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In this fourth episode, Ruairi speaks with Dr. Benoit Chassaing from the Institut Pasteur about his groundbreaking research on ingredients within ultra-processed foods, particularly emulsifiers, and their detrimental effect on the gut and the gut microbiome. They discuss evidence from mice and clinical trials.

The Impact of Dietary Emulsifiers on Gut Health: Insights from Dr. Benoit Chassaing's Research

Dr. Benoit Chassaing, an expert in microbiome research at the Institut Pasteur, has been making significant strides in understanding how dietary emulsifiers affect gut health. His journey began with a PhD focused on Crohn's disease and inflammation, which led him to develop a strong interest in the microbiome field during his postdoc in the United States. Today, his research focuses on how dietary additives influence the microbiota and drive chronic inflammatory diseases.

Understanding Dietary Emulsifiers

Dietary emulsifiers, commonly found in ultra-processed foods, are detergent-like molecules that help mix water and oil, improving texture and shelf life. Examples include carboxymethylcellulose and polysorbate 80, which are used in a variety of products from ice cream to bread. Despite their widespread use, the impact of these emulsifiers on the gut microbiome has only recently come under scrutiny.

Key Findings from Dr. Chassaing's Research

1. Microbiota Encroachment and Inflammation: Chassaing's research shows that dietary emulsifiers can disrupt the gut microbiota, leading to microbiota encroachment into the mucus layer that lines the intestine. This disruption is associated with chronic inflammation and diseases such as colitis and colorectal cancer in mice.
2. Role of the Microbiota: The detrimental effects of emulsifiers are largely dependent on the presence of gut bacteria. Germ-free mice, which lack a microbiota, do not show the same negative responses to emulsifiers, highlighting the crucial role of the microbiome in mediating these effects.
3. Personalized Responses: Not all individuals respond to emulsifiers in the same way. Dr. Chassaing's studies indicate that the composition of an individual's microbiota can determine their sensitivity to these additives. Some people may have a microbiota that protects them from the harmful effects, while others may be more susceptible.
4. Probiotics and Protection: The research also suggests that certain probiotics, such as Akkermansia muciniphila, could mitigate the negative impacts of emulsifiers on the gut microbiota. This opens the door to potential dietary interventions that could help protect against inflammation and metabolic disorders.

Implications for Public Health and Future Research

Dr. Chassaing emphasizes the need for more research into the impact of food additives on the microbiome. Current safety assessments do not account for these effects, suggesting a need to revise regulatory standards to include microbiome health. His work also highlights the potential for personalized nutrition strategies that consider an individual's microbiota composition when making dietary recommendations.

Conclusion

Dr. Benoit Chassaing's work underscores the complex interactions between diet, microbiota, and health. As we gain a deeper understanding of how dietary emulsifiers and other additives affect our gut bacteria, we can make more informed choices about our food. Ongoing research in this field will continue to shape public health guidelines and dietary practices, aiming for a future where food processing is aligned with microbiome health.

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Full Transcript 

Ruairi Robertson - So thank you very much Benoit Chassaing for agreeing to have a discussion today. I think you're sitting in the Institut Pasteur where I just left a few months ago. Maybe we can just start off with you introducing yourself and talking a little bit about what you do and what your research field is.

Benoit Chassaing - Yeah, okay, thank you for this invitation to participate. So yeah, we just moved to Pasteur Institute a couple of weeks ago, so it's good to break in all of this process by talking about science for one hour. I'm really glad we are able to set up this call. So yeah, I performed my PhD in 2012, working on adherent-invasive E. coli, so involved in some Crohn's disease inflammation and how those bacteria can induce inflammation. And then after this PhD that was performed in Clermont-Ferrand in France, in the middle of France or in the middle of nowhere, it depends on your point of view. But after obtaining this PhD, I moved to Atlanta in Georgia, United States for my postdoc with Andrew Gewirtz. So, and this is actually at this time where I developed really very strong interest for the microbiome field and working on how the microbiota is established and how the microbiota communicate with the immune system and especially the innate immune system. So we did quite some work on the TLR5 and flagellin recognition by TLR5. And then a couple of few years ago, so five years ago, I moved back to France with my own laboratory, with ERC funding. And I spent five years at Institut Cochin, again working on the microbiota. And again, as I just said, we just moved to Institut Pasteur. And so yeah, working on the microbiota, working on the microbiota mostly from the intestine and working on the microbiota from two aspects. So we are basically working on everything that's before or upstream the microbiota, so how the microbiota is regulated, how the environment, so especially diets, food additives are impacting the microbiota. So this is, I would say half of what we are doing. And the second half is regarding how the microbiota, if it's deregulated or if it's not kept under control, all this microbiota can drive chronic inflammatory diseases, metabolic deregulation, obesity, so we are not working on a specific disease, we are more working on inflammatory processes, and very strong interest of some microbiota mucus interaction because we think it's a very important place where the microbiota is able to drive chronic inflammatory diseases.

Ruairi Robertson - Right, yeah, and you mentioned there your work on dietary additives, and I think that's a lot of what we're gonna discuss today because it's kind of what you're known for and I'm sure what you're continuing to research a little bit. So maybe we can start off, you have done a lot of really exciting work on dietary emulsifiers. So before we talk about their effects in the microbiome, maybe you can just give us a little introduction to what they are and before we talk about what they do.

Benoit Chassaing - Yeah, so what they are. So yeah, we can talk about this for a few hours, so I will try to be a little bit more short. So what they are, they are mostly, for most of them, they are detergent-like molecules, so they are able to form micelles and to combine non-water soluble and water soluble compounds. So this is actually why they are very broadly used. So every package food that's going to contain fat content, which is the case for most of ultra processed food and processed food, will contain dietary emulsifiers to improve texture, extend shelf life, and improve homogeneity of the packaged product. For example, if you buy a peanut butter that's containing dietary emulsifiers, then you will have a texture that's going to be very homogeneous and you will not have oil separation, while if you buy peanut butter that does not contain dietary emulsifiers, which you can find, you will have oil separation due to the fact that there is no emulsifier to keep the oil well incorporated into the product. And so very important for this, for the stability of the product, very important also for the texture. And for example, ice cream, I mean ice cream is a very good example of products that contain a lot of dietary emulsifiers. And for most of the ice cream now you are able to remove the ice cream directly from your freezer, directly put a spoon in it and it's very creamy and it's very pleasant to eat. This is mostly due to the fact that there is a lot of dietary emulsifiers, this creamy texture. Also very broadly used in bread, industrial bread. If you are making your own bread, you will see that it can be sometimes quite difficult to keep all of the gas in the bread before the cooking. And this is exactly why here, that the emulsifiers are used is they are able to keep the gas within the within the bread. So you can see that they are used for many, many properties. It's a very complex family of food additives. It's among the most commonly used class of food additives, the dietary emulsifiers. There is more than 70 that are approved to be used in Europe and in the States. So very complex family and also they are very often used in combination because they do not have all of the same properties, so very often they are combined in packaged products. So you can find packaged products with up to six or seven dietary emulsifiers in them at various concentrations.

Ruairi Robertson - Yeah, so it sounds like there are, in all the delicious foods, ice cream and mayonnaise and bread, but probably not in traditional French baguettes. I'd imagine they're safe.

Benoit Chassaing - Yeah. They are safe. So these are obviously approved for use. You know, they're not, you know, we have very strict dietary regulations in Europe anyway, through EFSA approving what can be added to foods. But I guess a lot of these processes for approving them, I mean, how do they work? I mean, they probably, they worked before we knew a lot about the microbiome. These things were approved. How are these things screened, do you know? Is it for kind of cancer risk, I think, carcinogens or how do you prove them as being safe?

Benoit Chassaing - Yeah, so it's a very important question and very important point. And you're right, but all of this, I mean, most of these food additives were introduced way before we appreciated the very central role played by the microbiota in health and diseases. And actually, it's still the case. So they are not tested at all for the impact on the microbiota. They are tested for two things. They are tested for the ability to induce mutation. So they are carcinogenic potential. And they are also tested for their acute toxicity. So, you know, by injecting them to rats and looking at the acute toxic response in the rat. But that's it. They are just tested for this aspect. And for this aspect, they are perfectly fine and they are not inducing mutation and they are not inducing acute toxicity because you do not have the microbiota in the equation. And what we found in our research, which I'm sure we'll talk about in a couple of minutes, is really the microbiota is a very important driver of the detrimental impact of those compounds.

Ruairi Robertson - Yeah. And so what you have found is that these emulsifiers, which you've described nicely, help the mixture of oil and water together, they essentially do the same thing in the gut. Maybe you can talk to us a little bit about the architecture of the gut and the mucus layer, this kind of lipid-like layer, and what emulsifiers do to that.

Benoit Chassaing - Yeah, because it was actually your question is very interesting because it was actually the beginning of the story. So when I joined Andrew Gewirtz's laboratory for my postdoc, I was, as I told you, I was working on TLR5 and the role played by TLR5 in keeping the microbiota under control and especially flagellating bacteria. But I wanted to have kind of a side project. So this, everything started actually as a side project. And yeah, we were very interested in the mucus layer. In the intestine, you have the intestinal tract, and on top of the intestinal tract, there is a very thick mucus layer that's very, very important to keep the sterility or close to be sterile, the surface of the epithelium. And we know that this is very important. And for example, if you look at animal models that lack mucus layers, they will develop very, very strong colitis and very strong chronic inflammation. Similarly, if you look in patients with IBD, patients with inflammatory bowel disease, you will see that it's very similar. You have a very strong alteration in the mucus layer. So this mucus layer that's supposed to be close to sterility on top of the colonic and the gastrointestinal tract, you will see in those patients that they are actually colonized by a lot of bacteria and they are becoming much more permeable to intestinal bacteria, which we think is very important to drive the chronic inflammation in those patients. So this was actually the... To say also that there are some, you know, commensal or healthy microbes that do live within that mucus layer as well.

Ruairi Robertson - Yeah, it's... And how to regulate that.

Benoit Chassaing - Yeah, it's indeed a fascinating niche. So there is some very interesting and fascinating bacteria like Akkermansia muciniphila that's able to digest and to in turn further favor the mucus turnover and mucus synthesis. So it's a really, again, if you look at IBD patients compared to healthy individuals or patients with obesity, metabolic deregulation compared to healthy individuals, you will see that in all of those patients you clearly have, you know, microbiota, what we call microbiota encroachment. So the ability of the bacteria member to penetrate this in our mucus layer. And we think that this is very, and we have a publication ongoing that really suggests that those bacteria associated with mucus are very key to drive chronic inflammation. And this is actually why we started this project on dietary emulsifiers because we were just thinking, okay, they are emulsifiers, will act like soap or like, you know, detergent molecules. So by getting in close contact with the mucus, they are going to, you know, disrupt, erode, and make the mucus much more permeable to bacteria and hence drive chronic intestinal inflammation. This is actually not exactly how they are working, but what we found was that they are indeed able to drive chronic intestinal inflammation if you give them to mice model. as well as in humans.

Ruairi Robertson - Right, so you think that there is a direct effect of these emulsifiers on this mucus layer because it has lipids and has other things in that's destroyed by these chemicals, but also you think there might be a direct effect or an indirect effect on this barrier through the microbiota and how these microbes maybe degrade or are impacted by these chemicals. Maybe you can talk to us about those two different processes.

Benoit Chassaing - So regarding the mechanism, just before mentioning the mechanism, what we observed was, so again, the first publication was close to 10 years ago now in 2015. And in this first publication, what we observed was that if you give dietary emulsifiers to a mice model, this is going to drive microbiota encroachment. So you will have alteration in microbiota at the compositional level, which is kind of making sense, but also, and more importantly, we'll see how the functional level. So not only the bacteria present in the gut are different, but they are not localized at the same place. So if you eat or drink dietary emulsifiers, those bacteria will be able to penetrate this mucus layer. And those bacteria are also going to express much more pro-inflammatory molecules that will be recognized by the innate immune system. So for example, if you treat microbiota or if you treat animals with dietary emulsifiers, you will have a very, very stark increase in the expression within the microbiota of molecules like flagellin or lipopolysaccharides. So a microbiota with an inherent ability to activate in it is much more increased by the emulsifiers.

Ruairi Robertson - So to explain that visually, you're saying that the emulsifiers were able to genetically change the bacteria and you're talking about flagellin to allow it to swim essentially or to make its way through this sticky mucus layer closer to the barrier and that would stimulate inflammation and problems of the gut.

Benoit Chassaing - Exactly. So we think that this is exactly what's happening. And we're still working on exactly the molecular mechanism, but yeah, exactly. There is some bacteria in your gut that will be able to directly detect those compounds in a way that you will favor the growth of some bacteria and you will favor the decrease of some other bacteria. But more importantly, you will transcriptionally shape the bacteria in a way that this bacteria now is going to express molecules of interest like flagellin and this bacteria will then be able to swim and get in close contact with the mucus. And when we looked at what would be the consequences for the also we use various mice model, but in a nutshell, for every single model we used, we observed that consuming dietary emulsifiers is sufficient to drive chronic inflammation in a way that leads to much more severe disease. So when we looked at mice model of colorectal cancer, we observed that there is more tumor in those mice when they are treated with dietary emulsifiers. When we looked at mice model of colitis, using the IL-10 deficient mice model, in those mice that are genetically susceptible to develop colitis, if you give them dietary emulsifiers, there is much more colitis in this mice model. And we have other work on type 2 diabetes, obesity. We have a publication that we just published on type 1 diabetes and it's kind of always the same observation where every time you give those compounds to mice, by inducing chronic inflammation, this is sufficient to nourish and favor the chronicity of those or the severity of those diseases. So colorectal cancer, obesity, diabetes and colitis in this mice model.

Ruairi Robertson - So you think these effects are dependent upon the microbiota. If you give these emulsifiers to mice that don't contain microbes, the germ-free mice, do they still have as negative effects or is it purely down to the kind of indirect effects they're having through the microbes that are there?

Benoit Chassaing - Yeah, very important point. We really think that the microbiota is the key target. So we have multiple evidence for that. If you take germ-free mice, you give them dietary emulsifiers, they are fully protected against everything. So they are not developing inflammation, they are not developing metabolic deregulations, they are fully protected against colitis. And we even looked because of course, as I mentioned just before, the initial hypothesis was dietary emulsifiers will disrupt the mucus directly and for this obviously you don't need to have a microbiota. So when we looked at germ-free mice that were treated with dietary emulsifiers, we looked at mucus thickness, we look at mucus synthesis, and we also look at mucus permeability and after when we did that we observed that the mice that were either treated or untreated were having very similar mucus layer. So we don't think there is a very strong direct effect of dietary emulsifiers on the mucus layer. Of course, we still need to do some work in this area. Maybe there is some subtle alteration for selective de-glycosylation or select much more subtle differences in the mucus layer. But again, we think that there is no very strong direct impact on the mucus layer. But on the other side, on the other hand, if you take microbiota in vitro... And this time, instead of removing the microbiota from a mice, you remove the mice from the microbiota. So we have in vitro microbiota systems that allow us to cultivate complex ecosystems coming from either our mice or human donor, then by using this system, we are able to reproduce the direct effects of the treat those in vitro microbiota with dietary emulsifiers, you are able to reproduce alteration in composition, alteration in function. There is much more flagellin that's going to be expressed by this bacteria and so forth and so on. So we really think that the microbiota is a key target of dietary emulsifiers. And the last evidence for that is, now if you take those microbiota that in vitro were treated and exposed to emulsifiers, you take those microbiota and you transplant them to germ-free mice. So just transplanting the microbiota, you obtain mice that of course, were never directly treated with dietary emulsifiers, but yet they develop colitis or they develop metabolic deregulation depending on the model you are using. So we really think that those compounds are able to directly impact the microbiota in a way that's going to drive colitis or chronic inflammation and leading to metabolic deregulation, for example. So again, the microbiota seems to be very, very important in driving the detrimental impact of these compounds. So this is why I think, yeah, by screening them for just acute toxicity and the ability to induce cancer, of course, we are thinking is that completely safe. But again, as I mentioned before, if you put back the microbiota in the equation, actually they are very likely not that safe for, especially for the gut.

Ruairi Robertson - And we know about other compounds, you know, in our environment, we know that antibiotics have these detrimental effects on the microbiome as well, of course, being beneficial for destroying infections, but they have these kind of downstream effects as well on other microbes. So Can you quantify that or are there similarities that you can draw between antibiotics versus emulsifiers? Is it a bigger effect? Is it a similar effect? How does the mucus change when you compare these two?

Benoit Chassaing - I mean, the effect, yeah, I would say that the effect observed with dietary emulsifiers, there is, I mean, some of the phenomenon are similar, but the strength of the effect are definitely not the same. So for the effect of dietary emulsifiers, the effects are really, really subtle. And you need to treat, for example, in mice model. And this is what we observed also in the human clinical trial that we recently performed on dietary emulsifiers. If you treat the microbiota with these compounds, you will have, for example, a loss in alpha diversity, so a loss of richness, which we know, a rich microbiota is very important to promote health. And every time you are losing alpha and losing diversity of your microbiota, this is always associated with detrimental consequences for the host. And this is exactly what dietary emulsifiers are doing, but to a much less extent compared to antibiotics. So some of the phenomenon are the same, but again, unlike antibiotics, dietary emulsifiers, you will be exposed to them from your birth and all the way to your life. And they are present in every single packaged product you can think of, they will be present even at many, many restaurants now. They will be using dietary emulsifiers because they are just so easy and so convenient for, you know, making the food looking much better by using them. What's quite fascinating also, we definitely know that the microbiota is very important early in life. There is no doubt about that, and especially a very important role played by the imprinting. So the fact that the microbiota early in life can have very long lasting consequences for intestinal and metabolic health. And guess what? There is a lot in formula for babies. There is a lot of, you know, putting a lot of attention to those compounds. And there is still a lot of things that we need to study and to understand with this compound. We can mention what we are currently doing, for example, in human or regarding, you know, how the microbiota can drive personalized response. But yes, there is also a lot that need to be done in human regarding the potential direct consequences of those compounds on long-term health from the babies, but also to do how you do it.

Ruairi Robertson - Yeah, I think we'll get there talking about the human relevance. But it's interesting what you say about formula feeding because we often think about the differences between formula and breast milk and their effects in the microbiome being due to the things that breast milk or that formula milk lacks and it doesn't have the antibodies and it doesn't have these other important things which are present in breast milk rather than some of these things that there are present which could be causing some of these changes.

Benoit Chassaing - Yeah, yeah. And it's also possible it's a combination of both. And again, And I think this is something we can discuss also a little bit later or now if you want. But again, dietary emulsifiers, if you look at modern food and ultra-processed food, dietary emulsifiers is just one part of the equation. And you have colorants, for example, and there is some very interesting data showing that colorant food coloring can also drive microbiota interaction. The same for various nanoparticles, the same for sweeteners, artificial sweeteners that can all impact the microbiota. So that's also something that we are currently investigating. In the past, we were always looking at dietary emulsifiers kind of one by one, but more and more we are interested in the cocktail effect and looking at the exposome or the fruiting of the microbiota and how the complexity of those food additives can have detrimental consequences in shaping the microbiota.

Ruairi Robertson - So yeah, I mean that leads nicely to talking about that nuance because you had showed before that there are some emulsifiers that seem to have stronger effects than others. Maybe you can talk about that or maybe that doesn't matter now because they're all present in cocktails, are they? Or are there particular foods that contain particular...

Benoit Chassaing - I think it's a very important point and something that we should investigate a little bit more. For this what we did was to use an in vitro microbiota system. So we did not use any mice model or any human clinical trial here because again if you want to look at the detrimental effect of those compounds in mice or in humans, you will need to treat the patient for a very long time. While using individual microbiota system, you can have much faster response. And what we did using the system was to perform a screening of more than 20 compounds and looking at their ability to detrimental impact the microbiota. And what we observed was we are able to reproduce what we observed before again and again, regarding two of them that we use in mice and in humans, carboxymethylcellulose and polysorbate 80. When looking at those two, clearly again, we observed that they are able to induce alteration in microbiota composition and they are able to induce increased flagellin, increased LPS load. So a microbiota with much more increased pro-inflammatory potential compared to the control untreated in vitro microbiota. And then when we tested other compounds, what was quite interesting, I think, and quite fascinating is most of those compounds were behaving like CMC, carboxymethylcellulose, or polysorbate 80. So most of these compounds have also detrimental effect on the microbiota. Some compounds have very, very strong ability to disrupt the microbiota. For example, carrageenan are highly used, for example, in dairy or in fat-free or fat-low cream to replace the fat in this product. And carrageenan, if you look at the direct effect of carrageenan on the microbiota, it's very, very detrimental impact on the microbiota. And what was quite interesting and quite promising, I will say, is we were able to identify a couple of dietary emulsifiers that seems to be very well tolerated by the microbiota. And if you look at the direct interactions, there was actually no response of the microbiota to those compounds at either the compositional or the functional level. So this is bringing to the point where can we have a food industry that's not using dietary emulsifiers at all? I don't think it will be ever possible because they are used for many, many reasons by the food industry, but can we based on this research and based on, you know, putting back the microbiome into the equation, can we identify dietary emulsifiers that should be favored by the food industry and some other that should definitely be banned and not used anymore by the food industry? I think this is definitely where we want to go.

Ruairi Robertson - And do we know what was structurally different about these ones or why were these ones tolerated better by the microbiome?

Benoit Chassaing - Yeah, we don't know. So that's quite fascinating. But the one that seems to be well-tolerated by the microbiota, you know, very different structure between each other and there is not a common feature between them. So yeah, no, we have no idea about that. What we're currently doing, I have one postdoc working on this project, which is quite a fascinating project is trying to understand. So again, we know that the direct effect on the mucus are not strong or to us, at least, they are not evident. However, you have a direct effect of those compounds on the microbiota. And we were able to identify some microbiota members, some very specific strain of E. coli, for example, that we know if you take this bacteria plus dietary emulsifiers, you will have the detrimental response I mentioned before with a very stark increase in flagellin and very stark increase in the ability of this bacteria to induce inflammation. So now we are using this as a model and using transposon mutagenesis and using other molecular microbiology models. to try to identify exactly how this bacteria is able to sense dietary emulsifiers. Is there a receptor? Is there a signaling pathway? We have some candidates that we are currently testing in mice model, and it's quite interesting because the genes that we identify, the factor that we identify are always present at the outer membrane or in the periplasm of the bacteria. So we definitely think that there is some sensory mechanism by select bacteria able to drive the response to dietary emulsifiers. And then, yeah, this is definitely something we want to use later to see if we can identify emulsifiers, but we might not be able to activate such response to those signaling pathways. So this is a work in progress.

Ruairi Robertson - Or it seems what you're saying, if we look at it on the flip side as well, that there are certain microbes that might be in the gut of people that either allow them to tolerate an emulsifier or become more prone to the detrimental effects. You might have a microbiome which makes you more susceptible or more protected. And that comes back to these personalized effects of diet.

Benoit Chassaing - And the personalized effect, this is exactly where my lab is putting a lot of effort right now. Because yeah, you're entirely right. So what we did for, so we definitely think that there is bacteria in the gut that can be either beneficial or detrimental when we face dietary emulsifiers. And for example, we had a publication a couple of years ago where we took animals, feed them with dietary emulsifiers. Again, we observed the alteration in microbial composition. We observed alteration in driving chronic intestinal inflammation and metabolic deregulation. And we did exactly the same approach, but this time by treating the mice with dietary emulsifiers plus a probiotic, which is, as we mentioned before, Akkermansia muciniphila. It's quite a fascinating bacteria that allows to favor the mucus turnover. And we were thinking that maybe by putting back this bacteria, this Akkermansia putting this bacteria into the equation, maybe we will favor mucus regeneration and mucus turnover in a way that we are going to protect against detrimental effects of dietary emulsifiers. And this is exactly what we observed with the observation that by giving the Akkermansia to emulsifier-treated mice, this is sufficient to fully prevent against microbiota encroachment, chronic inflammation, and metabolic deregulation. So we can think that maybe in humans it's the same, the same is applying and this is something that we will be testing. You know, if you have a very, very intact and very, you know, strong mucus layer with a lot of Akkermansia in it, maybe eating or drinking dietary emulsifiers will not be such detrimental for your microbiota. On the other hand, if you have genetic disposition, or if you are lacking Akkermansia and similar bacteria, and you are eating, drinking dietary emulsifiers, maybe this is going to drive to very strong microbiota alteration and microbiota encroachment. But this is exactly what we are working on and very perfectly aligned with this hypothesis and supporting this hypothesis in the first ever clinical trial that we performed on dietary emulsifiers. So we were able to perform this study. And this was a pilot study because there was only a limited number of participants. It was only focusing on studying carboxymethylcellulose. So only looking at one emulsifier and limited also on pilot because we are following those patients only for two weeks. But even with all of those limitations, this is exactly what we observed, that some patients, some healthy individuals, they were not patients, they were healthy individuals. If you gave them carboxymethylcellulose for two weeks, nothing is happening, not much. You have a slight decrease in alpha diversity, no inflammation, and the microbiota is taken away from the mucosa. On the other hand, in some of those patients when you gave carboxymethylcellulose, you have much stronger microbiota alteration at the compositional level and much stronger alteration in microbiota localization with a very, very strong microbiota encroachment. So this is definitely telling us that indeed, if you look at the population, very likely you have individuals that will be much more resistant to carboxymethylcellulose and to dietary emulsifiers in general, and some individuals that will be much more sensitive to dietary emulsifiers. And the beauty of this research is what Noemi did later after we observed this observation She took microbiota from resistant individuals, transplanted to germ-free mice. She did the same with the microbiota from sensitive individuals. And what she observed in mice is, when she transplanted the resistant microbiota, and then you give dietary emulsifiers to the mice, they did not develop at all chronic inflammation or metabolic deregulation or colitis. If you take microbiota from a sensitive individual, you give it to the mice. Now those mice are becoming very, very susceptible to colitis induced by dietary emulsifiers. So it seems that there is definitely something inherently different between the various microbiota, but making us not responding the same to dietary emulsifiers. And this is exactly what we are currently investigating, trying to understand the mechanism and going much deeper also in terms of number of participants because we want to go to the next scale to test this hypothesis much better.

Ruairi Robertson - And I'm guessing that protective microbiota had more of this Akkermansia in it than the resistant ones. And it's quite interesting. It's probably gonna be one of the next big probiotics on the market, because there's some other research showing that it might actually be beneficial for metabolic health and reducing blood sugar and reducing weight gain. And it seems to be quite beneficial in a number of different circumstances.

Benoit Chassaing - Yeah, this is a fascinating bacteria. But again, this is, I think, bringing the concept of personalized medicine, because if you think about this bacteria, and again, there is clear accumulating evidence about the beneficial effect of this bacteria, but if you think about it, it's also a bacteria that colonizes the mucus layer, that's able to digest the mucus layer. So can it be beneficial in the healthy population or patients with metabolic deregulation? Very likely. But think about people like patients with IBD or patients with genetic predisposition to have an impaired mucus layer, will it be beneficial to take Akkermansia muciniphila, which again further digests and further maybe perturbs the mucus layer? Maybe not. So I think we are here again with the probiotic and this is also some stuff that is of interest for us is for probiotic and also for purified fiber, probiotics. I think we are reaching the time to expand the microbiota-based personalized nutrition and personalized medicine, where I don't think there will be a super bug, a probiotic that will work for everybody, but we need to consider something much more personalized and much more microbiota-based in our indication.

Ruairi Robertson - And so have you looked at prebiotics or any foods that are also protective if they were eaten at the same time as these emulsifiers?

Benoit Chassaing - No, this is something we had in mind. So yeah, no, we never tested that. We are currently doing some epidemiological work where we will be investigating that. But in mice model, yeah, no, we never looked at, we never looked at, for example, protecting against the detrimental impact of dietary emulsifiers using soluble fiber. This is something we had in mind for a long time. We need to consider that.

Ruairi Robertson - And so I guess the big question about these kind of studies is a lot of that has been done in mice, but you have some fascinating evidence from humans as well. So how do we translate these interesting effects into humans and what kind of crossover evidence do we have? So first of all, what kind of doses are we talking about in those studies that you've done? How can we quantify that in real terms for someone thinking about their diet?

Benoit Chassaing - So that's definitely a very, very important and very, very tricky question to us because estimating the consumption of dietary emulsifiers by human is extremely difficult because for those compounds are used at a very low level. So you know that it will be present in packaged food. You don't necessarily know at which level and depending on the brand. So for example, if you buy bread, for example, or ice cream, you can think that some of them will be loaded with multiple emulsifiers, some of them will be emulsifier free and for the one containing emulsifiers, they are not going to be the same compounds. And even if they are the same compounds, they will not be at the same concentration. So this is a really fascinating and very tricky field of investigation. So for this, we are collaborating a lot with the cohort NutriNet-Santé, which is a cohort in France, an epidemiological cohort looking at, you know, their dietary food recall for those patients. very well deeply phenotyped patients where we can estimate the exposure to dietary emulsifiers and future health. And we just published three collaborative papers with them where when they looked at the potential association with consuming emulsifiers and health, they observed in healthy populations in France, in the healthy population, if you take the population that's eating or drinking the most dietary emulsifiers, they have an increased risk to develop various types of cancer. They have an increased risk to develop type 2 diabetes, and they have an increased risk to develop cardiovascular disease. So of course, this is pure epidemiological work. So you know that there is an association, you know that there is a correlation, but now you need to test the potential causality of this phenomenon. But we definitely think that this is definitely going in the right direction and in the right place. So to test the causality, we did, as I mentioned before, the first clinical trial using carboxymethylcellulose. But what we did here was very good. pilot experiment and what we did here was very well controlled. So we had a patient under an additive free diet and patient under an additive free diet plus only carboxymethylcellulose that was supplemented. And when we did this study, of course, we needed to choose a dose. And every time you need to choose a dose, you are facing the limit of this approach that we just should we use. Can we mimic chronic exposure to various dietary emulsifiers using only one and so forth and so on. So we were limited. various limits here and some of the critics also by your peers. So again, it was very important to show that we can indeed perform this type of study and it was very important for us to generate hypothesis. But of course, you're right, the dose is a very important question. So what we are currently doing is a new clinical trial in collaboration with the King's College at London with the team of Kevin Whelan and James Lindsay. And what we are doing here, we are taking the program in the opposite direction. So what we are doing is taking patients with IBD, with mildly active IBD patients. So we know those patients have a mildly active IBD. And we are only taking patients that we know are eating some level of dietary emulsifiers. So we are excluding patients that are cooking every meal by themselves and are not eating at all dietary emulsifiers. So we are only taking patients that we know are eating, normal exposure to dietary emulsifiers from their normal food. Of course, they're not taking purified emulsifiers, eating foods that contain dietary emulsifiers. And for all of those participants, which close to 80 participants, we will be just following them for the last time. And for the other half, we'll be performing dietary recommendations and they will be followed by a dietitian to avoid and to cut down their exposure to dietary emulsifiers. So basically we'll have two groups, one group of relatively emulsifier high and the group of emulsifier low exposure. And we are looking at the long-term impact on disease evolution, relapse, chronic inflammation, and so forth and so on. And of course, the microbiota. So I think this is going to be a very, very important study because here we will not be facing any critics regarding doses because we are real life. We are really taking patients in their real life, in their real food, and trying to see what would be the impact of dietary emulsifiers in these patients.

Ruairi Robertson - Sounds fascinating. And I guess that feeds into the larger debate on ultra processed foods and how detrimental they are and whether it's really down to the processing and the additives they contain or whether it's due to the fact that most of the time they contain lots of fat and sugar and things like that as well. So even in your study, you're gonna have to compete with those kind of biases as well because presumably the people who are receiving the emulsifier free diet, if they're getting rid of all these chocolates and these mayonnaise and everything then then their sugar intake is gonna go down and their fat intake is gonna go down. And so how do you control for that as well?

Benoit Chassaing - Yeah, so you want to go a little bit into more in depth for this study. Yeah, definitely we can. It's indeed a very complicated study. So what we'll be doing for those patients. So, and first we also want it to be blinded. So even for the patients that will not be, you know, followed or giving to the, going to the emulsifier low group. even for the patient that can basically keep eating the same, we'll be giving them some fake advice, you know, eat a banana on a Tuesday and eat tomatoes on Thursday just for them, I mean, just to blind the clinical trial. And also what we'll be doing for the second arm, we will be definitely looking at ultra-processed food consumption and estimating ultra-processed food exposure. And yeah, all the dietary advice that we are giving to those patients are really targeted to decrease emulsifier exposure, but not to impact exposure to ultra-processed food. And this is going to be confirmed by dietary recall to those patients. So we are really hopeful to be able to modulate emulsifier exposure without modulating UPF consumption. But again, this is something that we'll know in a couple of months. The study is during its final phase, so we'll have the results very soon. But yeah, no, you're right. We are working on dietary emulsifiers. There is other teams working on other additives. Of course, UPF are also well known for containing a lot of fat, a lot of sugar, and in addition to food additives. And yeah, I think there is a lot, much more that need to be done regarding the impact of diet and Western style of diet on the microbiota in health and disease, that's for sure.

Ruairi Robertson - That's, I mean, it sounds fascinating and it'll give us a real insight. And I'm sure it'll be relevant not only to IBD, but it could be translatable to other conditions as well, and IBS and things that get a lot of greater number of people around the world.

Benoit Chassaing - For sure, and metabolic deregulation, obesity, type 2 diabetes, yeah, for sure.

Ruairi Robertson - So what is the future? I mean, you've mentioned kind of trying to figure out what are the safe emulsifiers. You know, we live in a world where we need to process our food. You know, it's probably not practical that everyone's going to have, you know, fresh fruit and vegetables straight from the farm all the time. And what's the future for both making those foods, but also regulation decisions about what is safe in the food that we eat?

Benoit Chassaing - So I think there is multiple direction we can go into and we are in the lab, we are definitely trying to push in those multiple directions. So first, I definitely think that the EFSA or the FDA in the States should put back the microbiota into the equation. And there is a lot of thinking right now. And there is a lot of, you know, they're putting committees together to discuss about these aspects. I'm part of some of these committees trying to see how we can, you know, use all of the knowledge to acknowledge that okay, the microbiota is not just a piece of poop, it's really doing a lot of stuff for the gut and for intestinal and metabolic health. And we should definitely consider this fascinating ecosystem when we are putting, you know, validating the authorizations and use of new additives and things. So we are definitely pushing in this direction. And regarding the impact on health, I think what will be the future will be used really to use the microbiota field of research for personalized medicine and personalized nutrition. I think we are not yet at this stage, so of course you can definitely have your microbiota analyzed if you pay a couple of hundreds of euros or a couple of hundreds of dollars. I don't think we are at the stage where we can use this data yet. Will we be able to use this data for the general population? Maybe but in a very distant future. But I really think that's very close. I mean, in the next decade or so, I really think that we'll be able to use this data for patients with various types of diseases. And for example, you can think that if we're able to identify a signature of sensitivity to dietary emulsifiers, and then you have a new IBD patient that's coming to clinic, you identify that this microbiota is fully resistant to dietary emulsifiers, then while bothering him with dietary advice, that's not going to impact his disease. Maybe he just can keep eating and maybe his disease is more related to genetic predisposition. Or you can do many other things to modulate diseases. On the other hand, if you have a patient that arrives with a new Crohn's disease or ulcerative colitis, you identify that the microbiota is sensitive to dietary emulsifiers, and this is a patient that's eating and drinking a lot of dietary emulsifiers, can you have a beneficial impact on the disease course and disease evolution, chronicity, severity of the disease by recommending this patient to shut down and to decrease dietary emulsifier exposure? I really think it can be so clear, and this is something we are currently testing. And I think this is where the field is going in terms of personalized medicine and personalized nutrition. If you think about some other work or so where they're trying, you know, there is some patients that are highly responsive to anticancer drugs, immune checkpoint inhibitors. There is some patients that are highly sensitive, some patients that are highly resistant to this therapeutic. We know that the microbiota is playing a central role. And now you even have clinical trials where they're trying to convert a non-responder human to a responder human before going to an immune checkpoint inhibitor in facing a cancer therapy. So I think this is really fascinating feed can with the same apply later for nutrition. I really think so. We are facing a lot of work to do and we are definitely working hard to achieve these next steps. But yeah, I would say that this is the two directions where the field should be moving. It's changing the regulation and putting the microbiota into the equation and also using the microbiota knowledge for personalized medicine and personalized nutrition.

Ruairi Robertson - Right. Well, we'll all be hoping that you can discover the probiotic or prebiotic or diet that we can take so we can keep having our chocolates and ice creams and process. Well, I think we'll leave it there. But I'd like to say thank you. Thank you very much for a fascinating discussion, Benoit, and looking forward to what you uncover with your future research.

Benoit Chassaing - Thank you. Thank you very much. Thank you for the invitation.