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The probiotic strain, B. infantis, helps babies effectively digest human milk and maintain a healthy microbiome against pathogens
Right from birth and to their first exposure in a new world, babies’ immune systems are naive and vulnerable, learning to distinguish allies from pathogens. That process begins directly from the gut of babies, a whole sub-world of living microbes called the “microbiome.” However, in developed nations over the past few decades, the microbiome of babies has changed for the worse.
Recently, a team of researchers discovered a probiotic called B. infantis that lives up to one year in babies’ digestive tracts, playing a critical role in shaping a healthy microbiome and therefore, a healthy immune system. Jennifer Smilowitz, the leading author in the clinical study and the associate director of the Human Studies Research Program for the Foods for Health Institute at UC Davis, described the role B. infantis plays in breast milk-fed babies.
“Human milk oligosaccharides, or HMOs, are highly abundant in human milk,” Smilowitz said. “They are not digested by humans because we don’t have the enzymes in our gut to digest them. Of all the microbes that do consume them—there’s not too many of them—B. Infantis is like this incredible resource that eats them up. It outperforms all the other microbes and is like the superstar that really only prefers HMOs.”
Because human milk is the sole source of nutrients for babies in their first six months of life, B. infantis is a necessary, beneficial microbe for babies to effectively digest the HMOs and ultimately ensure a healthy microbiome, according to Smilowitz.
Dr. Mark Underwood, who is trained in neonatal medicine and is now a retired general pediatrician from UC Davis, further explained other properties of B. infantis aside from effectively colonizing the intestinal tract of breast milk-fed babies for up to one year.
“B. infantis has other cool properties like decreasing inflammation,” Underwood said. “Another benefit of B. infantis is that it tends to displace the pathogenic bacteria that can cause infection. Those bacteria can’t use human milk as a food source, so they get outcompeted.”
Claire O’Brien, a fourth-year Ph.D. student part of the pharmacology and toxicology graduate group at UC Davis who worked with Smilowitz, describes the significance of the longevity of B. infantis.
“When we think about probiotics, it’s usually really transient, especially in adults,” O’Brien said. “You take a probiotic supplement and that may have some impact on your microbiome and in the very, very short term. After you stop taking them, that effect is pretty much gone immediately, and so the really interesting finding was that, even though these babies had not had a probiotic since they were one month old, we were actually able to see that change in the microbiome persisted for one year out, so that was really a novel kind of finding for this study that I think surprised a lot of the researchers.”
In the same vein as O’Brien’s explanation, Smilowitz provided the analogy of probiotics as campers in a “campsite” that are in constant competition with each other.
“If you take a probiotic, that little bug will likely be in your gut, but after you stop taking them, they will die out because you already have an existing microbiome,” Smilowitz said. “Think about a campsite. All the campsites are taken and there’s no space for the new guys. But for babies, they don’t have filled campsites, so B. infantis can really take traction in a baby.”
As long as B. infantis was provided with its food, HMOs, babies could continue to digest the nutrient effectively. The significant finding of this study, as Smilowitz and her team discovered, was its effective colonization in the gut after one year, even when babies typically start eating solid foods at around six months old and may no longer ingest human milk as a main source of nutrients.
With changes in medical practices, such as a greater increase in C-sections and use of antibiotics and infant formula, as well as changes in diets over time, the natural composition of the microbiomes in babies has shown a large decrease in B. infantis. The supplementation of the probiotic along with human milk has become all the more necessary to restore their microbiomes.
“These babies [in Davis] did not have an abundance of B. infantis, with much lower levels compared to babies from developing nations like Gambia and Bangladesh,” Smilowitz said. “We saw that 30% of the microbiome was represented by B. infantis instead of 80%.”
However, the future of probiotics in shaping and maintaining a child’s microbiome is bright, and Smilowitz highlighted her research’s expansion of this field into later stages of development, like toddlers, and to other areas with microbiomes, such as the mouth.
“Being able to alter and support the infant microbiome was a big finding,” Smilowitz said. “But I am also excited to be looking at different sorts of combinations of foods and microbes to support a healthy microbiome in many parts of the body, with an emphasis on pregnancy and lactation.”
Written by: Brandon Nguyen – firstname.lastname@example.org