Bert J. M. van de Heijning, Bernd Stahl, Maaike W. Schaart, Eline M. van der Beek, Edmond H. H. M. Rings, M. Luisa Mearin
Background: Longitudinal data on the composition of human milk in cohorts of term infants are limited but warranted. In the PreventCD cohort, human milk samples were collected monthly over 6-9 consecutive months enabling longitudinal analysis of macronutrient composition. Methods: Milk sample series from 25 lactating women were analysed for fatty acid (FA) and amino acid (AA) content and composition; also total N-content was assessed. Mainly mature (i.e. >15 days after delivery) milk samples were collected. Milk content and composition were related to the gender and bimonthly weight accrual of the infant up to 6 months of age. Results: As sample collection was not standardised for time of day nor for fore- or hindmilk, a large monthto- month variation in fat and protein levels was observed within and between donors. In spite of the quantitative variability, the quality (i.e. composition) of both lipids and protein in the samples obtained was relatively stable. Also, the average content and composition of FA as well as AA remained quite stable over the lactation period. Milk macronutrient content or composition was not different between genders, and bimonthly body weight accrual of the offspring was not associated with milk FA or AA content. Conclusions: These results show that the inter- and intra-individuality of human milk composition are limited, regardless of sampling procedures. The average composition of the samples showed a stable pattern both in FA and AA profile during lactation.