ScienceDaily (May 14, 2012) - A new University of Illinois study shows that human
milk oligosaccharides, or HMO, produce short-chain fatty acids that feed a beneficial
microbial population in the infant gut. Not only that, the bacterial composition adjusts
as the baby grows older and his needs change.
Even though 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're virtually absent from infant formula. The scientists
wanted to find out what formula-fed babies were missing.
"We refer to HMO as the fiber of human milk because we don't
have the enzymes to break down these compounds. They pass into the large intestine where
the bacteria digest them.
"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 Sharon Donovan, the U of I's Melissa M.
Noel Endowed Professor in Nutrition and Health.
With this study, Donovan is gaining insight into the mystery. For
the first time, scientists have shown that a complex mixture of HMO and a single HMO
component produce patterns of short-chain fatty acids that change as the infant gets
A healthy microbiome has both short- and long-term effects on an
infant's health. In the short term, beneficial bacteria protect the infant from
infection by harmful bacteria. In the long term, beneficial bacteria strengthen the
immune system so that it can fend off chronic health problems like food allergies and
asthma, she said.
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.
The colon bacteria were added to test tubes containing HMO and two
prebiotics commonly used in infant formulas. These mixtures were allowed to ferment and
then sampled to see how the bacterial population was 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. 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.
Further, different HMOs produced different patterns of short-chain
fatty acids, and the composition of bacteria in the gut changed over time. "It was
distinctly different at 9 vs. 17 days, making it likely that the functions of HMO change
as the human infant gets older," she said.
According to Donovan, HMO 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," she said.
Funding was provided by a grant from the National Institutes of