Partition of nitrogen intake and excretion in low-birth-weight infants
S. M. Donovan, S. A. Atkinson, R. K. Whyte and B. Lonnerdal
Department of Nutrition, University of California, Davis 95616.
Although nitrogen balance studies have been carried out in low-birth-weight
infants, few have partitioned the nitrogen into its components. In this
study, 72-hour balance studies were conducted in 24 low-birth-weight
infants (gestational age, 30.7 +/- 1.6 weeks; birth weight 1.36 +/- 0.25
kg) fed their mothers' milk (preterm milk) or 50% preterm milk and 50%
formula. Total nitrogen, nonprotein nitrogen, and whey protein intake and
excretion were measured. Total nitrogen intake (preterm milk group, 452 +/-
138 mg/kg per day; preterm + formula group, 406 +/- 93 mg/kg per day),
absorption (85%), and retention (71%) were not significantly different
between groups. Intact and fragments of secretory IgA and lactoferrin were
detected in soluble fecal extracts, and represented 25% and 9% of intake,
respectively. Feeding preterm milk allows for nitrogen accretion similar to
intrauterine growth rates for 5 weeks postnatally, and provides potentially
functional proteins for the low-birth-weight infant.
