Scientists are learning that the trillions of bacteria living in your gut — your gut microbiota — play a huge role in whether you get sick and how sick you get. A recent scientific review focused on a very common digestive condition called diverticular disease (DD), which affects millions of people, especially older adults in developed countries.
First: What Is Diverticular Disease?
Before diving into the bacteria, it helps to understand the condition. Diverticulosis is when small pouches (called diverticula) form in weak spots of the colon wall. Most people who have it don’t even know — it’s often harmless. But in some cases, it becomes symptomatic or inflamed.
The researchers describe three stages of how this condition can develop:
- Diverticulosis — asymptomatic, no inflammation. Just the pouches.
- SUDD (Symptomatic Uncomplicated Diverticular Disease) — symptoms like pain and bloating, but no acute inflammation.
- Acute Diverticulitis (AD) — active, painful inflammation of the diverticula. This is the serious stage that often leads to antibiotic use or hospitalization.
“Diverticulosis is mostly an asymptomatic condition but may become symptomatic in about 20% of cases, causing so-called diverticular disease.”
Key Finding #1: Gut Bacteria Change as the Disease Gets Worse
One of the most important things this review found is that gut bacteria composition seems to shift depending on how severe the disease is. But here’s what’s interesting: simply having diverticulosis (the pouches) doesn’t seem to significantly alter your gut bacteria. So gut bacteria and diverticulitis is related.
“Two studies analyzing the mucosa-associated microbiota failed to find any significant alteration in these patients [with diverticulosis].”
It’s only when symptoms appear — in SUDD and especially acute diverticulitis — that the microbial balance starts looking different. Specifically, the researchers found that certain “good” bacteria that reduce inflammation (like Clostridium cluster IV and Lactobacillaceae) tend to decrease, while other species shift in complex ways.
“The main finding is that not only are some anti-inflammatory and immuno-regulatory taxa such as Clostridium cluster IV and Lactobacillaceae decreased, but also that some species with the same activity, such as A. muciniphila and Roseburia, are increased.”
Key Finding #2: This Isn’t the Same as IBD
You might have heard of inflammatory bowel disease (IBD) — conditions like Crohn’s disease or ulcerative colitis. Because diverticular disease also causes colon inflammation, scientists originally thought the gut bacteria patterns would look similar. They don’t.
The researchers compare the two diseases throughout the article and find important differences. For example, a bacterium called Akkermansia muciniphila tends to be reduced in IBD, but it’s actually elevated in diverticular disease patients. This tells scientists that the two conditions work differently at the bacterial level, which matters for treatment.
This is a different than the connection of gut bacteria to diverticulitis
“These dysbiotic landmarks seem to differ from those typically seen during chronic intestinal inflammation, such as in IBD.”
Key Finding #3: Diet, Age, and Medications All Play a Role
The review explores several reasons why gut bacteria and diverticulitis might differ between patients. Three factors stand out:
Age
Diverticular disease is more common in older adults, and aging itself changes gut bacteria. As we get older, our microbiome becomes less diverse and more vulnerable to disruption.
“Aging is associated with reduced biodiversity of the GM and increased inter-individual variability.”
Diet
Low-fiber, high-red-meat diets — which are associated with a higher risk of diverticulosis — also change which bacteria thrive in the gut. High-fiber diets support the growth of helpful bacterial species, while low-fiber diets do the opposite.
“In contrast, the habitual human consumption of a low-fiber diet leads to a depletion of Clostridia, Actinobacteria, and all butyrate-producing taxa.”
Polypharmacy
Many older adults take multiple medications at the same time (called polypharmacy). This, too, can disrupt gut bacteria — especially drugs that affect gut movement.
“Polypharmacy is linked with intestinal dysbiosis, mainly when drugs, such as opioids and neuroleptics, influence colonic motility.”
Key Finding #4: Probiotics May Help — Possibly Instead of Antibiotics
This is where the research gets especially exciting for those interested in avoiding antibiotic overuse. The article reviews several clinical trials testing probiotics (live beneficial bacteria) as a treatment for diverticular disease — and the results are promising.
In one double-blind, randomized trial of patients with acute uncomplicated diverticulitis (the painful inflammatory stage), patients treated with the probiotic Lactobacillus reuteri — without standard antibiotics — showed meaningful improvements:
“The CRP value and the fecal calprotectin levels were significantly decreased in the probiotic group vs. the placebo group. Finally, the placebo group had a more extended hospital stay than the probiotic group (83.5 h vs. 75.5 h).”
CRP and fecal calprotectin are both markers of inflammation — so lower values mean less inflammation. The fact that probiotic-only patients had shorter hospital stays is a meaningful clinical result.
In another trial focused on preventing recurrence of symptoms (SUDD), both the antibiotic-adjacent drug mesalazine and the probiotic L. casei outperformed placebo:
“Both mesalazine and L. casei, alone or in combination, were significantly better than the placebo in preventing the occurrence of acute diverticulitis.”
The rationale for using probiotics instead of (or alongside) antibiotics comes down to restoring the microbial balance that disease disrupts. Probiotics can:
— Produce natural antimicrobials
— Compete with harmful bacteria
— Reduce pro-inflammatory signals
— Strengthen the gut’s mucosal lining
What Are the Limits of This Research?
The authors are careful to point out that the field is still young. Most studies on gut bacteria and diverticulitis have been small, used different methods for measuring bacteria, and looked at different patient populations. This makes it hard to draw firm conclusions.
“Current studies on the GM composition in DD still suffer from several biases (in particular, different sampling modalities and various microbiota searching techniques). Further studies are needed to confirm whether the currently detected imbalance in the GM is a cause or effect of the different clinical expressions of DD.”
In other words: we don’t yet know whether the bacterial changes cause the disease, or whether the disease causes the bacterial changes. That’s a big open question.
The Big Takeaways
- Gut bacteria matter for diverticular disease — but the relationship is complex and different from other gut diseases like IBD.
- The worse the disease gets, the more the microbial balance shifts — especially a decrease in anti-inflammatory bacteria.
- Diet, age, and medications all influence which bacteria thrive in your gut.
- Probiotics show real promise as a way to treat — and possibly prevent — recurrence of diverticulitis without relying solely on antibiotics.
- More large-scale, standardized research is needed before we can say definitively what role bacteria play and how best to treat the disease through the microbiome.
