Vittoria Paoletti

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.

Protein content and fortification of human milk influence gastroesophageal reflux in preterm infants.

Objectives: Preterm human milk (HM) may provide insufficient energy and nutrients and thus may need to be fortified. Our aim was to determine whether fat content, protein content, and osmolality of HM before and after fortification may affect gastroesophageal reflux (GER) in symptomatic preterm infants. Methods: Gastroesophageal reflux was evaluated in 17 symptomatic preterm newborns fed naïve and fortified HM by combined pH/intraluminal-impedance monitoring (pH-MII). Human milk fat and protein content was analysed by a near-infrared reflectance analysis. Human milk osmolality was tested before and after fortification. Gastroesophageal reflux indexes measured before and after fortification were compared and were also related to HM fat and protein content and osmolality before and after fortification. Results: An inverse correlation was found between naïve HM protein content and acid reflux index (RIpH: P = 0.041, ρ =−0.501). After fortification, osmolality often exceeded the values recommended for infant feeds; furthermore, a statistically significant (P < 0.05) increase in nonacid reflux indexes was observed. Conclusions: Protein content of naïve HM may influence acid GER in preterm infants. A standard fortification of HM may worsen nonacid GER indexes and, due to the extreme variability in HM composition, may overcome both recommended protein intake and HM osmolality. Thus, an individualised fortification, based on the analysis of the composition of naïve HM, could optimise both nutrient intake and feeding tolerance.

Lack of correlation between fecal elastase-1 levels and fecal nitrogen excretion in preterm infants.

We measured fecal elastase-1 (FE1) levels in 34 preterm newborns (15 small-for-gestational-age and 19 appropriate-for-gestational-age) during the first 2 months of life and evaluated whether they were correlated with nitrogen loss in stools. FE1 increased over time, and values were similar in both groups of newborns. Fecal nitrogen was significantly higher in small-for-gestational-age infants. There was no correlation between FE1 levels and fecal nitrogen excretion. Pancreatic proteolytic function was efficient at an early stage in enterally fed preterm newborns. Despite the similar FE1 values, fecal nitrogen loss was significantly higher in small-for-gestational-age preterm infants than in appropriate-for-gestational-age preterm infants.