Effects of cow milk versus extensive protein hydrolysate formulas on infant cognitive development

Abstract

Little research has focused on infant developmental effects, other than growth, of formulas that differ substantially in the form of protein. To examine development of infants fed formulas differing in free amino acid content, we randomized 0.5-month-old infants (n = 79) to either a control group who fed only cow milk formula (CMF) during the first 8 months (CMF8), or to one of two experimental groups: one experimental group fed extensively protein hydrolyzed formula (EHF) for 1-3 months during first 4.5 months (EHF1-3) of life, and the other fed EHF for 8 months (EHF8). The Mullen Scales of Early Learning were administered monthly from 1.5 to 8.5 months to assess fine (FM) and gross (GM) motor control, receptive (RL) and expressive (EL) language, visual reception (VR), and an early learning composite (ELC). Across the 5.5-8.5-month time period, when compared to CMF8 infants, GM scores in EHF1-3 infants averaged 1.5 points higher (95 % CI 0.1, 3.0) and in EHF8 infants 2.2 points higher (95 % CI 0.3, 4.0). Similarly, VR scores averaged 1.9 points higher (95 % CI 0.1, 3.8) in EHF1-3 infants and 2.2 points higher (95 % CI -0.2, 4.5) in EHF8 infants. EHF8 infants' RL scores averaged 1.8 points lower (95 % CI 0.1, 3.6) than CMF8 infants. These data suggest that the form of protein in infant formula may impact cognitive development and that the higher free amino acid content in breast milk may be a contributing factor to the differential cognitive development between breastfed and CMF-fed infants.

Clinical trial registration: clinicaltrials.gov NCT00994747.

Keywords: Cognitive development; Cow milk formula; Extensive protein hydrolysate formula; Free amino acids.

Figure 1

Mean and SEM Mullen Scale scores by diet group (CMF8, EHF1-3, EHF8) and time point (5.5–8.5 months): gross motor (a), visual reception (b), receptive language (c), fine motor (d), expressive language (e), and early learning composite (f). The gray shading signifies the normal range for a given scale. Generalized estimating equations (GEE) determined whether the slopes of the lines differed between the diet groups (CMF8, EHF1-3, EHF8) and over time (5.5 to 8.5). The red line signifies a significant difference between EHF8 and CMF8; the blue line signifies a significant difference between EHF1-3 and CMF8.