Summary: Glycerol monolaurate (GML), a natural compound present in human breast milk, helps suppress harmful bacteria while supporting beneficial microbes and reducing inflammation in epithelial cells. Researchers suggest GML could be a low-cost additive for cow’s milk and infant formula to better protect infants from bacterial and viral gut infections.
Source: National Jewish Health
Researchers at National Jewish Health and the University of Iowa have identified glycerol monolaurate (GML) as a key antimicrobial and anti-inflammatory component in human breast milk. The teams found much higher levels of GML in human milk than in bovine milk, and none in the infant formula samples tested. Because GML is inexpensive to produce and selectively targets pathogenic bacteria while sparing beneficial species, the researchers propose further study of GML as a potential additive to cow’s milk and infant formula to improve infant health worldwide.
“Our findings demonstrate that high levels of GML are unique to human breast milk and strongly inhibit growth of pathogenic bacteria,” said Donald Leung, MD, PhD, professor of pediatrics at National Jewish Health and senior author on the published paper.
“While antibiotics can fight bacterial infections in infants, they also eliminate beneficial bacteria,” said Patrick Schlievert, PhD, professor of microbiology and immunology at the University of Iowa Carver College of Medicine and the study’s first author. “GML is much more selective, reducing pathogenic bacteria while allowing helpful bacteria to persist. This selective activity makes GML a promising candidate for improving the safety and nutrition of bovine milk and infant formula.”
The research team measured GML and found it to be substantially elevated in human breast milk compared with bovine milk and absent from the infant formulas they analyzed. In laboratory tests, human milk limited growth of several common pathogens, including Staphylococcus aureus, Bacillus subtilis and Clostridium perfringens, while leaving beneficial bacteria such as Enterococcus faecalis unaffected. Babies fed human milk typically carry higher levels of beneficial Bifidobacterium, Lactobacillus and Enterococcus species, which contribute to gut health and immune development.
When the researchers removed GML and similar lipophilic components from human milk, its antimicrobial activity against S. aureus was lost. Reintroducing purified GML restored that activity. Likewise, adding GML to bovine milk produced measurable antimicrobial effects in the same assays, demonstrating the compound’s direct contribution to the milk’s protective properties.
Beyond its antimicrobial actions, the team found that GML suppressed inflammatory responses in epithelial cells that line the gut and other mucosal surfaces. Controlled inflammation is essential for maintaining barrier function; excessive inflammation can damage epithelial tissue and increase vulnerability to both bacterial and viral infections. By reducing epithelial inflammation, GML may help protect infants from a broader range of infectious insults.
Drs. Schlievert and Leung have applied for a patent covering the use of GML as an additive for cow’s milk and infant formula. Additional studies will be needed to evaluate safety, optimal dosing, stability during processing, and clinical benefits in infants before any product changes are recommended.
Source:
National Jewish Health
Media Contacts:
William Allstetter – National Jewish Health
Image Source:
The image is adapted from the National Jewish Health news release.
Original Research: Open access
“Glycerol Monolaurate Contributes to the Antimicrobial and Anti-inflammatory Activity of Human Milk”. Patrick M. Schlievert, Samuel H. Kilgore, Keun Seok Seo & Donald Y. M. Leung. Scientific Reports. DOI: 10.1038/s41598-019-51130-y.
Abstract (summary)
Human milk contains antimicrobial and immunomodulatory components. The investigators compared glycerol monolaurate (GML) levels and related antimicrobial and anti-inflammatory activity in human milk, bovine milk and infant formula. Human milk contained a substantially higher concentration of GML versus bovine milk, and formula samples contained no detectable GML. For the bacteria tested—Staphylococcus aureus, Bacillus subtilis, Clostridium perfringens and Escherichia coli—human milk showed greater antimicrobial activity than bovine milk or formula, except that Enterococcus faecalis was not inhibited. Ethanol extraction that removed GML and other lipophilic molecules eliminated antibacterial activity in human milk; adding back GML restored activity. GML addition made bovine milk antimicrobial. Human milk, but not bovine milk or formula, inhibited epithelial cell IL-8 production induced by superantigen and bacterial stimuli, consistent with anti-inflammatory effects. These results indicate that GML contributes to the antimicrobial and anti-inflammatory properties of human milk.