Natural Health News — Breastmilk, which consists of a complex and continually changing blend of proteins, fats and sugars, helps protect babies against bacterial infections. But not in the way most of us thought.
In the past, scientists have concentrated their search for the source of breastmilk’s antibacterial properties on the proteins it contains. But researchers at Vanderbilt University in the US have discovered that some of the carbohydrates in human milk have important antibacterial properties.
“This is the first example of generalised, antimicrobial activity on the part of the carbohydrates in human milk,” said Assistant Professor of Chemistry Steven Townsend, who directed the study. “One of the remarkable properties of these compounds is that they are clearly non-toxic, unlike most antibiotics.”
The results of the investigation were presented at the recent annual meeting of the American Chemical Society in Washington DC and are published in the journal Infectious Diseases.
» Scientists have long believed that the proteins in human breastmilk that are responsible for protecting babies against infection.
» But emerging evidence suggests that unique carbohydrates (sugars) in breastmilk, known as oligosaccharides, may be responsible.
» Tests showed that some of these sugars could kill an entire colony of Strep B bacteria – which is a leading cause of infections in newborns worldwide.
What motivated the research was the growing problem of bacterial resistance to antibiotics, which the Centers for Disease Control and Prevention estimates causes 23,000 deaths annually.
“We started to look for different methods to defeat infectious bacteria. For inspiration, we turned to one particular bacteria, Group B Strep. We wondered whether its common host, pregnant women, produces compounds that can either weaken or kill strep, which is a leading cause of infections in newborns worldwide,” Townsend said.
Instead of searching for proteins in human milk with antimicrobial properties, Townsend and his colleagues turned their attention to the sugars, which are considerably more difficult to study.
“For most of the last century, biochemists have argued that proteins are most important and sugars are an afterthought. Most people have bought into that argument, even though there’s no data to support it,” Townsend said. “Far less is known about the function of sugars and, as a trained glycoprotein chemist, I wanted to explore their role.”
To do so, the researchers collected human milk carbohydrates, also called oligosaccharides, from a number of different donor samples and profiled them with a mass spectrometry technique that can identify thousands of large biomolecules simultaneously. Then they added the compounds to strep cultures and observed the result under the microscope. This showed that not only do some of these oligosaccharides kill the bacteria directly but some also physically break down the biofilms that the bacteria form to protect themselves.
“Our results show that these sugars have a one-two punch,” said Townsend. “First, they sensitise the target bacteria and then they kill them. Biologists sometimes call this ‘synthetic lethality’ and there is a major push to develop new antimicrobial drugs with this capability.”
The carbohydrates in breastmilk, say the researchers can act on their own, but also enhance the effectiveness of the antibacterial proteins also present.
The next step, they say is to identify which of these natural sugars is the most effective. It’s a big ask; breastmilk contains over 200 unique sugars.
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