Genetic and Physiological Factors Affecting Human Milk Production and Composition.

Yarden Golan,Yehuda G Assaraf

doi:10.3390/nu12051500

Abstract

Human milk is considered the optimal nutrition for infants as it provides additional attributes other than nutritional support for the infant and contributes to the mother’s health as well. Although breastfeeding is the most natural modality to feed infants, nowadays, many mothers complain about breastfeeding difficulties. In addition to environmental factors that may influence lactation outcomes including maternal nutrition status, partner’s support, stress, and latching ability of the infant, intrinsic factors such as maternal genetics may also affect the quantitative production and qualitative content of human milk. These genetic factors, which may largely affect the infant’s growth and development, as well as the mother’s breastfeeding experience, are the subject of the present review. We specifically describe genetic variations that were shown to affect quantitative human milk supply and/or its qualitative content. We further discuss possible implications and methods for diagnosis as well as treatment modalities. Although cases of nutrient-deficient human milk are considered rare, in some ethnic groups, genetic variations that affect human milk content are more abundant, and they should receive greater attention for diagnosis and treatment when necessary. From a future perspective, early genetic diagnosis should be directed to target and treat breastfeeding difficulties in real time.

Highlights

We have recently proposed that a haploinsufficiency state occurs in women harboring heterozygous mutations in SLC30A2/ZnT2, which implies that a single gene copy of the wild type (WT) allele is not sufficient for the secretion of zinc into the milk to meet the infant’s nutritional needs [32]
We have further reported that the frequency of individuals harboring Transient Neonatal Zinc Deficiency (TNZD) causing alleles was as high as 1 in 2334 individuals from various ethnic groups [34]
The author suggested that during the Last Glacial Maximum (LGM; 28,000–18,000 years ago), people were living in Arctic Beringia and were exposed to very low levels of UV radiation, which can lead to dangerously low levels of biosynthesized vitamin D [139]

Summary

Introduction

Hormones including estrogen initiate mammary gland development to support lactation [1,2,3]. Later, during pregnancy, elevated levels of progesterone and prolactin initiate the alveolar development in the mammary gland as well as the proliferation of mammary gland epithelial cells [4]. The lactogenic hormones estrogen, progesterone, and prolactin and metabolic hormones such as insulin are required for the differentiation of mammary epithelial secreting cells, which are capable of synthetizing and secreting specific milk components. This process is termed “secretory differentiation” and it continues during pregnancy [5,6]

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Discussion

Conclusion