Impact of a baby-led approach to complementary feeding on iron and zinc intake and status: A randomised controlled trial
Background: Baby-Led Weaning (BLW) is an approach to complementary feeding that is gaining popularity amongst parents worldwide. In this alternative approach to traditional spoon-feeding, infants feed themselves all of their food from the start of complementary feeding, which means that foods offered need to be finger foods that they can hold themselves. Although there are several proposed advantages of BLW, health professionals have expressed some concerns. Iron and zinc are a particular concern because commonly introduced ‘first foods’ that are easily picked up, such as fruits and vegetables, tend to be low in iron and zinc. No studies have yet investigated the impact of a baby-led approach to complementary feeding on biochemical iron and zinc status. Further to this, no studies have determined potentially modifiable ‘predictors’ of zinc status in toddlers from high-income countries. Objectives: The overall aim of the Baby-led Introduction to SolidS (BLISS) randomised controlled trial was to determine whether a modified version of BLW prevents young children from becoming overweight, without increasing their risk of iron deficiency, growth faltering, and choking. The aim of this thesis was to determine the impact of this version of BLW modified to prevent iron deficiency, on iron and zinc intakes and status, and to determine potentially modifiable ‘predictors’ of zinc status in toddlers. Methods: A total of 206 participants were randomised to Control or BLISS groups. Both groups received standard Well Child care from before birth. The BLISS group received eight additional visits (from before birth to 9 months) providing education and support on following the BLISS approach (i.e. BLW modified to increase iron intake). Weighed three-day diet records were used to assess the intake of key nutrients at 7 and 12 months, and a blood sample was collected using trace-element free techniques to determine biochemical iron and zinc status at 12 months. Multiple regression analysis was used for the outcomes of the randomised controlled trial following the principles of modified intention to treat. ‘Predictors’ of zinc status were determined by univariate, then stepwise linear bootstrap, and multivariable regression analysis. Results: There was no evidence of a difference in dietary iron and zinc intakes between the groups at 7 or 12 months (all p>0.42). However, there was a high prevalence of inadequate iron intakes (7 months: 74%, 12 months: 23-36%). There were no statistically significant differences in plasma ferritin (median: 29 μg/L Control, 27 μg/L BLISS; difference -2.6 μg/L; 95% CI -10.9, 5.8; p=0.55) or plasma zinc (mean: 9.6 μmol/L Control and BLISS; difference -0.09 μmol/L; 95% CI -0.67, 0.48; p=0.75) concentrations between the groups at 12 months. The majority (83%) of toddlers were iron sufficient, although a high proportion had low plasma zinc concentrations (63% Control, 57% BLISS). Red meat intake (p=0.028), infant formula intake (p=0.009), and food fussiness (p=0.021) were statistically significant ‘predictors’ of plasma zinc concentration at 12 months. Conclusions: These results suggest that a baby-led approach to complementary feeding does not appear to increase the risk of iron or zinc deficiency when parents are given advice to offer ‘high-iron’ foods at every meal. It is important to note, however, that this study assessed a modified version of BLW so no conclusions can be made about the risk of iron and zinc deficiency in infants following unmodified BLW. Red meat intake, infant formula intake, and food fussiness were all significant ‘predictors’ of zinc status at 12 months. Of particular interest is the association with food fussiness, and further research should investigate whether interventions to improve food fussiness could improve zinc status, or whether improvements in zinc status would improve food fussiness in this age group.
Advisor: Heath, Anne-Louise M; Taylor, Rachael W; Gibson, Rosalind S; Samman, Samir
Degree Name: Doctor of Philosophy
Degree Discipline: Human Nutrition
Publisher: University of Otago
Keywords: Baby-Led Weaning; complementary feeding; nutrient intake; iron deficiency; zinc deficiency; New Zealand; infants; toddlers; food fussiness
Research Type: Thesis