A previously unknown group of gut bacteria could become a powerful marker of overall health, according to groundbreaking research from the University of Cambridge published in Cell Host & Microbe.
The bacteria group, known as CAG-170, was consistently found at higher levels in healthy individuals across an analysis of more than 11,000 people from 39 countries. People with chronic conditions—from inflammatory bowel disease to obesity to chronic fatigue syndrome—had significantly lower levels.
What Makes CAG-170 Special?
CAG-170 belongs to what scientists call the "hidden microbiome"—bacteria that exist in our guts but have never been successfully grown in laboratory conditions. Until now, studying them was nearly impossible.
Using advanced computational techniques and metagenomic analysis, the Cambridge team identified CAG-170's unique genetic fingerprint and searched for it across thousands of gut microbiome samples.
What they found was striking: CAG-170 wasn't just present in healthy people—it was consistently one of the strongest predictors of overall gut health across diverse populations worldwide.
Vitamin B12 Production and Digestive Support
Genetic analysis revealed that CAG-170 bacteria have two important capabilities:
- Vitamin B12 production — These bacteria can produce large quantities of B12
- Carbohydrate breakdown — They carry enzymes that help digest sugars, fibers, and complex carbohydrates
Interestingly, researchers believe the B12 produced by CAG-170 primarily supports other beneficial gut bacteria rather than directly benefiting the human host. Think of CAG-170 as a "keystone species" that helps maintain balance in the broader gut ecosystem.
The Hidden Microbiome: 3,000+ Unknown Species
This discovery builds on earlier work by Dr. Alexandre Almeida, who created the Unified Human Gastrointestinal Genome catalogue—a comprehensive reference library mapping the genetic blueprints of gut microbes.
That research identified over 4,600 bacterial species living in the human gut. Remarkably, more than 3,000 of these had never been documented before.
"Our earlier work revealed that around two-thirds of the species in our gut microbiome were previously unknown. No-one knew what they were doing there—and now we've found that some of these are a fundamental and underappreciated component of human health." — Dr. Alexandre Almeida, University of Cambridge
Three Independent Analyses, Same Result
The link between CAG-170 and health wasn't a fluke. The research team confirmed it through three separate analyses:
Disease comparison — Across 13 different diseases including Crohn's, colorectal cancer, Parkinson's, and multiple sclerosis, CAG-170 levels were consistently lower than in healthy individuals
Ecosystem stability — When analyzing 6,000+ healthy people, CAG-170 ranked as the bacterial group most associated with stable, balanced gut ecosystems
Dysbiosis connection — People with imbalanced gut microbiomes (dysbiosis) showed lower CAG-170 levels, linking the bacteria to conditions like IBS, rheumatoid arthritis, and even anxiety and depression
Future Implications: Next-Generation Probiotics
The probiotic industry has largely relied on the same bacterial species for decades—typically Lactobacillus and Bifidobacterium strains that can be easily cultured in labs.
But this research suggests we've been missing an entire category of beneficial bacteria.
"The probiotic industry hasn't really kept up with gut microbiome research—people are still using the same probiotic species that were being used decades ago. We're now discovering new groups of bacteria like CAG-170 with important links to our health, and probiotics aimed at supporting them could have a much greater health benefit." — Dr. Alexandre Almeida
The challenge? Most CAG-170 bacteria can't yet be grown outside the human gut. Scientists will need to develop new cultivation methods before these findings can translate into actual probiotic products.
What This Means For You
While CAG-170 probiotics aren't available yet, this research reinforces several established gut health principles:
- Bacterial diversity matters — The healthiest guts have a wide variety of species, including many we're only beginning to discover
- Diet feeds your microbiome — Since CAG-170 helps break down carbohydrates and fibers, a fiber-rich diet likely supports these beneficial bacteria
- "Hidden" bacteria are important — Standard probiotics only scratch the surface of what a healthy microbiome actually looks like
As research techniques improve, expect to see more discoveries from the hidden microbiome—and potentially a new generation of probiotics designed around these previously unknown beneficial species.
Source: Almeida, A. et al. (2026). "Hidden gut bacteria CAG-170 associated with human health." Cell Host & Microbe. University of Cambridge.
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