The study – published in the Journal of Nutrition – reveals that the breast milk ingredient produces short-chain fatty acids when digested by bacteria in the infant gut. The team says the short-chain fatty acids then feed the population of beneficial microbes in the infant gut.
In addition, the researchers, led by Professor Sharon Donovan from the University of Illinois, USA, show that the bacterial composition of the infant gut adjusts as the baby grows older and its needs change.
Donovan and her team noted that even though human milk oligosaccharides (HMO) are a major component of human milk – present in higher concentration than protein – many of their actions in the infant are not well understood. Furthermore, they noted that the component is virtually absent from infant formula. The researchers said they wanted to find out what formula-fed babies were missing.
"We're curious about the role they play in the development of the breast-fed infant's gut bacteria because the bacteria found in the guts of formula-fed infants is different," said Donovan.
She added that the oligosaccharides are ‘critically important’ in understanding how breastfeeding protects babies.
“Several companies are now able to synthesize HMO, and in the future, we may be able to use them to improve infant formula. There’s evidence that these compounds can bind to receptors on immune cells and, to our knowledge, no current prebiotic ingredient can do that.”
In the study, breast milk was obtained from mothers of preterm infants at Chicago’s Rush University Medical Center, and the HMO were isolated and analyzed. The scientists tested bacteria from 9- and 17-day-old sow-reared and formula-fed piglets – because piglets grow so rapidly, these ages reflect approximately three- and six-month-old human infants, said the authors.
The colon bacteria were added to test tubes containing human milk oligosaccharides (HMO) and two prebiotics commonly used in infant formulas. The mixtures were then allowed to ferment before samples were taken in order to measure how the bacterial populations were changing over time, and what products were being produced by the bacteria.
“When the HMOs were introduced, the bacteria produced short-chain fatty acids, at some cases at higher levels than other prebiotics now used in infant formula,” explained Donovan.
“The short-chain fatty acids can be used as a fuel source for beneficial bacteria and also affect gastrointestinal development and pH in the gut, which reduces the number of disease-causing pathogens,” she said
Furthermore, different HMOs produced different patterns of short-chain fatty acids, while and the composition of bacteria in the gut changed over time, she revealed.
“It was distinctly different at 9 versus 17 days, making it likely that the functions of HMO change as the human infant gets older,” said Donovan.
Source: Journal of Nutrition
Volume 142 Number 4, Pages 681-689, doi: 10.3945/jn.111.154427
“Microbial Composition and In Vitro Fermentation Patterns of Human Milk Oligosaccharides and Prebiotics Differ between Formula-Fed and Sow-Reared Piglets”
Authors: M. Li, L. L. Bauer, X. Chen, M. Wang, T. B. Kuhlenschmidt, M. S. Kuhlenschmidt, G. C. Fahey, S. M. Donovan.