Dysbiosis: Can an unbalanced gut microbiome cause inflammation?

• Dysbiosis is an imbalance in the gut microbiome, often characterized by a loss of diversity or a shift in the balance of helpful to harmful bacteria.

• Research suggests dysbiosis can contribute to chronic, low-grade inflammation, which is linked to a wide range of health conditions.

• The relationship runs both ways: Inflammation can also disrupt the gut microbiome, creating a cycle that's hard to break.

• Diet is one of the main things we can change to help restore balance in our microbiome and reduce inflammation.

Your gut microbiome is a complex ecosystem that hosts trillions of microbes (bacteria, fungi, viruses, and more). 

A healthy microbiome tends to be diverse, with a wide range of species that help us handle different foods, environments, and challenges, and with helpful microbes outnumbering the unhelpful ones.

One question researchers are especially interested in is whether dysbiosis can drive inflammation, and what that might mean for our health over time.

Here, we'll look at what dysbiosis is, how it may fuel inflammation, and what you can do to restore balance.

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What is dysbiosis?

Dysbiosis refers to an imbalance in your gut microbial community. It's not a single, well-defined diagnosis, but more of an umbrella term for a range of disruptions, including:

• a loss of microbial diversity

• an overgrowth of potentially harmful microbes

• a reduction in beneficial species

Your microbiome is shaped by many factors, including what you eat, medications such as antibiotics, how you were born, whether you were breast- or bottle-fed, stress levels, environment, and sleep quality. 

All of these can tip the balance toward or away from dysbiosis.

What is inflammation?

Inflammation isn't inherently bad. It's actually your body's defense system at work. 

When you're injured or fighting an infection, your immune system triggers a short burst of inflammation to protect and repair you, then settles down again once the threat has passed.

Over time, this kind of inflammation has been linked to conditions like cardiovascular disease, type 2 diabetes, autoimmune conditions, some cancers, and depression.

Can dysbiosis cause inflammation?

The short answer is yes: Dysbiosis can cause and perpetuate inflammation. This is a constantly evolving field of research, and multiple complex mechanisms are involved. 

Next, we’ll walk through just some of these key mechanisms:

Reduced SCFA production

Among the most important products of a healthy gut microbiome are short-chain fatty acids (SCFAs). These are small molecules produced when beneficial bacteria ferment dietary fiber. 

When dysbiosis occurs, many of the beneficial bacteria that produce SCFAs are depleted.

This means fewer SCFAs are produced, and because they help maintain both the gut barrier and the immune system, their decline has knock-on effects throughout the body.

An overgrowth of harmful microbes

Dysbiosis isn't just about losing beneficial bacteria; it also involves the expansion of harmful ones. 

When the balance tips, opportunistic and potentially harmful species can flourish in the space left behind. 

These organisms can produce toxins and pro-inflammatory molecules that directly irritate the gut lining and stimulate immune responses.

A weakened gut barrier

Your gut lining acts as a selective barrier, letting nutrients into the bloodstream while keeping harmful substances out. 

The immune system recognizes these as foreign and mounts an inflammatory response. This is one of the key ways dysbiosis can trigger low-grade, body-wide inflammation.

Shifts in immune regulation

Around 70% of your immune cells reside in your gut, and they're in constant communication with your microbiome.

Beneficial microbes and the SCFAs they produce help train the immune system to tolerate harmless substances (like food) and respond appropriately to genuine threats. 

When the microbiome becomes disrupted, that calibration goes wrong. Regulatory immune cells decline, pro-inflammatory cells become more active, and the immune system shifts toward a state of chronic over-activation.

A two-way street

Just as dysbiosis can drive inflammation, inflammation can reshape the gut environment to favor harmful microbes over beneficial ones, altering oxygen balance and pH and thinning the protective mucus layer.

Because each side feeds the other, most research now focuses on breaking the cycle rather than treating one end in isolation.

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What can you do?

The good news is that both the gut microbiome and inflammation are remarkably responsive to diet and lifestyle changes. 

And because the two are so tightly linked, the same core habits tend to help both at once, supporting your microbiome and calming inflammation, rather than tackling each in isolation.

Here’s what to do:

1. Eat more fiber

Fiber is the primary fuel for beneficial gut bacteria, and most of us only eat about half as much as we should. 

Foods like legumes, wholegrains, fruit, and vegetables support the SCFA-producing species that help regulate inflammation.

Here's a handy list of 29 high-fiber foods.

2. Eat a wide variety of plants

ZOE research found that people who ate 30 different plant foods a week, including herbs, spices, nuts, and seeds, had higher levels of beneficial bacteria. 

Different plants contain different fibers and polyphenols, which feed different species and encourage a more diverse microbiome.

For advice on how to reach the 30-plant target, watch this episode of the ZOE Science & Nutrition podcast with expert chef Hugh Fearnley-Whittingstall and ZOE's Scientific Co-Founder Prof. Tim Spector.

3. Include fermented foods

Fermented foods like yogurt, kefir, kimchi, and sauerkraut introduce live microbes to the gut and have been shown in studies to increase microbial diversity and reduce markers of inflammation.

If you'd like to try fermenting at home, here's a simple beginner's guide.

4. Limit ultra-processed foods

Ultra-processed foods (UPFs) tend to be low in fiber and high in additives. 

Studies show that regularly eating UPFs is associated with reduced microbiome diversity and higher inflammatory markers.

5. Manage stress and sleep

Chronic stress and poor sleep can both affect the microbiome. While diet is often the easiest to change, maintaining regular sleep patterns and finding effective ways to manage stress can also help.

Summary

We're only just beginning to understand the relationship between dysbiosis and inflammation. 

However, the evidence suggests that an imbalanced gut microbiome can fuel chronic, low-grade inflammation in several overlapping ways, including: 

• producing fewer anti-inflammatory SCFAs

• letting harmful microbes flourish

• weakening the gut barrier

• tipping the immune system toward over-activation

It also works in reverse, as inflammation can worsen dysbiosis, creating a cycle that can be hard to break. 

That's why the most effective approach tackles both ends: supporting your microbiome with a fiber-rich, diverse, plant-forward diet, while reducing the lifestyle factors that drive body-wide inflammation.

FAQs

Here are the answers to some commonly asked questions:

What are the signs of dysbiosis?

There's no single diagnostic test for dysbiosis, and symptoms vary widely. More common signs include bloating, irregular bowel movements, food sensitivities, and fatigue. Some people, however, have no symptoms at all. If you're concerned, speak with your doctor or a registered dietitian.

Can you reverse dysbiosis?

The microbiome is highly adaptable, and research shows it can shift meaningfully in response to dietary change. 

Increasing fiber intake, eating a wider variety of plants, and including fermented foods have all been shown to improve your microbiome composition. 

Also, consider non-diet factors such as exercise, sleep, and stress, which can all affect your microbiome.

How is dysbiosis diagnosed?

There's no universally agreed diagnostic standard. Gut microbiome tests can assess the composition of your gut microbiome through a stool sample and identify the relative abundance of helpful and potentially harmful species. 

Your doctor may also be able to request a stool test. However, the test results are most useful when viewed holistically, alongside diet and lifestyle information.

Is all inflammation caused by dysbiosis?

No. Inflammation has many causes, including infections, autoimmune conditions, obesity, smoking, and physical injury. Dysbiosis is one potential contributor among many, and its relative importance will vary from person to person.