IBS: What’s Dysbiosis Got to Do with It?
Irritable bowel syndrome (IBS) symptoms are very real and uncomfortable. Yet no medical test for IBS exists and it is usually diagnosed after other conditions have been ruled out. With no physical abnormality present, it’s almost as if the symptoms come from some invisible force with the power to disrupt your gut function and your daily life.
Scientifically, it’s true that something invisible may drive symptoms. At least, invisible without a powerful microscope.
This mysterious factor is the community of microorganisms in the gut – known as the gut microbiota. Bacteria make up the majority of this living ecosystem, but fungi, archaea (i.e. ancient microorganisms), viruses, and other life forms also live in the depths of your digestive tract. Although scientists have known about this community of tiny residents for centuries, only in the past two decades have they been able to take a full survey of these microorganisms in the gut—not by observing and counting them under a microscope, but rather through modern-day gene-sequencing technologies.
It turns out these microorganisms have a role to play in IBS symptoms. But how exactly does this work?
Connecting the (invisible) dots
One puzzling observation scientists made in the early 2000s was that people who had experienced a serious gastrointestinal infection had a much greater chance (double or more) of meeting the criteria for IBS after the infection cleared. The infection appeared to have changed the body’s physiology somehow, making the gut symptoms persist. The scientists also found that the individuals who developed IBS tended to have a different-looking gut microbial community from those who did not develop IBS. They hypothesized that infection triggered a disruption to the gut microbes, short-circuiting their normal communication with the immune system and locking the gut in a state of inflammatory high-alert.
Fast forward many studies and several decades later: the scientific work has cumulatively shown that those with IBS have an altered gut microbial community relative to healthy people. This applies not just to people who have experienced a serious gut infection, but to others with IBS as well. And it has implications for how the gut responds to various food particles with various uncomfortable symptoms.
What is Dysbiosis?
Whether triggered by infection or some other factor, a disrupted gut microbiota is a key factor in IBS. Dysbiosis is shorthand for a gut microbiota that looks different compared to that of healthy individuals—and this difference can pertain to the names of the microbes present, or the functions they are able to provide. Nearly always, the dysbiotic gut community is less diverse.
What complicates the picture is that there is no single configuration of dysbiosis. Everyone with IBS may have a slightly different version of a disrupted gut microbiota. But what all types of dysbiosis have in common is that the gut microbiota is not able to keep the immune system in check, increasing the likelihood that an individual will experience gastrointestinal symptoms.
Dysbiosis isn’t the only factor in IBS: genes, patterns of gut motility and sensation, brain-gut communication, and response to stress all contribute to the emergence of symptoms. But possibly dysbiosis is what locks the immune system into a dysfunctional pattern that keeps the symptoms from going away.
Dealing with Dysbiosis
Can dysbiosis in IBS be fixed? While lasting changes to the gut microbiota are very difficult to achieve, studies show that interventions targeting the gut microbial community in different ways can successfully reduce symptoms. These interventions are not as simple as reducing ‘bad’ microbes and increasing ‘good’ microbes, but instead they put pressure on the microbial ecosystem in different ways to restore the functions it’s supposed to provide.
The most dramatic way of trying to change the gut microbiota is through fecal microbiota transplantation (FMT) – that is, transferring the stool microbial community from a healthy donor to the colon of someone with IBS. And although this has been tried in several studies for IBS, the approach is a very broad one that is not guaranteed to resolve symptoms. (Importantly, it is a risky procedure that should never be attempted without the oversight of a medical professional.) The biggest take-away from these FMT studies is the potential for finding more targeted gut microbiota interventions that work reliably for people with IBS.
Specific types of antibiotics and probiotics are also shown to reduce symptoms in some people with IBS. For the duration of the treatment, these interventions alter the microbial ecosystem and may offer relief from symptoms. An antibiotic such as rifaximin, taken orally, cannot escape the digestive tract so it affects the bacteria residing there without being absorbed into the rest of the body.
Understandings of IBS continue to evolve as scientists investigate the force of ‘invisible’ gut microbes that contribute to IBS. As researchers drive towards more precise interventions, one day IBS sufferers may be able to choose from an array of options for altering their inner ecosystems and bringing the microbes back into harmony with the immune system, reducing or eliminating symptoms at last.
Looking for more information on treatment options for IBS? Check out more resources:
CDHF’s myIBS App
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