Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/22/2005
Publication Date: 10/6/2005
Citation: Pivik, R.T. 2005. Preliminary results of a longitudinal study of infants fed soy formula: brain development and function. In: Proceedings of the "Effects of Soy on Growth and Development: How Much Do We Know?", Chicago, Illinois. 2005 CDROM.
Interpretive Summary: This is a report from our study that looks at how what healthy babies eat may change their behavior. Babies were breast or formula (milk or soy) fed at least since they were 2 months old. We looked at mental and motor skills and brain activity at rest and in response to speech sounds in 3- and 6-month-old babies. All measures were in the normal range across groups, but there were diet-related differences. Motor skills were better in babies fed breast milk and milk formula than soy formula. The groups showed some differences in the reactions to speech sounds, but formula diets had similar effects on these responses. These are early results, and we need more data to confirm these findings.
Technical Abstract: Previous studies of early developmental EEG activity (spontaneous and evoked) have not considered the influence of diet on these processes. However, nutritional status and dietary factors are well known to influence brain development and function. This investigation compared measures of behavioral development (Bayley Mental and Motor Scales), resting EEG activity, and event-related potentials (ERPs) to speech stimuli at 3 and 6 months in healthy full-term infants belonging to three, self-selected infant diet groups: exculsively breast-fed (BR: n=21, 11 males), or fed either milk-based formula (MF: n=21, 11 males) or soy-based formula (SF: n=21, 11 males) since at least 2 months of age. Recordings [high-density (128 sites)] were conducted while infants were awake and resting quietly (spontaneous EEG) or while speech stimuli were being presented (ERPs to two syllables: /pa/ and /ba/ randomized 80%:20% occurrence, respectively; duration: 300ms, 72 dB, ISI: 2550ms, sampling rate: 250 Hz; 180-270 trials). Data reported were recorded from left anterior temporal sites. Behavioral, EEG, and ERP data were analyzed using ANOVA procedures with post-hoc t-tests. All groups scored within the normal range on Bayley Mental and Motor scales. There were no significant differences among groups on Mental scores at either test period. Even though Motor scores were within the normal range and did not differ significantly between SF and MF at 3 months or SF and BF at 6 months, Motor scores for SF infants were lower (P<0.05) than those of BF infants at 3 months and MF infants at 6 months. Resting EEG activity was similar across groups at 3 months. An increase in 3-6 Hz activity present at 6 months in MF and SF, but no BF infants, is likely related to feeding near the time of the recordings. Speech stimuli elicited two positive peaks at ~ 170 ms (P1) and ~350 ms (P2) which have been associated with processing of acoustic and phonemic stimulus features, respectively. Response amplitudes across syllable types were highest in BF infants at 3 months (BF>MF=SF). Relative to 3-month responses, there was an overall response amplitude reduction at 6 months in BF but not formula-fed infants. At the group level, speech syllable discrimination-- as reflected in P2 amplitude differences to the two syllables -- was consistently greatest in BF infants, apparent in SF infants at 3, but not at 6 months, and least apparent in MF infants at either test period. These results suggest the presence of significant differences between healthy breast-fed and formula-fed infants in behavioral development and processing speech sounds early in development. The general equivalence between milk-based formula and soy-based formula groups on behavioral measures and brain responses to speech stimuli during this formative developmental period is notable. It is important to recognize that these results are based on preliminary data from a small subset of infants enrolled in a longitudinal study, and more data are needed before reliable conclusions can be drawn. The differences between groups may reflect dietary influences on the temporal acquisition and/or extinction of developmentally acquired functions, or they may just reflect the small numbers of subjects.