Understanding How Gut Dysbiosis Contributes to Disease

Editor's Note: This article was originally written by patient expert Aaron Blocker.

Dysbiosis: What is it?

In healthy humans, the Gastrointestinal tract (GI tract) is populated with a vast, diverse population of microbes (tiny organisms) that make up our gut microbiome. When the gut microbiome (natural flora or bacteria, viruses, etc. living in the gut) is in a healthy and balanced state, these bacteria are actually benefiting you by protecting you from disease.

More often than not we have a balanced relationship with the bacteria in our gut, where the good bacteria help keep the bad bacteria under control. When it comes to the gut microbiome and how it relates to disease you will often hear the term dysbiosis or dysbacteriosis. Dysbiosis is essentially an alteration in the bacteria that live in your gut, which leads to negative health effects and promotes disease. In short – dysbiosis are the bad guys. Contributors to these ‘bad’ bacteria are: fungus/yeast, parasites, viruses and pathogenic bacteria.

Under certain circumstances this imbalance of bacteria or dysbiosis occurs and is believed to contribute to certain diseases such as inflammatory bowel disease (IBD). There is still much debate about what defines a true dysbiotic state because everyone has a different population of bacteria that live in their gut. This makes it difficult to determine at what point a person’s gut microbiome is in a state of dysbiosis. Inflammatory Bowel Disease is the most understood disease when it comes to dysbiosis, and there is general agreement in the scientific community on what defines a dysbiotic gut microbiome. The next logical question is “how does it occur?”

How does dysbiosis occur?

For the sake of making this a little easier to understand – let's assume that when we first get our microbiome from our mothers at birth most of the bacteria are beneficial. This is true to an extent, but the type of bacteria can differ due to multiple factors. Something like changing your diet, smoking, and alcohol can all change your gut microbiome composition. Additionally, things like infection or medication can also cause major changes—antibiotics are a huge factor here.

Side note: Not all imbalances or minor changes in the gut microbiome are considered dysbiosis. The levels of bacteria and type of bacteria in your gut often change and cause no problems. Dysbiosis occurs when the bad bacteria are taking over and the good bacteria are being depleted.

Gut dysbiosis and diseases

An important question concerning dysbiosis and disease is “which one comes first? “Does the disease itself cause the dysbiosis, or is dysbiosis causing the disease? One thing we know for sure is that in a disease such as IBD there is a marked dysbiosis when comparing IBD patients gut microbiota composition to those of someone who has no underlying chronic illness. Even current research shows that if you take the bacteria from an IBD patient and put them in an animal model such as mice, those mice will start showing some of the clinical features of IBD. What is really cool is that this is all very new! I have read articles where scientists have said: if you would have asked me 5-10 years ago if the human microbiome or gut microbiome was contributing to disease I would have told you no.

The reality is there is still so much we do not know when it comes to gut dysbiosis and disease. Every day something new is being published and we realize how much the gut microbes contribute to disease. Gut dysbiosis is also being shown to play a role in other diseases as well such as (Multiple Sclerosis and obesity), but the role it has in IBD is relatively well-characterized. Research is even showing that IBD patients have very different gut microbial composition when compared to IBS patients. This could eventually be an added diagnostic tool when trying to distinguish between IBS or IBD in those cases that are difficult/ more challenging to diagnose.

It is very clear that the gut microbiome is important to overall health. How important? This is an ongoing question. I believe that determining the bacterial composition of someone's gut and working to change it will be a part of many clinical practices in the near future. Will it be the “end all be all” to some diseases? No. But it will probably play a huge role in how we treat certain illnesses. Don’t count those bad guys out just yet – they could end up being the key to a healthier future.


Buttó, L. F., & Haller, D. (2016). Title: Dysbiosis in intestinal inflammation: Cause or consequence Dysbiosis in intestinal inflammation: cause or consequence 1. International Journal of Medical Microbiology. http://doi.org/10.1016/j.ijmm.2016.02.010

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