Non-enzymatic nitric oxide generation in the stomachs of breastfed neonates

Human breast milk contains high concentrations of nitrate and nitrite in the early postpartum period. The acidification of nitrite leads to the generation of nitric oxide (NO) in the gastric lumen. NO reportedly plays an important role in adult stomachs. The objective of the present study was to determine whether NO is generated in the stomach of breastfed neonates. We examined (i) the concentrations of nitrite and nitrate in human breast milk and formula milk, according to the method based on the Griess reaction; (ii) the concentration of NO in gases collected from the lumen of the neonatal stomach; and (iii) NO generation in acidified milks in vitro, using a NO chemiluminescence analyser. We found that breast milk contained high levels of nitrite, the NO level in the stomach gas of neonates fed only breast milk peaked on days 2 to 5, and NO was present on the milk surface in vitro. These findings suggest that a high concentration of nitrite in the stomachs of breastfed neonates enables a high production of NO. We propose that breast milk is important in regulating the mucosal blood flow and gastric motility and in achieving bacteriostasis via induction of NO generation in the neonatal stomach.