Developing babies with changing physiologic requirements need the adjustment that takes place in the levels of nitrite and nitrate in breast milk in the early days after birth.
The University of Texas Health Science Centre has shown the essential nature of nitrite in breast milk.
"While the nitrite and nitrate composition of breast milk has been reported, this is the first study to demonstrate the changing levels of nitrite and nitrate early on," said Nathan Bryan, the study's senior author.
The scientists measured nitrite and nitrate levels in breast milk during the first three days of birth (colostrum), days three to seven (transition milk) and eight or more days (mature milk).
Seventy-nine patient samples were analysed.
Bryan said colostrum has significantly higher concentrations of nitrite and significantly lower concentrations of nitrate than both transition and mature milk, which he believes may be nature's way of providing nitric oxide to the newborns whose gastrointestinal tract is not yet colonized by bacteria that convert nitrate to nitrite.
To corroborate their findings, researchers analysed milk samples taken from two women on 14 consecutive days and the scientists observed the same change in the nitrite and nitrate levels.
The investigators also measured the level of dietary nitrite and nitrate in alternative sources of newborn nutrition: formula, cow milk and soy milk.
Noting that breast milk is considered more beneficial to newborns than these others sources of nutrition, the study revealed that colostrum contains the highest amount of nitrite of any of the milk products tested.
The study was published in Breastfeeding Medicine, the official journal of the Academy of Breastfeeding Medicine.