Impact of Lactation Patterns on the Hormonal Composition of Human Breast Milk

Abstract

Background: In addition to providing nutrients, human breast milk (HBM) delivers non-nutritive bioactive elements, including glucocorticoids (GCs; cortisol and cortisone) to breastfeeding (BF) infants. Milk-borne GCs are important regulators of stress-mediated responses and may influence infant physiological and psychological development. Many factors are known to influences maternal stress, and hence the GC composition of breast milk. However, little is known about how partial BF (which affects milk volume, and frequency and regularity of feeding) may influence GC hormone levels in HBM. We hypothesised that different BF patterns have a major impact on the composition and volume of milk-borne GCs. Objective: To determine the variation of GC steroid hormone concentrations in HBM related to different breastfeeding patterns (exclusive vs partial BF). Methods: Samples were obtained from lactating mothers participating in the Finnish STEP study (Steps to the Healthy Development and Well-being of Children). GC concentrations were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in 652 samples adjusting for infant sex. Data on BF patterns and infant gender were obtained using self-reported diaries and hospital records. Results: Cortisone (mean 9.5 ng/ml) and cortisol (mean 7.5 ng/ml) were detected in all samples. Infant gender had no impact on GC concentrations. Furthermore, no difference in GC levels was observed between the exclusive and partial BF groups. Conclusion: GC levels in HBM are not associated with variation of BF pattern or with infant gender. Further analysis is ongoing to determine the impact of maternal health and nutritional intake on GC levels in HBM.