Sex-Specific Human Milk Composition: The Role of Infant Sex in Determining Early Life Nutrition

Abstract

Male and female infants respond differentially to environmental stimuli, with different growth and neurodevelopmental trajectories. Male infants are more likely to be disadvantaged when subjected to adversity and show a higher risk of perinatal complications. However, the underlying causes of this sex-bias are not well defined and optimising the early life nutritional care may be necessary to minimise the “male disadvantage” that may be experienced early in life. Experimental models have demonstrated that animal milk composition differs according to offspring sex, suggesting that the tailoring of early life nutrition may be one mechanism to maximise health protection and development to infants of both sexes. However, evidence for a sex-specificity in human milk composition is limited and conflicting, with studies documenting higher milk energy content for either male or female infants. These data show sex differences, however, there has been limited compositional analysis of the current data nor strategies proposed for how sex-specific compositional differences in early life nutrition may be used to improve infant health. The present narrative review highlights that an improved understanding of sex-specific human milk composition is essential for promoting optimal infant growth and development.

Steroid hormone concentrations in milk predict sex‐specific offspring growth in a nonhuman primate

“…Conversely, among males, growth was not predicted by cortisol but rather positively predicted by DHEAS concentrations at early lactation and by increases in milk DHEAS concentrations from early to peak and peak to late lactation. These results contribute to the growing body of evidence for sex‐differentiated mechanisms underlying physiological processes during early development in other animals (Badyaev, ; Brummelte, Lieblich, & Galea, ; Carpenter, Grecian, & Reynolds, ; Galante et al, ). For example, among rhesus macaques in this population, the quantity and quality of milk differs by offspring sex (Hinde, ), and male and female offspring differ in sensitivity to maternal milk cortisol in relation to temperament (Hinde et al, ).…”

Neutral Human Milk Oligosaccharides Are Associated with Multiple Fixed and Modifiable Maternal and Infant Characteristics

“…In secretors, mothers of boys had higher concentrations of LNFP-I, LNH, LNnH, IFLNH-I, IFLNH-III and DFLNH-a&c than those of girls. The difference in perinatal outcomes between males and females has been recognized as the "male disadvantage" since the 1970s [49]. Boys may need more HMOs than girls, and this theory needs further studies.…”

Sexually Dimorphic Associations between Maternal Factors and Human Milk Hormonal Concentrations

“…Extensive evidence from animal models has shown that these compounds are likely to be active in HM and, once ingested by the infant, exert a range of physiological functions [5]. Changes in HM nutritional and hormonal composition have been well documented throughout the sequential stages of lactation [6,7], per feed [8], per day [9], across mothers with different phenotypic characteristics [10,11], socioeconomic status [12] and infants of different sex [13]. Limited studies to date [11,[14][15][16][17] have reported alterations in the HM bioactive, amino and fatty acid profiles of women with gestational diabetes mellitus (GDM) or elevated body mass index (BMI), suggesting that HM may have different nutritional and hormonal composition associated with individual maternal characteristics.…”