It is a common notion that breastfeeding your babies is essential to their health, but why does it happen? What sets you apart from other types of milk or infant formula?
The secret may lie in just one compound in which breast milk is rich.
The study, conducted by researchers from the University of Iowa, Mississippi State University and National Jewish Health, was published a few days ago in Nature's Scientific Reports. They conducted several tests on human milk, bovine milk and infant formula for antimicrobial and anti-inflammatory properties, suspecting that a compound called glycerol monolaurate (GML) plays a key role in them.
In addition to milk, GML is also commonly found in coconut milk, dietary supplements and even cosmetics.
Looking at GML measurements, they found that human milk contained approximately twenty times more GML than bovine milk. In addition, no GML was detected in the infant formula.
The antibacterial properties of each milk type have been tested on several commonly found bacteria types: S. aureus, B. subtilis, C. perfringens, E. coli and E. faecalis. Human milk samples have been found to inhibit the growth of all types of bacteria, excluding E. faecaliscompared to bovine milk and infant formula. Human milk was especially effective against B. subtilis, a common type of intestinal bacteria.
The case of E. faecalis Interestingly, neither human milk, bovine milk nor infant formula were able to inhibit its growth. An important difference between this type of bacteria compared to others is that it produces a compound called reutericycline, which is considered an analog (with a similar structure) of GML. What this may mean is that GML may actually be supporting some types of bacterial growth rather than inhibiting it.
To see how much antimicrobial activity GML was contributing, they were removed from human and bovine milk samples and retested in S. aureus samples. Apparently, GML is highly significant, since GML-free human milk did not have the same antimicrobial properties as the previous test, which returned when GML was added back to milk. With the addition of GML, bovine milk was also able to exhibit antimicrobial properties similar to human milk, showing the possible importance of the compound in this type of activity.
They also found that human milk inhibited the production of IL-8, which is responsible for many inflammatory effects, to near-historical levels. This effect was not found in bovine milk or infant formula.
In short, the high amount of GML in human milk can play a critical role in a child's development with its antimicrobial and anti-inflammatory properties. Similarly, the low amount of GML in bovine milk and infant formula had a factor in its failure to produce antimicrobial and anti-inflammatory activity.
Further testing is still needed to determine whether GML additives to bovine milk and infant formula can have beneficial effects.
However, with the results of this study, the case of breastfeeding becomes stronger.