Elemental dynamics in human milk: Composition, Holder pasteurization effects, and variability by maternal diet and lactation month

Holder pasteurization is routinely applied in human milk banks to ensure microbiological safety, although its impact on trace elements remains insufficiently described. This study aimed to assess pasteurization effects and variability associated with maternal diet and lactation month in human milk from Uruguayan women. Two analytical methods based on microwave plasma atomic emission spectrometry (MP AES and HG–MP AES) were optimized and validated. Limits of quantification ranged from 0.0018 to 0.014 mg L⁻¹, and trueness was verified using reference materials and spiked samples. In raw human milk samples from a Uruguayan milk bank, mean concentrations in colostrum (n=10) and mature milk (n=30) (mgL⁻¹) were: 0.0042/0.0036 (arsenic), 0.45/0.40 (copper), 2.5/1.9 (iron), 0.0030/0.0020 (lead), 0.0164/0.0132 (selenium), and 6.2/4.5 (zinc). Pasteurization caused significant losses only for selenium (up to 10.4% in colostrum, p<0.05). Milk from vegan mothers showed significantly lower concentrations of all evaluated elements than omnivores (n=16) (15–38% reduction, p<0.05). Despite this, recommended intakes would remain covered at typical consumption volumes. Additionally, a one-month follow-up in omnivorous mothers (n=16) revealed marked declines in copper, iron, selenium, and zinc (20–66%). This study provides the first multielement baseline for donated human milk in Uruguay and highlights factors influencing its nutritional quality. • First multielement baseline of human milk composition in Uruguay. • MP AES and HG–MP AES validated for trace elements in human milk. • Holder pasteurization caused only modest selenium losses. • Maternal diet significantly influenced milk trace element levels. • Trace elements generally met infant requirements despite variability.