A recent study published in Nature: Communications Biology has revealed a troubling shift in the gut health of infants in the United States. Researchers found that most American babies are missing a key group of beneficial bacteria—an absence that may significantly raise their risk of developing allergies, asthma, and other immune-related conditions later in life. This finding challenges long-held assumptions about how the immune system is shaped during the earliest stages of life.
At the center of this discovery is Bifidobacterium, particularly Bifidobacterium longum infantis. For generations, these bacteria were a defining feature of a healthy infant gut, especially in breastfed babies. Their role is highly specialized: they feed on Human Milk Oligosaccharides (HMOs), unique sugars found in breast milk that infants themselves cannot digest. By breaking down these compounds, Bifidobacterium help create an anti-inflammatory environment that supports proper immune development.
The findings come from the large-scale “My Baby Biome” study, which analyzed stool samples from more than 400 infants across diverse U.S. populations. The results were striking. About 76% of the babies had low levels of Bifidobacterium, and in roughly one out of four infants, these bacteria were completely absent. This was true regardless of whether babies were breastfed or formula-fed, pointing to broader environmental or medical factors influencing early gut colonization.
When Bifidobacterium are missing, other microbes quickly take their place—but not necessarily helpful ones. The study showed that infants lacking these protective bacteria developed gut profiles associated with increased inflammation, antibiotic resistance genes, and potentially harmful microbial activity. This imbalance was especially common in babies born by C-section, who often miss out on early exposure to beneficial maternal microbes.
These microbial shifts are not just theoretical concerns. By following the infants over time, researchers found that babies with low Bifidobacterium levels were nearly three times more likely to develop atopic conditions such as eczema, food allergies, or asthma within their first two years. This strong association highlights how critical early microbial exposure is for “training” the immune system.
One of the strengths of the “My Baby Biome” study lies in its scale and methodology. Using advanced genomic sequencing and metabolic analysis, researchers were able to pinpoint not only which microbes were missing, but also which metabolic pathways were disrupted. This level of detail reinforces the conclusion that the problem is widespread and clinically relevant—not an isolated anomaly.
More importantly, the study offers a path forward. By identifying what is missing in the modern infant gut, it opens the door to targeted interventions, such as infant-specific probiotics or synbiotics that combine beneficial bacteria with HMOs. Supporting healthy gut colonization early in life may become a powerful strategy to reduce the risk of chronic inflammatory and allergic diseases and to promote better long-term health.
SOURCE: Nature
Add comment
Comments