Infants in Western countries – the US, UK, and Sweden – develop gut microbiomes significantly different from those in South Asia and sub-Saharan Africa, with a critical bacterial species, Bifidobacterium longum infantis, being almost entirely absent in Western babies. This finding, revealed by a global study sequencing over 1900 bacterial genomes, underscores how early gut colonization impacts long-term health and highlights the need for regionally tailored probiotics.
The First 1000 Days: A Microbiome Foundation
The first two years of life are a critical period for establishing a healthy gut microbiome. This microbial ecosystem influences immune function, mental health, and susceptibility to chronic diseases. Until now, research has heavily focused on Western infants, leaving a major gap in understanding global microbiome diversity. The study by Yan Shao and colleagues at the Wellcome Sanger Institute fills this void by comparing samples from the UK, Sweden, US, and seven countries in South Asia and Africa.
Key Differences: Infantis vs. Longum
Researchers discovered a stark divergence in bacterial presence. Roughly 70% of infants in African and South Asian countries had B. longum infantis established in their guts by two months, compared to fewer than 2% in Western babies. Conversely, B. longum longum was common in Western infants (around 33% prevalence by two months) but rare in the African and Asian groups (less than 10%).
These findings suggest a geographic split in bacterial dominance, with infantis thriving in some regions while longum dominates others.
Why Does This Matter? Diet and Adaptation
The difference likely stems from maternal diets. Bifidobacteria aid in breast milk digestion, and the composition of milk varies by region. Longum longum may be better suited to Western diets, while infantis thrives where other dietary patterns prevail. Regardless, infants lacking either species usually harbor similar bacteria like Bifidobacterium breve.
Tailoring Probiotics for Maximum Impact
The study dramatically increases available genomic data for South Asian (17x increase ) and African (11x increase ) bacterial strains. This has major implications for probiotic development, particularly for premature infants. Probiotics are not broadly recommended for full-term babies, but they are sometimes given to those born prematurely. Now, it’s possible to create probiotics specifically suited for a baby’s region, maximizing their chances of successful colonization. A B. longum infantis probiotic may work well in Africa and Asia but struggle to establish itself in a Western gut, and vice versa.
This research proves that a one-size-fits-all approach to infant gut health is insufficient. To optimize probiotic effectiveness, we must understand how bacterial communities differ across the world.
