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Title: Infant diet, gender and the normative development of vagal tone and heart period during the first two years of life

Author
item PIVIK, R - Arkansas Children'S Nutrition Research Center (ACNC)
item ANDRES, ALINE - Arkansas Children'S Nutrition Research Center (ACNC)
item TENNAL, KEVIN - Arkansas Children'S Nutrition Research Center (ACNC)
item GU, YUYUAN - Arkansas Children'S Nutrition Research Center (ACNC)
item ARMBYA, N - University Arkansas For Medical Sciences (UAMS)
item CLEVES, MARIO - Arkansas Children'S Nutrition Research Center (ACNC)
item Badger, Thomas - Arkansas Children'S Nutrition Research Center (ACNC)

Submitted to: International Journal of Psychophysiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2013
Publication Date: 10/15/2013
Citation: Pivik, R.T., Andres, A., Tennal, K., Gu, Y., Armbya, N., Cleves, M.A., Badger, T.M. 2013. Infant diet, gender and the normative development of vagal tone and heart period during the first two years of life. International Journal of Psychophysiology. 90(3):311-320.

Interpretive Summary: How do differences in early infant diet affect the development and control of heart rate? We studied these questions by analyzing resting heart rate recordings at 3, 6, 9, 12, and 24 months in healthy breastfed, milk formula-fed, or soy formula-fed infants. Heart rate slowed with age for all groups and was faster in girls than boys, particularly among soy-fed infants. Vagal tone--a measure of autonomic activity that works to slow heart rate--was higher for girls than boys across groups and higher in formula-fed than breastfed infants, particularly among boys. These findings suggest infant diet may help determine individual differences in functions such as attention, emotion, and cognition known to be influenced by heart rate regulation. Contrary to concerns about the safety of soy formula, our findings of more consistent differences in heart rate between soy-fed boys and girls and higher vagal tone in soy-fed boys than other boys suggest developmental advantages may be conferred by this formula.

Technical Abstract: Relationships between early postnatal diet and the development of cardiac regulation were studied using resting vagal tone and heart period measures obtained quarterly during infancy and at 2 years in 158 breast-fed, 159 milk formula-fed, and 148 soy formula-fed infants. Both measures increased across time for all groups. Heart period was greater in boys than girls--particularly in soy-fed infants. Higher vagal tone in girls than boys was not strongly influenced by diet. At 1 and 2 years, measures differed among boys (soy-fed > breast-fed) but not girls. Earlier slowing in breast-fed than formula-fed infants in the rate of increase in vagal tone during infancy suggests the timing of this developmental shift is sensitive to early infant diet. Finally, greater heart period gender differentiation in soy-fed infants and higher vagal tone in soy-fed boys than other boys may imply developmental advantages associated with soy formula.