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Infant sex predicts breast milk energy content
Author(s) -
Powe Camille E.,
Knott Cheryl D.,
ConklinBrittain Nancy
Publication year - 2009
Publication title -
american journal of human biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.559
H-Index - 81
eISSN - 1520-6300
pISSN - 1042-0533
DOI - 10.1002/ajhb.20941
Subject(s) - breast milk , pregnancy , breast feeding , infant development , lactation , medicine , breastfeeding , physiology , demography , obstetrics , biology , pediatrics , developmental psychology , psychology , biochemistry , genetics , sociology
Abstract During human evolutionary history, and for many around the world, breast milk is the primary source of nutritional energy for infants. Variation in breast milk quality might logically have important effects on infant health, growth, and development, yet the sources of this variation remain largely unelucidated. We quantified nutrient and energy content of breast milk from 25 healthy, well‐nourished Massachusetts mothers with infants aged 2–5 months. We examined several potential sources of variation in milk quality, particularly feeding patterns, infant sex, and maternal breast growth during pregnancy. After controlling for time since last feeding, a known correlate of milk composition, we found that mothers of male infants produced milk that had 25% greater energy content than mothers of female infants ( P < 0.001). Change in maternal bra cup size during pregnancy was associated with 16.17 kcal/100 ml greater energy content of milk ( P = 0.009), but was not significant after taking infant sex into account. Greater nutritional investment in sons may account for the greater observed growth rates in male compared to female infants. Am. J. Hum. Biol. 2010. © 2009 Wiley‐Liss, Inc.