Food poisoning and the microbiome

Via the Q&A section of our site we got the following question: "What is the effect of food poisoning on the microbiome?"

This is a great question, and while we still have a ton to learn about the microbiome (see our first of many posts to come on the topic here) there's actually published research looking into this exact topic that may provide some answers for us. Before launching into that study, let's dissect the question and narrow our focus.


What is food poisoning?

Food poisoning is a broad term that refers to any bacteria or virus in food that subsequently wreaks havoc on your gut, leading to any combination of nausea, vomiting, abdominal pain, diarrhea, or fever. Unsurprisingly, there are a ton of different bugs that can cause food poisoning, and the most common pathogens vary with geography. For the purposes of answering this question I'm going to focus on food poisoning causing diarrhea.

In a study looking at how the microbiome was altered after infectious diarrhea, researchers found a consistent series of ultimately reversible changes.  A huge caveat here is that they only looked at two bugs, V. Cholera and toxigenic E coli (ETEC), both of which can be food-borne illnesses, but neither are common in developed countries compared to other bugs.

During the acute bout of diarrhea, the infection damaged the diversity of the microbiome, allowing simple carbs and oxygen to thrive. This increased the relative amount of bacteria that feed on these two components, and was ultimately followed by proliferation of more diverse bacteria such as those that do not require oxygen and can ferment complex carbs. From start to finish, the process took about 30 days but varied depending on the severity of infection and whether or not antibiotics were used.


Are there long-term effects of food poisoning?

That said, there is a subset of patients with irritable bowel syndrome (IBS) that actually develop their symptoms as a result of a virus; this is called post-infectious IBS (PI-IBS). Ironically, there was actually a large outbreak of food poisoning due to a virus at the annual meeting of the Canadian Society of Gastroenterology Nurses and Associates. A subsequent study surveyed the recovery times, and while most patients had recovered by 3 months, 3% of them had continued symptoms consistent with PI-IBS. Larger meta-analyses have shown that the incidence of PI-IBS was closer to 10% in patients who had an episode of gastroenteritis, a more than a six-fold increase in the likelihood of developing IBS.

That's not to say this process is entirely gut microbiome mediated, but it is certainly reasonable to say it likely plays a large role.

Bottom line? There are many types of food poisoning, and the specific study we reviewed focused on forms of traveler's diarrhea. In these cases, the microbiome followed a predictable series of changes to its diversity, and took nearly 30 days to recover, but there is a ton of variability in recovery times and that is ultimately dependent on the type of bacteria or virus that your gut encounters.

-The Gut Doc


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