Longitudinal variations of macro- and trace elements in human milk (HM) are not well characterised, and therefore, the recommendations for intake for Australian infants require more evidence to ensure accuracy. We aimed to investigate the longitudinal variation of HM macro- and trace-element concentrations (1-12 months) and infant intake (1-6 months) and to investigate the relationships between intake and infant growth parameters at 3 and 6 months, and determine if intake was sufficient when compared to national guidelines. HM samples were collected monthly for the first 6 months and then at 9 and 12 months postpartum from mother-infant dyads (n = 83). Test-weighing was used to determine the volume of HM consumed daily. Element concentrations (Na, Ca, K, Mg, P, I, Se, Zn, Cu, Mn, Mo, and Fe) were measured using ICP-MS, and intake was calculated using the measured concentrations and the volume of HM consumed. The average intake of HM was 776.3 ± 24.0 mL for the infants. Changes in concentration from months 1 to 12 postpartum were observed for all the measured micronutrients (all p < 0.05). The calculated intakes of all the macro- and trace elements showed that 0% to 82% of infants met the current adequate recommendations at varying periods of lactation. The calculated macro- and trace-element intakes were below the adequate intake recommendations, suggesting that they are not reflective of healthy infant requirements. These findings suggest the need for larger studies using sensitive analytical techniques and the revision of current recommendations for breastfed infants.
Keywords: breastfeeding; human milk; intake; lactation; macro-element; minerals; trace element.