How much human milk do infants consume? Data from 12 countries using a standardized stable isotope methodology

Abstract

The WHO has developed new growth curves based on breast-fed infants. Recommendations for energy intake have been adopted based on measurements of total energy expenditure. Data on human milk (HM) intake are needed to estimate the energy intake from this food source. However, objective HM data from around the world have not been available, because these measurements are difficult to obtain. Stable isotope methods have been developed to provide objective measurements over a 14-d period. A pooled analysis of 1115 data points of HM intake, obtained using the dose to the mother deuterium oxide turnover method, was undertaken in infants aged 0-24 mo from 12 countries across 5 continents. A hierarchical model was needed to estimate mean HM intake and its variance within and between countries given the complexity of the data. The overall mean HM intake was 0.78 (95% CI = 0.72, 0.84) kg/d, and the age-specific estimates indicated that intake increased over the first 3-4 mo and remained above 0.80 kg/d until 6-7 mo. The variability of intake increased in late infancy. Boys consumed 0.05 kg/d more than girls (P < 0.01). HM intake was strongly, inversely associated with non-HM water intake [r = -0.448 (95% CI -0.511 to -0.385); P < 0.0001]. These objective isotope values of HM intake improve our understanding of the magnitude and variability of HM intake within and across populations and help to estimate nutrient intakes in breast-fed infants.

FIGURE 1

Two compartment, steady-state model of water flows in a mother and her PBF infant. The subscripts b, m, and o refer to the infant, mother, and outside, the combined subscripts indicate directions of water flow (e.g. bm is to the infant from the mother; mo to the mother from the outside). Qm and Qb refer to the total ²H₂O distribution space of mother and infant, respectively.

FIGURE 2

Growth curve for weight-for-age for male (A) and female (B) infants included in the Human Milk Intake Analysis. Values are mean ± SD, n = 8–142 (A) or 12–124 (B). Lines are WHO standards for 5th, 50th, and 95th percentiles (1). There are no data available for 11-mo-old infants.

FIGURE 3

Hierarchical model for HM intake obtained with the dose-to-the-mother deuterium oxide method according to infant age group. This model estimates an overall HM intake with random effect terms for between-country SD and between-individual, within-country SD. The values are mean HM estimates and 95% CI from the hierarchical model with categorical age. There are no available data for 10- to 11-mo-old infants and data for infants ≥12 mo old were grouped. The sample size is included on the top axis. The star plotted in the graph indicates the intake of HM reported by WHO (4) for exclusively HM-fed infants from 1 to 11 mo of age from developed countries.