Relation Between Human Milk Sodium and Maternal Sodium Intake

Sodium is an essential mineral, necessary for optimal development of an infant. However, its content in human milk is highly variable. The main factors influencing sodium content in human milk are the concentration of other osmoles (dominantly lactose) and time postpartum. It is still debatable if maternal sodium intake affects sodium content in human milk. Overall, Latvian inhabitants consume more sodium than recommended. Therefore, we aimed to analyse the relation between maternal sodium intake and human milk sodium content. In total, 64 human milk samples and food data from 64 participants were obtained. Sodium content was determined using inductively coupled plasma mass spectrometry. Food diary data was analysed using Finnish database Fineli. The results showed that median sodium content in human milk was 12.67 mg per 100 ml⁻¹. Nevertheless, large inter-individual differences were observed (5.00–42.54 mg·100 ml⁻¹). Sodium in-take among the participants was higher than the recommended 2000 mg per day (median intake — 2335.83 mg per day). Although a positive association was found between median maternal sodium intake and sodium content in human milk (ρ= 0.350, p = 0.010), a hierarchical multiple regression revealed that only infant’s age was a significant factor (p = 0.038), explaining 13% of the variability of sodium content in human milk. Sodium content in human milk is not influenced directly by maternal sodium intake, and other factors (such as lactose and potassium concentration in human milk not considered in the study) could potentially influence sodium content in human milk.