Human milk macronutrients and child growth and body composition in the first 2 years: a systematic review

Authors: REYES, SARAH - University Of Manitoba; BROCKWAY, MERILEE - University Of Manitoba; MCDERMID, JOANN - University Of Virginia; CHAN, DEBORAH - University Of Manitoba; GRANGER, MATTHEW - University Of Manitoba; REFVIK, REBECCA - University Of Manitoba; SIDHU, KARANBIR - University Of Manitoba; MUSSE, SUAD - University Of Manitoba; MONNIN, CAROLINE - University Of Manitoba; LOTOSKI, LARISA - University Of Manitoba; GEDDES, DONNA - The University Of Western Australia; JEHAN, FYEZAH - Aga Khan University; KOLSTEREN, PATRICK - Ghent University; Allen, Lindsay - A; HAMPEL, DANIELA - University Of California, Davis; ERIKSEN, KAMILLA - University Of Copenhagen; RODRIGUEZ, NATALIE - University Of Manitoba; AZAD, MEGHAN - University Of Manitoba

Submitted to: Advances in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2023
Publication Date: 6/13/2023
Citation: Reyes, S.M., Brockway, M., Mcdermid, J.M., Chan, D., Granger, M., Refvik, R., Sidhu, K., Musse, S., Monnin, C., Lotoski, L., Geddes, D., Jehan, F., Kolsteren, P., Allen, L.H., Hampel, D., Eriksen, K.G., Rodriguez, N., Azad, M.B. 2023. Human milk macronutrients and child growth and body composition in the first 2 years: a systematic review. Advances in Nutrition. https://doi.org/10.1016/j.advnut.2023.06.005.
DOI: https://doi.org/10.1016/j.advnut.2023.06.005

Interpretive Summary: Human milk (HM) fat, protein, and carbohydrates (macronutrients) are the main sources of energy for the infant in the first years of life. While these macronutrients have been well studied, their role in infant growth is still poorly understood. Therefore, we systematically reviewed evidence published between 1980-2022 on HM components and anthropometry through 2 years of age among term-born infants. 9,992 abstracts were screened and 58 articles from 53 studies were included, representing 5,979 mother-infant pairs. There were substantial differences in sample collection among the studies and less information was available on diurnal compositional variability in HM macronutrient content. Generally, carbohydrates were positively related to infant weight, and protein to infant length. Evidence on HM fat associations with infant outcomes were scarce and inconclusive. Fatty acid intakes were generally positively associated with head circumference, excluding saturated fatty acids and n-6 polyunsaturated fatty acids. Our review was limited by methodological and sample collection differences, as well as by insufficient reporting of results. HM researchers should use validated milk analysis techniques to assess macronutrient content and develop consistent sampling protocols that include data of variation in HM macronutrients throughout a day.

Technical Abstract: Human milk (HM) macronutrients contribute the majority of infant energy intake in the first years of life. Consisting of digestible carbohydrates (lactose, glucose and fructose), proteins and amino acids, as well as fats and fatty acids, HM macronutrients have been well studied; however, their role in infant growth is still poorly understood. We systematically searched Medline, EMBASE, the Cochrane Library, Scopus, and Web of Science to synthesize evidence published between 1980-2022 on HM components and anthropometry through 2 years of age among term-born infants. From 9,992 abstracts screened, 139 articles were included and categorized based on their reporting of HM micronutrients, macronutrients, or bioactive components. Macronutrient components are reported here, based on 58 articles from 53 studies reporting observations from 5,979 dyads. There was substantial heterogeneity in sampling strategies and many studies did not sufficiently capture diurnal compositional variability in HM macronutrient content. In general, carbohydrates and HM sugars were positively associated with infant weight outcomes. Protein demonstrated a positive association with infant length, but no associations were reported for infant weight. Finally, HM fat demonstrated mixed associations with infant growth with only single studies demonstrating associations. Fatty acid intakes were generally positively associated with head circumference, with the exception of saturated fatty acids and n-6 polyunsaturated fatty acids. Our synthesis of the literature was limited by methodological differences and issues with milk collection strategies, as well as by insufficient reporting of results. Moving forward, HM researchers should use validated milk analysis techniques to assess macronutrient content and develop consistent sampling protocols that are reflective of the temporal variation in HM macronutrients.