (n=55), most infants transitioned from the “infant formula” to the “low-sugar cereal, not fried potatoes, grain mixed dishes, fruit, vegetables, meat mixed dishes, 100% fruit juice” pattern starting at 6.5-7.5 months and remained in this pattern through 10.5-11.5 months; in cluster B (n=25), most infants transitioned from the “infant formula” to the “milk, pizza, water, high-sugar cereal & snack/meal bars” pattern starting at 8.5-9.5 months and remained in this pattern through 10.5-11.5 months. By 12.5 months most infants (60%) across both clusters were in the “milk, pizza, water high-sugar cereal & snack/meal bars” or “fried poultry, bakery products, fried potatoes, starchy vegetables” pattern. Four maternal diet patterns were identified over the first 1.5 years postpartum: (1) “sweetened drinks, grains, cured meats & poultry, sugars, poultry”; (2) “coffee & tea, fruit, sugar substitutes, yogurt, healthy fat produce, diet beverages, water”; (3) “dairy desserts, quick breads, milk & cow’s milk substitutes, pizza”; (4) “milk & cow’s milk substitutes, high-sugar cereal, low-sugar cereal, 100% juice”. There were no differences in the proportion of mothers in each diet pattern over time (Chi-square, X2=10.1, P=0.929). In summary, analyses of national data indicate that the percentage of infants fed any human milk and the percentage of infants fed partially hydrolyzed protein formula has increased. Analyses of the complementary diet from an RCT of formula-fed infants indicates that by the end of the first year of life, most infants have already been introduced to foods that are recommended to be limited (e.g., sweetened products, fried foods) and some of these same foods are seen in maternal diet patterns of the postpartum period. Since maternal diet may predict infant diet, and infant diet may persist into later life, nutritional guidance on healthy food choices and nutrient-dense diet patterns for mothers and infants should be a focus during the first two years.