Let food be thy medicine and medicine be thy food… when possible!

Javier Aguilera Lizarraga · 15-02-2021 10:00 · CEBE answers

It is said that Hippocrates -considered to be the father of medicine, back in 400 B.C. -already associated a good diet with iron health. Nowadays, it is well known that a varied and balanced diet will help us feel better and healthier. However, for some people, "eating everything" is not an option, as there are certain foods that cause them intestinal discomfort or pain. But, didn't Hippocrates say that food is your medicine? So where does that leave us? Yes indeed, there are people, and not a few, who still don't know why they suffer from intestinal problems after eating even healthy food.

This is the case for people with Irritable Bowel Syndrome (IBS), also known as nervous bowel syndrome or irritable colon. And what is this IBS? In the absence of apparent disease, IBS manifests as chronic abdominal pain or discomfort, as well as an alteration in the frequency and consistency of bowel movements (known worldwide as poop), in the form of diarrhea or constipation (or both!). Once the absence of blood in the stool has been verified, a colonoscopy has been performed (which helps rule out other more serious problems such as digestive cancer), and confirmation that there is no celiac disease or food allergies has been found, the doctor can diagnose the person as having IBS if they suffer from the chronic intestinal symptoms we have mentioned above. This condition, nowadays a great unknown, is quite common -it is estimated that it can affect up to 1 in 10, or 1 in 5 people in Western countries- and is a common reason for consultation in primary care and gastrointestinal specialists.

The reason why these patients suffer from chronic intestinal symptoms is unknown. The vast majority of them agree that diet, and in particular certain foods -such as dairy, gluten products or foods containing FODMAPs (an acronym for foods that contain carbohydrates that are difficult to absorb in our intestines)- are the main cause of their symptoms. Therefore, many believe that they suffer from some kind of allergy or intolerance that is not detectable in the tests. Since the diagnosis of IBS is based on symptoms, and not on anything apparent that can be detected, it is not uncommon to think that the patient is somatizing, or even sort of making it up: "It's all in his head, it's probably stress". Also, the problem is that there is no effective treatment for IBS. Although certain drugs can relieve diarrhea or constipation, when it comes to abdominal pain, nothing works well. Some doctors say it may be best to relax and avoid stressful situations. But it doesn't usually work either.

In a study recently published in the journal Nature [1], my research group (at KU Leuven, Belgium) and I have found a possible explanation for the origin of these intestinal symptoms, showing that they have a biological root, and are therefore not in the patient's head. In this study, experiments on mice show us that an intestinal infection, or toxins produced by certain bacteria, can cause an immune response to develop against certain foods - that is, they are detected as being harmful - if the foods are present at the same time as this infection develops. This causes a loss of tolerance to these foods and, even if the infection is resolved, from that moment on their ingestion will cause abdominal pain and diarrhea, as occurs in patients with IBS. In contrast, if these foods are not present at the time of infection, or there is no infection while it is in the large intestine, tolerance is not lost and therefore IBS symptoms do not develop.

I mean, something of an allergy? Yes, but not really. In an allergy, we find proteins known as immunoglobulin E (IgE) antibodies traveling through the blood. It is currently thought that the role of IgEs is to protect us from parasitic infections. However, in the case of allergies, these IgE mistakenly detect food (or pollen, or dust mites… things that the body should tolerate without a problem) as harmful and alert the rest of the immune system to attack them (this attack is what we call an "allergic reaction"). This is why, if we have an allergy skin test (Image 1), we will have small rashes or oedemas in the places where the allergen - or substance that triggers an allergic reaction - in question has been applied (if we are allergic to something, of course).

Image 1: Cutaneous allergy test. Image taken from Topdoctors.

Wait a minute! Didn’t we say that in order to diagnose IBS, allergies were to be ruled out? That's the fun of it! It turns out that this immune response, with an increase in food-specific IgE production, happens ONLY in the gut and these IgE do not pass into the blood, so the immune response will not be widespread in the rest of the body. Hence, they only develop intestinal problems and these complications cannot be detected with conventional tests. To test this, after demonstrating this in mice, we recruited IBS patients and found that, although they did not show signs of allergy to the foods we studied (with negative skin tests, as in Illustration 1, and no specific IgE in their blood), they did develop an immune response when we administered food - such as soy, gluten, wheat or milk - directly into their large intestine. In addition, we found that IgE levels were higher in the large intestine of these patients than in healthy volunteers (i. e. without IBS), very similar to what our mice showed.

In conclusion, the origin of the intestinal problems of these patients would not be in their minds, but in the biology of their own intestine. This study opens new avenues of understanding an old problem that is still unsolved: the pain of people with IBS. It is undoubtedly a partial relief for these people, who are still waiting for an effective treatment that will solve their intestinal problems once and for all and allow them to eat whatever they want.

Image 2: Biological mechanism proposed in our research study.


Reference research publication: 

[1] Aguilera-Lizarraga, J., Florens, M.V., Viola, M.F. et al. Local immune response to food antigens drives meal-induced abdominal pain. Nature (2021). https://doi.org/10.1038/s41586-020-03118-2


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This blog is supported by the Arts and Culture section of the Spanish Embassy in Belgium and by the Brussels section of the “Instituto Cervantes”, under the SciComm initiative #SPreadScience.

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