Near-infrared reflectance analysis to evaluate the nitrogen and fat content of human milk in neonatal intensive care units

Objective: To validate near-infrared reflectance analysis (NIRA) as a fast reliable and suitable method for routine, evaluation of human milk's nitrogen and fat content. Setting: One neonatal intensive care unit. Patients: 124 samples of expressed human milk (55 from preterm mothers and 69 from term mothers). Intervention: Measurement of nitrogen and fat content by NIRA and traditional methods (Gerber method for fat and Kjeldahl method for nitrogen). Main outcome measures: Agreement between NIRA and traditional methods. Variability in fat and nitrogen content of human milk. Results: A strong agreement was found between the results of traditional methods and NIRA for both fat and nitrogen content (expressed as g/100 g of milk) in term (mean fat content: NIRA = 2.76; Gerber = 2.76; mean nitrogen content: NIRA = 1.88; Kjeldahl = 1.92) and preterm (mean fat content: NIRA = 3.56; Gerber = 3.52; mean nitrogen content: NIRA = 1.91; Kjeldahl = 1.89) mothers' milk. Nitrogen content of the milk samples, measured by NIRA, ranged from 1.18 g/100 g to 2.71 g/100 g of milk in preterm milk and from 1.48 g/100 g to 2.47 g/100 g in term milk; fat content ranged from 1.27 g/100 g to 6.23 g/100 g of milk in preterm milk and from 1.01 g/100 g to 6.01 g/100 g of milk in term milk. Conclusion: NIRA can be used as a quick and reliable tool for routine monitoring of macronutrient content of human milk and for devising individualised human milk fortification regimens in the feeding of very premature infants.