If you’ve been diagnosed with diverticulosis or diverticulitis, you’re not alone. This condition is more common than many realize, especially among older adults. However, what’s truly revealing is not just its frequency, but how little we discuss its connection with the gut microbiome.
This text doesn’t propose an alternative theory, but rather an invitation to view what we already know through a new lens: the communities of microorganisms that inhabit our intestines. Because when we understand how these microscopic residents live and behave, we also begin to understand why we get sick and how we might stop it.
A Common Disease… Poorly Understood?
Diverticular disease is divided into two categories: diverticulosis (when pouches form in the colon without symptoms) and diverticulitis (when those pouches become inflamed or infected). It’s so common that more than 50% of people over 60 in the U.S. have it, and up to two-thirds of adults over 70.
Most people are asymptomatic, but around 20% will develop diverticulitis, and 5 to 10% will progress to complicated cases involving abscesses, fistulas, obstructions, or perforations.
How do we go from a silent condition to a potentially severe one? The answers offered by the microbiome are both unsettling and illuminating.
Genes to Blame? Not Quite
While genetics can play a role, its impact is relatively small, under 10% in most chronic diseases. The concerning fact is that while our genes aren’t changing, both the prevalence and severity of diverticulitis are increasing. Something else is driving this trend.
One of the most consistent risk factors is chronic constipation, which not only precedes diverticulitis but also neurodegenerative diseases like Parkinson’s. From the microbiome perspective, constipation becomes a clear warning sign: a gut in dysbiosis.
Lifestyle, Inflammation, and Opportunistic Bacteria
Factors like sedentary behavior, obesity, red meat consumption, smoking, prolonged NSAID use, and low fiber intake are strongly linked to diverticulitis. These not only impact gut function but actively shape the microbiome, encouraging pro-inflammatory communities dominated by opportunistic bacteria.
One bacterial family consistently associated with diverticulitis is Enterobacteriaceae, including familiar names like E. coli, Klebsiella pneumoniae, and Enterobacter aerogenes. These species are significantly more abundant in people with acute diverticulitis than in healthy controls. They are the hallmark of a disrupted, inflamed ecosystem.
The Diversity Paradox
It’s often said that microbial diversity is a sign of health. But it’s not that simple. Some studies show that patients with diverticulitis have higher microbial diversity than healthy individuals.
How is that possible? Because diversity isn’t always a good thing, especially when it includes many harmful players. The quality of microbial species matters as much as quantity. A high-diversity ecosystem can still be dominated by pro-inflammatory actors.
The Good Guys Have Names Too
On the healthier end of the microbial spectrum, butyrate-producing bacteria, which help regulate inflammation and support intestinal integrity, are consistently more abundant in healthy individuals. These include Faecalibacterium prausnitzii, Eubacterium, Alistipes, and Oscillibacter.
The contrast is striking: those with diverticulitis show higher levels of inflammation-linked bacteria like Ruminococcus gnavus, Eggerthella lenta, and various Clostridium species.
PPIs, Antibiotics, and Invisible Damage
Among modifiable risk factors, proton pump inhibitors (PPIs) stand out. By reducing stomach acid, they allow microbes that would normally be destroyed to pass into the intestine. They also impair protein digestion, leaving more substrate for fermentation by harmful gut microbes.
Yet, the most damaging factor remains excessive antibiotic use. These don’t just kill pathogens, they can irreversibly alter the ecological balance of the gut. In a study of over 29,000 women, past antibiotic use was independently associated with a higher risk of acute diverticulitis.
Rebuilding the Ecosystem Instead of Fighting the Invaders
A clinical case illustrates this shift in paradigm. A woman with over a decade of recurrent, multifocal diverticulitis, treated with multiple surgeries and courses of antibiotics, underwent a fecal microbiota transplant (FMT). After the procedure, she remained recurrence-free for at least 20 months.
The lesson is not that everyone needs an FMT. Rather, it’s that the goal is to change the environment, not just attack specific microbes. Supporting beneficial species that have been marginalized allows the ecosystem to rebalance itself. Repeated antibiotic cycles or natural antimicrobials, without restoring ecological health, often lead to the same relapses.
Conclusion
The evidence reviewed around diverticulitis and the microbiome reveals a pattern repeated in many digestive conditions: a shift in microbial composition toward pro-inflammatory communities, largely driven by modifiable factors like antibiotic use, PPIs, chronic constipation, and dietary patterns.
Beyond this specific condition, the microbiome-centered approach offers a more accurate and functional lens for understanding intestinal inflammation, its triggers, and the realistic ways we might intervene not by force, but by redesigning the ecosystem itself.