Centering human milk composition as normal human biological variation

Abstract

Objectives: Human biological variation in the phenotype is the cornerstone of modern human biology, evolutionary anthropology, and related studies of human evolution. Minimal dialogue, however, has considered human milk to be part of this phenotypic variation. This may reflect researcher bias-mental models oriented around commercial infant formula and homogenized cow's milk, both of which present milk composition as static. A general lack of research outside primarily Western, well-nourished populations has also contributed to this underestimation of biological variation.

Methods: This review analyzes published research on breast milk composition, developmental metabolic programming, and maternal body composition to articulate the ways in which population-based studies of human milk outside the United Sates are necessary to better understanding biological variation in human milk phenotypes.

Results: This review discusses some of the common issues in current research on the biological variation in human milk composition and argues that anthropological inquiries that frame milk as part of an adaptive phenotype are necessary to better understand the biological significance of human milk composition in the production of human biological variation.

Conclusions: Biological anthropology is uniquely positioned to investigate biological variation in human milk, using evolutionary theory, cutting edge biology, and anthropologically informed perspectives that challenge the biomedical framing of lactation and often act to privilege well nourished, primarily western populations and formula feeding as normatives for infant feeding research.