Variability of Water-Soluble Forms of Choline Concentrations in Human Milk during Storage, after Pasteurization, and among Women.

Choline is critical for infant development and mother's milk is the sole source of choline for fully breastfed infants until six months of age. Human milk choline consists to 85% of water-soluble forms of choline including free choline (FC), phosphocholine (PhosC), and glycerophosphocholine (GPC). Donor milk requires safe handling procedures such as cold storage and pasteurization. However, the stability of water-soluble forms of choline during these processes is not known. The objectives of this research were to determine the effect of storage and pasteurization on milk choline concentration, and the diurnal intra- and inter-individual variability of water-soluble choline forms. Milk samples were collected from healthy women who were fully breastfeeding a full-term, singleton infant <6 months. Milk total water-soluble forms of choline, PhosC, and GPC concentrations did not change during storage at room temperature for up to 4 h. Individual and total water-soluble forms of choline concentrations did not change after storage for 24 h in the refrigerator or for up to one week in the household freezer. Holder pasteurization decreased PhosC and GPC, and thereby total water-soluble choline form concentrations by <5%. We did not observe diurnal variations in PhosC and total water-soluble forms of choline concentrations, but significant differences in FC and GPC concentrations across five sampling time points throughout one day. In conclusion, these outcomes contribute new knowledge for the derivation of evidence-informed guidelines for the handling and storage of expressed human milk as well as the development of optimized milk collection and storage protocols for research studies.

Relationships among Different Water-Soluble Choline Compounds Differ between Human Preterm and Donor Milk.

Choline is essential for infant development. Human milk choline is predominately present in three water-soluble choline (WSC) forms: free choline (FC), phosphocholine (PhosC), and glycerophosphocholine (GPC). It is unclear whether mother's own preterm milk and pooled donor milk differ in WSC composition and whether WSC compounds are interrelated. Mother's own preterm milk (n = 75) and donor milk (n = 30) samples from the neonatal intensive care unit, BC Women's Hospital were analyzed for WSC composition using liquid chromatography tandem mass spectrometry (LC-MS/MS). Associations between different WSC compounds were determined using Pearson's correlations, followed by Fischer r-to-z transformation. Total WSC concentration and concentrations of FC, PhosC, and GPC did not significantly differ between mother's own milk and donor milk. FC was negatively associated with PhosC and GPC in mother's own milk (r = -0.27, p = 0.02; r = -0.34, p = 0.003, respectively), but not in donor milk (r = 0.26, p = 0.181 r = 0.37, p = 0.062, respectively). The difference in these associations between the two milk groups were statistically significant (p = 0.03 for the association between PhosC and FC; and p = 0.003 for the association between FC and GPC). PhosC and GPC were positively associated in mother's own milk (r = 0.32, p = 0.036) but not donor milk (r = 0.36, p = 0.062), although the difference in correlation was not statistically significant. The metabolic and clinical implications of these associations on the preterm infant need to be further elucidated.