“The REMEDI study shows that it’s not too late to restore a healthy gut microbiome in breastfed infants. B. infantis can successfully take hold even after the newborn period,” said corresponding study author Jennifer Smilowitz, Ph.D., assistant professor of Cooperative Extension in the Department of Nutrition, University of California, Davis.
A healthy early-life gut microbiome is linked to gut health, immune education and development, and overall infant health. Unlike many probiotics, B. infantis is uniquely adapted to thrive on human milk oligosaccharides, the natural sugars found in breast milk, allowing it to persist rather than simply pass through the gut.
The researchers conducted the REMEDI study to test whether the benefits they had previously observed in a study on newborns fed B. infantis alongside human milk could be replicated in older, exclusively breastfed infants with more established gut microbiomes that could potentially be resistant to changes.
The researchers tested how different doses of the B. infantis probiotic (high, medium and low, as well as a placebo) impacted the gut bacteria of exclusively breastfed infants. The infants provided stool samples before, during and after taking the supplement, and the researchers analyzed these to see how their microbiomes responded. The researchers tested whether lower doses of B. infantis, which are commercially available, produced similar effects as the newborn study which used a high dose of the B. infantis probiotic.
The researchers found that B. infantis could successfully increase beneficial gut bacteria in older, exclusively breastfed infants, even after the newborn period. All doses tested worked, and the beneficial bacteria remained present even after supplementation stopped.
“These findings suggest that B. infantis supplementation can restore the infant gut even past the newborn stage,” Smilowitz said. “Unlike many probiotics that disappear once supplementation stops, B. infantis was able to take hold and remain in the gut when paired with human milk, which naturally contains the human milk oligosaccharides it needs to grow. This means even short-term supplementation at a range of doses may have lasting benefits for breastfed infants. The finding that all tested doses were effective suggests this approach may be adaptable to real-world settings where access, timing or dose can vary.”
Reference:
O'Brien CE, Frese SA, Cernioglo K, Damian-Medina K, Mitchell RD, Casaburi G, Melnyk RA, Henrick BM, Smilowitz JT. 0. Randomized, placebo-controlled trial reveals the impact of dose and timing of Bifidobacterium infantis probiotic supplementation on breastfed infants’ gut microbiome. mSphere 0:e00518-25. https://doi.org/10.1128/msphere.00518-25
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