Macronutrient variability in human milk from donors to a milk bank: Implications for feeding preterm infants

Abstract

Background and objective: The composition of human milk varies widely and impacts the ability to meet nutrient requirements for preterm infants. The purpose of this study is to use a large dataset of milk composition from donors to a milk bank to: (1) describe the macronutrient variability in human milk and how it contributes to the ability to meet the protein and calorie targets for the preterm infant using fortification with commercially available multi-nutrient fortifiers; (2) assess how temporal versus subject effects explain macronutrient variability; (3) determine how macronutrient variability contributes to the nutrient distribution in pooled donor milk.

Methods: This is a retrospective, observational study that analyzes the macronutrient data of 1,119 human milk samples from 443 individual donors to a milk bank. We test fortification strategies with potential basic, intermediate, and high protein and calorie commercial fortifiers. Additionally, we simulate the random pooling of multiple donors to model the impact of macronutrient variability on pooled donor milk.

Results: Fat was the most variable nutrient and accounted for 80% of the difference in calories. A subject-effect predicted more of the variability after 4 weeks postpartum in all macronutrients (R2 > = 0.50) than a time-effect (R2 < = 0.28). When pooling multiple donors, variability was reduced by increasing the number of donors randomly selected for a pool or targeted pooling based on macronutrient analysis of donor pools. Over 75% of mature milk samples fortified with a basic protein fortifier did not meet daily protein targets of 3.5 g/kg without exceeding volumes of 160 ml/kg/day.

Conclusion: There is a strong individual signature to human milk that impacts the pooling of donor milk, and the ability to meet protein and energy requirements for the preterm infant with basic and intermediate protein and calorie fortifiers.

Conflict of interest statement

EHS is the medical director for the Mothers' Milk Bank of North Texas. MTP serves on the Board of Directors for the Human Milk Banking Association of North America in an unpaid capacity. All other authors have declared that no competing interests exist. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1. Histograms and descriptive statistics for donor pools.

Represents Donor Pools > 4 weeks postpartum from 295 unique donors.

Fig 2. Box and whisker plots of feeding volumes to achieve various protein and calorie targets using commercial fortifiers.

Base (BASE), intermediate (INT), and high (HIGH) protein and calorie fortifiers in 443 Donor Pools from 443 unique donors providing either milk 4 weeks postpartum (N = 295). Grey rectangles represent quartile 1 to quartile 3 values. Within rectangles, the median is represented by–and the mean is represented by ◊. Reference lines: 200 ml/kg/day represents ESPGHAN maximum feeding volume; 160 ml/kg/day represents common NICU target volume.

Fig 3. Percent of pools by protein and fat content based on random pooling of 1 to 5 donors, or targeted pooling.

Dark bar represents percent of pools containing 1.0 g/dL of protein and 3.5 g/dL of fat.