Abstract
Background: Infancy is a critical period for development, and nutrition practices during this time can have short- and long-term effects on health. While breast milk and formula feeding have been extensively studied, less attention has been given to the complementary feeding period, particularly emerging feeding methods such as the use of baby food pouches and baby-led weaning. There are concerns that these feeding methods may compromise nutritional adequacy, especially regarding iron. However, there is limited evidence to evaluate these concerns. Therefore, further research is needed to develop evidence-based recommendations for infant feeding practices during this crucial phase of growth and development.
Aim: The overall aim of this thesis was to investigate the relationship of frequent baby food pouch use and baby-led weaning with nutrient intake and iron status in New Zealand infants aged 7 to 9.9 months.
Methods: This thesis analysed data from the First Foods New Zealand (FFNZ) study, an observational study of 625 New Zealand infants aged 6.9 to 10.1 months. Nutrient intake was assessed using two 24-hour recalls, with breast milk intake measured in a subsample of 158 infant-mother pairs using the dose-to-mother stable isotope (deuterium oxide) method and predictive equations used to estimate intakes in the remaining sample. Iron status was measured using a non-fasting venepuncture blood sample. Questionnaires were administered to collect data including demographic and infant feeding measures. Feeding methods were defined based on parent self-report of infant feeding at “around 6 months of age” and “in the past month”: frequent baby food pouch use was defined as parents reporting that their infant consumed baby food from pouches 5 or more times per week, while full baby-led weaning was defined as parents reporting that the feeding approach used with their child was “mostly baby feeding themselves, some spoon feeding by an adult” or “baby feeding themselves”.
Chapter 4 aimed to describe baby food pouch use in New Zealand infants and identify the characteristics of frequent users. The results showed that while most infants (79%, 492/625) had used a pouch at some point, only 28% (n=174/625) were current frequent users, and an even smaller proportion were frequent users who consumed the contents through the nozzle regularly (5%, 30/625). Factors that positively predicted frequent pouch use included higher household deprivation level and the respondent being in full-time employment, while use of baby-led weaning and current breastfeeding inversely predicted frequent pouch use.
Chapter 5 aimed to describe the nutrient intake of New Zealand infants, with a focus on exploring the relationship between nutrient intake and frequent baby food pouch use, and between nutrient intake and baby-led weaning. The estimated usual intakes of New Zealand infants were adequate for most nutrients; however, the prevalence of infants at risk of inadequate iron intake was 58%. Frequent baby food pouch use was associated with significantly higher intakes of energy and total sugars, as well as several micronutrients including iron, zinc, iodine, calcium, vitamin B12, and vitamin C. However, this was largely attributable to the higher intakes of infant formula in frequent pouch users, with total sugars intake the only notable remaining difference in adjusted analyses (mean difference: 4.2 g/d [95% CI: 1.4 to 7.0]). Infants who followed full baby-led weaning had lower iron intakes than those following traditional spoon-feeding, although this association was attenuated when controlled for potential confounders (mean difference: -0.8 mg/d [95% CI: -1.2 to -0.3]).
Chapter 6 aimed to describe the iron status of New Zealand infants and examine potential feeding predictors of infant iron status, with a focus on frequent baby food pouch use and baby-led weaning. The prevalence of suboptimal iron status among New Zealand infants was 23%. After controlling for several potential confounding factors, including infant formula intake, neither feeding method predicted body iron concentrations or odds of being iron sufficient. The adjusted OR for iron sufficiency was 1.51 (95% CI: 0.67 to 3.41) for frequent pouch users compared to non-pouch users, and 0.91 (95% CI: 0.45 to 1.86) for infants following baby-led weaning compared to those following traditional spoon-feeding.
Conclusion: Contrary to prevailing concerns, this thesis provides evidence to suggest that the current implementation of baby food pouch use and baby-led weaning does not significantly compromise nutrient adequacy and iron status in this age group. However, further research is required to explore the potential effects on infant health of higher total sugars intake among frequent pouch users. Moreover, this thesis underscores the importance of continued attention to iron status in New Zealand infants during the complementary feeding period, regardless of the chosen feeding method. Furthermore, it highlights the need for a nuanced approach to assessing the impact of feeding methods on infant nutrition, taking into account other concurrent feeding behaviours, particularly the type of infant milk consumed. Overall, this thesis provides some reassurance to health professionals, policy makers, and whānau (families), that baby food pouch use and baby-led weaning, as currently practiced in New Zealand, are unlikely to have a negative impact on infant nutrition.