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Study further understanding of critical ingredients
In a study published online on Oct. 19 in advance of print in Breastfeeding Medicine, the official journal of the Academy of Breastfeeding Medicine, researchers at The University of Texas Health Science Center at Houston (UTHealth) announced the results of an observational study showing that the levels of nitrite and nitrate in breast milk change during the initial days after birth, which the scientists argue is to accommodate the changing physiologic requirements of developing babies.
"This research shows the essential nature of nitrite in breast milk," said Nathan Bryan, Ph.D., the study's senior author and an assistant professor at the UTHealth Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases (IMM). "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."
Dietary nitrite and nitrate are part of a normal diet. When people eat nitrate-rich vegetables, the bacteria in their mouths and stomachs converts the nitrate into nitrite, which in turn aids in the production of nitric oxide. Nitric oxide keeps blood pressure levels normal, fights infection and supports the nervous system. Animal studies suggest nitric oxide might even guard against heart attack and stroke.
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 analyzed and they were donated by mothers who were either admitted to Memorial Hermann -- Texas Medical Center (TMC) in Houston for childbirth or who were visiting a UT Physicians' clinic in the TMC.
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. Nitrite-rich colostrum overcomes this deficit, he said.
Human milk concentrations of colostrum, transition milk and mature milk were 0.08 mg/100ml nitrite and 0.19 mg/100ml nitrate, 0.001 mg/100ml nitrite and 0.52 mg/100ml nitrate, and 0.001 mg/100ml nitrite and 0.3 mg/100ml nitrate, respectively.
To corroborate their findings, researchers analyzed milk samples taken from two women on 14 consecutive days and the scientists observed the same change in the nitrite and nitrate levels.
Some women cannot nurse their children due to health issues. Other women may choose not to breastfeed so 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, Bryan said the study revealed that colostrum contains the highest amount of nitrite of any of the milk products tested.