Why do antibiotics suppress my food intolerances?

Why would food allergies be affected by antibiotics?
03 October 2017


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I suffer from really bad food allergies, but when recently on a course of antibiotics I was able to eat whatever I wanted and felt fine! Is there an explanation for this?


Gareth Corbett, digestion expert, crunched down on Olivia's query.

Gareth - It’s a great question actually. I think the first thing to talk about is what is food allergy and what’s food intolerance, because I find myself explaining this quite often to patients of mine? Probably the most serious type of food allergy is something, for example, a peanut allergy where you eat a piece of food and you have a widespread reaction to it. You develop rashes, difficulty breathing and so on. That’s a true allergy because the allergy part of the immune system’s been activated by eating that type of food.

Then you have sort of in-between intolerance and allergies. You have things like celiac disease which is a condition where a specific part of food leads to an immune reaction but in a particular place. It’s in the wall of the gut, not causing the whole of the immune system to go crazy.

Then you have intolerances to food. That’s where when we go looking for a problem we take biopsies from the bowel or have a look through with one of the cameras. We can’t really see anything wrong but people definitely develop symptoms when they eat certain types of food. That’s a massive group of people and those people end up being defined by the medical profession as having functional bowel disorders, which is a term that we use when we don’t really understand exactly what’s going on, but we can recognise the syndrome of symptoms that are all together.

What’s probably going on is all to do with the gut microbiota. We have millions, and millions, and millions of bacterial cells living inside our GI tract, and they live with us and we require them to survive. They help us digest our food and they help us sometimes produce important proteins and so on, so they are an important part of our lives. But sometimes things aren’t quite right and the pattern and the types of bacteria that you have growing in your intestine can mean that you don’t digest certain types of food in a way that you might expect, so you end up getting symptoms. People call them food allergies, but they’re almost certainly food intolerances.

What happens normally is that the bacteria metabolise the food and they produce gas. Gas stretches the bowel lumen and the tube of the bowel and that stretches and sends a pain signal up to the brain and says “help.” So you take antibiotics and you end up killing off some of those bacteria and probably by chance in Olivia’s case, the ones that were causing her to have a problem and then she can eat what she wanted. But the antibiotics won’t clear all of them so when she stops, the symptoms can come back again.

Chris - Because basically you relapse back to the normal spectrum of bugs that's right for you or which is normal for you?

Gareth - Yeah, perhaps. Although you don’t always do that and, in fact, what’s more common to see is somebody who’s had a course of antibiotics and then they end up with symptoms afterwards.

Chris - Yes. I’ve got several acquaintances who’ve claimed of this very problem.

Gareth - Yeah. And, of course, the ones that are really big in the NHS is this thing called Clostridium difficile which shuts hospital wards. It's something all hospitals have to report on their Clostridium difficile rates and all that sort of thing. But that’s an antibiotic induced problem rather than an antibiotic preventing problem.

There are other things that alter the system, in the GI tract. One of the things is probiotics. There is good evidence that that helps irritable bowel syndrome.

Chris - So these bugs do survive the journey through stomach acid because one criticism is that when you swallow these things it goes through battery acid in your stomach which deactivates a lot of these microbes and, therefore, the numbers that survive are probably quite small?

Gareth - That may be true for some of the stuff you buy on the supermarket shelves. But there are some products that you can buy as foodstuffs, not prescribed medicines, that contain very high volumes of the bacteria in freeze dried form and so they do make it through the gastric transit. But you are absolutely right, large numbers of the bacteria won’t make it through that acidic environment.

Chris - Where do you stand on transpoosion? The whole idea about crapsules that you pop a pill and it’s a healthy spectrum of bugs to put back in your gut? Everyone's’ grimacing. Sarah, you had your hand up just now, is this something you would indulge in?

Sarah - I have seen it done. Is it freeze dry the poo - is that right?

Chris - Are you actively pursuing this Gareth?

Gareth - We did have what we call a fecal transplantation service at Addenbrooke’s. It might make you laugh. But the bottom line is - one of my colleagues will thank me for saying this, it’s stealing his line. That the stool is basically its own organ. It’s an organ of bacteria. The main therapeutic use is for treating C. diff that won’t get better with antibiotic treatments.  The results are phenomenal for people who won’t get better, they just get better the next day after having this. Whether it will end up being a good treatment for things like irritable bowel syndrome and so on, there isn’t any data that’s firm enough to support that. So I wouldn’t support the recreational use of stool tablets, shall I say.

Chris - I wonder if many people indulge recreationally?  It’s going a step too far.

Gareth - In the same way that people take vitamin tablets and things like that as a kind of lifestyle thing to do to try and make themselves feel better.


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