Concentrations and predictors of select nutrients in Canadian human milk samples from the MIREC pregnancy cohort.

Kathryn E Hopperton, Erica O’Neill, Subhadeep Chakrabarti, Melanie Stanton, Sophie Parnel, Tye E Arbuckle, Jillian Ashley-Martin, Jesse Bertinato, Maryse F Bouchard, Michael M Borghese, Stephen Brooks, Kevin Cockell, Robert Dabeka, Meong Jin Joung, Bruce P Lanphear, Pascal Lapointe, Amanda J MacFarlane, Susan MacPherson, John Krzeczkowski, Dorothea F K Rawn, Peter von Dadelszen, Hope A Weiler, Chao Wu Xiao, Mandy Fisher. American Journal of Clinical Nutrition 2024 Oct 1:S0002-9165(24)00805-0. doi: 10.1016/j.ajcnut.2024.09.029

Question: What are the concentrations and sources of variability of nutrients in human milk?

The concentrations of nutrients in human milk (breastmilk) are widely used in clinical, regulatory, and public health initiatives. Examples include development of Dietary Reference Intakes (DRIs) and dietary guidelines, and the regulation of nutrient levels in infant formulas. The majority of existing data in the American and Canadian food composition databases are outdated and now considered inappropriate to estimate current nutrient intakes.

What did the researchers do:
Human milk samples (n = 559-835, depending on nutrient) provided by MIREC participants at 3-10 weeks after delivery were analyzed for minerals (calcium, magnesium, phosphorus, potassium, sodium, manganese, molybdenum, zinc, copper, iodine, selenium), vitamin D, folates, and fatty acids. Researchers at Health Canada examined associations between participant characteristics and nutrient concentrations using various statistical methods.

What did they find:
Concentrations of human milk nutrients in MIREC samples were within the range observed in the scientific literature except for manganese, which was >100-fold lower than the value in the existing Canadian nutrient databank profile [2.43 (standard deviation 2.84) compared with 260 ng/g]. Concentrations of folates, vitamin D, and fatty acids demonstrated greater variability with maternal and sample characteristics than the minerals. Factors such as dietary supplement use, body mass index, and for vitamin D, skin color and season, had an impact on nutrient concentrations.

What does this mean:
This research fills important knowledge gaps regarding the concentrations and sources of variability in human milk nutrients and will support the development of future reference values based on human milk. This study is the largest published to date in a high or middle-high-income country using appropriate methods for the minerals measured. MIREC participants have made a very important contribution to developing reference values for nutrients in human milk and infant formulas.

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