Scientists Discover 'Hidden' Gut Bacteria That Could Revolutionize Probiotic Design

Researchers at the University of Cambridge have identified a previously overlooked bacterial group called CAG-170 that appears fundamental to gut health, yet remains stubbornly difficult to culture in laboratories. The discovery, based on analysis of gut samples from over 11,000 people across 39 countries and 13 diseases, suggests that the future of probiotics may depend on understanding microbes we've barely begun to study.

What Makes CAG-170 So Special—and So Elusive?

Healthy people consistently have higher levels of CAG-170 than those with inflammatory bowel disease (IBD) and obesity, making it a potential marker for overall gut health. The bacterial group may support digestion and produce vitamin B12, a nutrient critical for energy and neurological function. Yet here's the catch: researchers have successfully grown only one strain out of more than 300 identified strains to date.

The challenge isn't a lack of effort—it's that CAG-170 bacteria are finicky. They exist at very low levels in the gut, making them hard to isolate using standard laboratory techniques. They're also sensitive to oxygen damage, requiring samples to be processed rapidly. Most critically, they likely have specialized nutritional needs that researchers haven't yet figured out how to replicate in a petri dish.

"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," explains Dr. Alexandre Almeida, research fellow at Cambridge who led the investigation.

Why Should You Care About Bacteria You Can't Even Grow?

The implications are significant for anyone taking probiotics or considering them. Most commercial probiotic supplements rely on well-established strains like Lactobacillus and Bifidobacterium—bacteria that are easy to culture and have decades of research behind them. But if CAG-170 plays a fundamental role in health that these common strains don't fully address, the entire probiotic industry may need to expand its toolkit.

The research suggests that CAG-170 could serve as a health indicator for your gut microbiome, similar to how cholesterol levels indicate heart health. Potential innovations might help maintain healthy levels of this group, though developing such treatments will require solving the cultivation puzzle first.

What Does This Mean for Choosing Gut Health Supplements Today?

While scientists work on next-generation probiotics targeting CAG-170, current supplement strategies remain valuable. When selecting gut health supplements, consider these evidence-based factors:

• Probiotic Strain Specificity: Look for supplements listing exact strain names rather than just genus and species. Different strains serve different purposes—Lactobacillus acidophilus supports lactose digestion, while Bifidobacterium longum helps with immune function.
• Colony Forming Units (CFUs): These measure the number of live bacteria in each dose. Therapeutic doses typically range from 10 billion to 100 billion CFUs, though quality matters more than quantity since bacteria must survive stomach acid to reach your intestines alive.
• Prebiotic Support: Prebiotics are non-digestible fibers that feed your existing beneficial bacteria. Natural sources include garlic, onions, bananas, and asparagus, while supplements may contain inulin, fructooligosaccharides (FOS), or galactooligosaccharides (GOS).
• Third-Party Testing: Verify that supplements contain what their labels claim and remain free from harmful contaminants through certifications from organizations like NSF International or USP.

For specific digestive issues, combining digestive enzymes with targeted probiotic strains often provides faster results than single-ingredient supplements. Taking enzymes 15 to 30 minutes before meals optimizes their effectiveness.

The Bigger Picture: A Paradigm Shift in Probiotic Science

The Cambridge findings represent a fundamental shift in how scientists think about the microbiome. For decades, research focused on the bacteria we could easily study and culture. The discovery that two-thirds of gut bacterial species were previously unknown suggests we've been working with an incomplete picture of human health.

This doesn't mean current probiotics are ineffective—they've helped millions manage digestive issues. Rather, it suggests that next-generation therapeutics will likely incorporate a broader range of bacterial species, including those like CAG-170 that are challenging to work with but potentially essential for optimal health. The probiotic industry faces a significant challenge: developing formulations for bacteria that resist conventional cultivation methods.

Until those innovations arrive, the best approach remains supporting your existing gut bacteria through diverse, whole foods rich in prebiotics, managing stress, getting adequate sleep, and choosing high-quality supplements with proven strains and third-party testing. Your gut microbiome is unique to you, and while CAG-170 may be the next frontier in probiotic science, the fundamentals of gut health—diversity, balance, and consistent support—remain unchanged.