Macronutrient composition of donor human milk from the first human milk bank in New Zealand

A human milk diet for preterm infants is associated with significant reductions in the incidence and severity of several prematurity-related morbidities, such as Necrotizing Enterocolitis (1) . When a mother’s own milk is not available, donor human milk (DHM) is recommended as the best alternative by the ESPGHN (2) and the AAP (3) . Although DHM is crucial for supporting the health of preterm infants, it’sits macronutrient composition is known to vary significantly, which poses challenges for fortification and clinical use (4) . The present study is an observational, secondary data analysis which aims to describe the energy and macronutrient (fat, true protein and total carbohydrate) content of DHM from the Christchurch Women’s Hospital Milk Bank in New Zealand. 784 samples of single-donor pooled, pasteurised DHM from 163 unique donors were analysed with the Miris Human Milk Analyser. Preliminary descriptive analysis was completed by using Microsoft Excel, expressed as mean (standard deviation), minimum and maximum values) were calculated using Microsoft Excel. The proportion of milk being donated to the milk bank was: 62.4% mature term (n = 489), 35.5% mature preterm (n = 278), 1.8% preterm colostrum (n = 14), 0.4% term colostrum (n = 3). Mature preterm milk contained on average 77.7 (22.3) kcal/100 mL energy; 4.2 (1.9) g/100 mL fat; 1.4 (0.4) g/100 mL true protein; and 8.3 (1.8) g/100 mL total carbohydrate. Mature term milk contained 73.2 (27.1) kcal/100 mL energy; 3.9 (2.5) g/100 mL fat; 1.0 (0.5) g/100 mL true protein; and 8.1 (0.9) g/100 mL total carbohydrate. Macronutrient and energy content of preterm and term colostrum were also reported descriptively. Wide variability was observed in the nutrients across samples. Term milk energy ranged from 39.3 – 254.0 kcal/100 mL, fat ranged from 0.5 – 18.8 g/100 mL, true protein from 0.3 – 9.8 g/100 mL, and total carbohydrate from 0.8 – 9.4 g/100 mL. Similarly, preterm milk showed energy ranging from 47.7 – 153.7 kcal/100 mL, fat from 1.2 – 12.7 g/100 mL, true protein from 0.4 – 4.6 g/100 mL, and total carbohydrate from 1.8 – 35.0 g/100 mL. The wide variability observed aligns with existing literature on DHM and likely reflects donor biology, processing and handling, and milk expression practices. This research contributes to the evidence base on the composition of DHM in New Zealand. Further analysis using this dataset will explore the relationship between macronutrient composition and donor variables (postpartum period, age and ethnicity) to better understand their implications for DHM composition and clinical use.