Human Milk Nutrient Composition Data is Critically Lacking in the United States and Canada: Results from a Systematic Scoping Review of 2017-2022

Abstract

Characterization of the nutrients in human milk is important to understand the dietary and developmental requirements of infants. The objective of this review was to summarize the state-of-the-science on the nutrient composition of human milk in the United States and Canada published from 2017 to 2022. Four databases were searched for randomized controlled studies and others given the scoping nature of this review. We limited type to mature milk collected 21 d postpartum and beyond from lactating individuals in the United States and Canada who gave birth at 37-wk gestation or later (full-term). Outcomes of interest included traditional macro- and micronutrients, including human milk oligosaccharides (HMOs), and milk volume. The publication date range was selected as January 1, 2017, to the day the literature search was performed. A total of 32 articles were included in the scoping review from primarily longitudinal cohort or cross-sectional designs. The most prevalent sample collection method was full-breast expression (n = 20) with most studies (n = 26) collecting samples from a single timepoint. Carbohydrates (HMOs [n = 12], glucose [n = 8], and lactose [n = 6]) and protein (n = 5) were the most frequently assessed nutrients in this body of work, with consensus among studies that glucose is present in limited concentrations compared to lactose (24-64 mg/dL compared with 6-7 g/dL) and that HMOs are influenced by temporality and secretor status. Included studies displayed an overall level of heterogeneity and sparsity paralleling previous reports and nutrient data in the USDA FoodData Central system. Much of the data extracted from retained articles generally provided analysis of a specific nutrient or group of nutrients. Moreover, many studies did not use the preferred analytical methods as outlined by the Human Milk Composition Initiative to increase measurement confidence. Up-to-date nutrient composition data of human milk is still greatly needed as it is paramount for the management of infant feeding, assessment of infant and maternal nutritional and health needs, and as a reference for infant formula development.

Keywords: USDA Food Data System; breast milk; maternal health; minerals; nutrition; pediatrics; vitamins.

FIGURE 1

Analytical framework used to guide the scoping review of nutrient composition of human milk in the United States and Canada from studies published from 2017 to 2022. Abbreviations: DRI, Dietary Reference Intake; HMO, human milk oligosaccharide.

FIGURE 2

Flow diagram of study identification and screening process according to the 2020 PRISMA guidelines. Note: ∗Denotes studies that did not use preferred methods.

FIGURE 3

(A) Number of articles published from 1980 to 2022 using the search term ‘human milk’ (PubMed, 1 January, 1980, to 31 December, 2022). (B) Number of articles from the included studies that reported on a particular nutrient. (C) Heatmap of nutrients assessed by each included study. Intensity of cell color is based on number of sample collections. Abbreviation: HMO, human milk oligosaccharide.