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#607: Gut Health & Microbiome Testing: What Evidence Do We Actually Have? – Emily Leeming, PhD
00:50:41
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- [00:00]
A
Hello and welcome to Sigma Nutrition Radio. This is episode 607 of the podcast. My name is Danny Lennon. You're very welcome to the show. Today we're going to be talking about a range of topics that relate to overall gut health, specifically to the microbiome, and then of course, how nutrition interacts with this and affects health ultimately, and mainly looking at what evidence we have for a variety of claims that are often made or things that are presumed to be true at this point, and what evidence is behind them, what areas we have, good quality evidence or not, where exactly the field is at this point, and then ultimately, what can we conclude with some degree of confidence right now and what is still up in the air to go through this? I'm going to be talking with Dr. Emily Leeming, who is a researcher at King's College London, is a dietitian and has published work in this particular area. Dr. Leeming has a PhD in diet and the gut microbiome from King's College London, and previous to that she completed her master's in nutrition and dietetics at Monash University, and she has both published work in this area, like I mentioned, as well as being one of the people who has tried to disseminate that information, which can be quite tricky given as this is one of the areas where oftentimes hype goes way beyond what evidence we have. And so trying to do that in an accurate way, but that is also understandable and useful for the general public, can be quite the challenge. So we'll be taking a look at some of these ideas through this conversation. If you are a premium subscriber to the podcast, remember you can get a set of detailed study notes that accompanies this episode, as well as a full edited transcript. You'll also be listening to our Key Idea segment that follows this particular interview. If you're listening over on the free public feed of the podcast and want to get more out of your podcast listening and use it to really learn and retain much more of the information that you hear on these podcasts, then check out what we offer with our premium subscription. It's the way you can directly support the podcast and at the same time get our study notes to each of these episodes, as well as get a premium episode each month that is only available to our premium subscribers. So all of that will be linked up in the description box where you're listening right now. Or of course you can go over to SigManutrition.com and find everything there. Your support is of course, very, very much Appreciated. With that, let's get into this conversation between myself and Dr. Emily Leland. Emily Leeming, thank you so much for taking the time to come and join me on the podcast today.
- [02:52]
B
Great to be here. Thanks so much for having me.
- [02:54]
A
I am very much looking forward to this. We have a lot of ground to cover, as I think we'd been mentioning. But before we get into any of that, can you maybe give people listening an introduction into your work that you do, your academic background, anything else that might relate to what we're going to get into today?
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B
Yeah, so I'm a researcher at King's College London. My background is in the gut microbiome and nutrition, so particularly looking at whole foods and its impact on the gut microbiome and health. I actually do this part time because I have a whole other aspect to the work I do. I'm an author, writer, speaker, a columnist at Daily Mail. So for me, I guess everything that ties it together is an absolute love and passion of science and this background in nutrition microbiome. I'm also a dietitian. And then how can we like translate that into practical, actionable advice? And that's my other half to the work that I do.
- [03:46]
A
I guess that's the tricky thing, and particularly with the topics we're going to discuss today around gut health, the microbiome, when much of that information is typically translated to the public, there can often be an oversimplifying to the point where people come away with messages that aren't really backed up by evidence. And then you're in the position where you are rooted within the evidence as well. Dietitian doing this research, and so are very aware of maybe that that disconnect. And so I think it'll be useful for us to look at some of that. Maybe a good starting point here is around some of those terms that are generally heard that people are referring to, because whether people are trying to improve their gut health generally, or maybe later we'll look specifically at change in the microbiome. These are things now that everyone has heard of, but yet maybe don't align with what we might refer to or if there even is a consensus within academia. So when people use that term, gut health, what are we actually referring to? And for you, at least, how would you even start by coming to some degree of a definition on what that might mean?
- [04:53]
B
I think in the public space at the moment, when we're talking about gut health, a lot of it seems to refer to the gut microbiome, but I think there's really A pushback now to recognizing that we really need to talk about the entirety of the gastrointestinal tract. So starting from the mouth, the tube, going all the way down the system, the organs are involved, going down to the bum, and also including that gut microbiome as a piece within that, we have had different definitions. So there was a definition for kind of what is gut health in 2011, but a lot of that had probably a lesser emphasis on the gut microbiome and more of an emphasis on subjective feelings. We've actually had this new consensus that came out earlier this year that was from a group of experts brought together by the International Scientific association of Probiotics and Prebiotics. And that was really helpful because it gives us a little bit of more of an understanding of what are we talking about when we mean gut health, what factors are we thinking about? And effectively, there were three key elements that they proposed as what we should consider as gut health. Firstly, it's, yes, we want to consider about healthy function. So thinking about that biological side, so that's thinking about digestive physiology, things like the immune system, gut hormones, the microbiome. So all these kind of different domains that are all interconnected and we need to think about them collectively. And then it's also thinking about, well, if you have a disease, if it's in clinical remission, then you can still have a state of gut health. And I think that's really important for, you know, I get asked a lot of questions of people who have a gut health disease condition and they're like, well, where does, where do I fit within that? So I think it's really important that they've included that within this definition. And then last but not least, really kind of thinking about that person's experience, so recognizing that, you know, the gut health symptoms that somebody might have that impacts their quality of life, so basically being kind of free of anything that might be having a long term impact on how you're living your life day to day. So all those things encompassing what gut
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A
health means, and so straight away that makes it, well, we have this kind of broad umbrella term that can include a number of these different components. But then if people are talking about or making claims about either a certain product or supplement or food or diet that quote unquote, improves gut health, there's maybe some distinction needed there. Well, what component of gut health are we aiming that it actually improves or there's been demonstrated to improve because it might nominally improve one part of that, but not others. And so how do we think about some of these claims of something improving one's gut health or not, if that makes any sense.
- [07:40]
B
Yeah, and I think it is really difficult because it isn't completely very complex. And as you say, there's lots of different areas, lots of domains that you can look at. You know, ideally we probably shift to this space that we have specific evidence to show a benefit in a specific part or section of gut health. And then the claim would be made perhaps around that, because I think, you know, it's this kind of broad, all encompassing, very kind of sexy sounding marketing claim that is made at the moment, and yet perhaps a lot of it at the time, it's not much substance behind it. And I think the other key thing, and again, this is something that came up in the consensus statement, was that there's no one test to show that you have good gut health. They're very much bringing all those key elements together. And I think that again makes it even more difficult for which it should do, to be able to make a claim that this then is improving gut health. So we do need a lot more parameters around that because it is a bit of a wild west at the moment in terms of the claims being
- [08:39]
A
made with some of those characteristics. It seems easier to define if there is a state of health or not. So we could say, does someone have certain symptoms or not, or whether their digestive function is normal, as we would expect, or is there some dysregulation? Or maybe we could point to some markers around the actual lining of the gut, whatever the case may be. But when it comes to the gut microbiome, it seems maybe this is a bit more difficult to pin down sometimes in terms of what we would consider to be a healthy composition of that gut microbiome. And what is unhealthy? And maybe more specifically, where does one cross from that line? If it is indeed a line, where is your thinking around the concept of what a healthy gut microbiome is? And is that even the right question? And if so, how. How should we think about healthy versus unhealthy gut microbiome?
- [09:37]
B
I think when we talk about what a healthy gut microbiome is, I mean, I usually want to talk about it. You do these kind of above quotes around the world healthy. Because we're still in such a state of evolution in terms of our understanding of the gut microbiome. It's not that long ago that what was quote unquote, a healthy gut microbiome was like a ratio between certain groups of microbes versus another group of microbes and then now it's more that we talk about how diverse a gut microbiome is. So how many different types of microbes are within that gut? I tend to just talk about microbes, just to clarify, because the gut microbiome is made up of lots of different microorganisms, but mostly we're really referring to bacteria. But it can get a bit complicated. So I'll stick to just saying microbe for now. So we it's this kind of diversity of your different bacteria, your different gut microbes that you have tends to be related in kind of population studies where we look at patterns of population to people who are healthy and don't have disease. People who have conditions or disease tend to have a less diverse microbiome, one that we then think is less healthy. But I think that again, is really where one stepping stone in this evolution of our understanding of what a healthy gut microbiome is. Because diversity doesn't really explain everything in terms of a healthy gut microbiome. For example, you can eat more fiber, which we know is really impactful in terms of your gut microbiome, your gut health, blood. But that probably likely from the research we see, is not going to increase the diversity of your gut microbiome, but it's actually still having beneficial effects on the function. So what those microbes are actually doing for your health we also see, for example, in different life stages. So if you are a young baby or kind of growing into a toddler, you're going to have very limited microbiome diversity. And that's a good thing. It's actually seen as being a problem to have too much microbial diversity as a kind of newborn baby. So there's a lot more to that narrative. It's something that's been. It is a simplistic overview. It's our best case way and measure at the moment that we use as researchers. We look at diversity and see if there's a difference. But it's really recognizing that actually there's a lot more to it. And I think actually we're going to be shifting more towards what molecules are the microbes producing and therefore what function are these microbes having for our health through the different actions that they're taking. And that's likely going to give us our kind of next step in understanding what a healthy gut microbiome is.
- [12:14]
A
Actually something that fits in with that. And that I wanted to ask your opinion on, given your expertise, is that recently on the podcast I was talking with Andrew Reynolds, who has done some nice work around dietary fiber. And recently him and his colleagues authored a comment piece in Nature Food around this concept of dietary fiber being essential or not. Or could it get to a point where it would meet the criteria for essentiality? And one of the things they hypothesized in that was around if we could get to a point where we said a deficiency state could be established for fiber, which we don't currently have, and that deficiency state would essentially be some type of marker or some type of state where there is a quote, unquote dysfunctional gut. So this fits into this concept around gut health. Now they make the clear point that they're. They weren't trying to define what that dysfunctional gut would be. That would be more for people in the area of the microbiome and future work. But as a kind of hypothesis and idea, it's quite interesting of where we could go and potentially get to a point of having a clear criteria or a clear definition of what a dysfunctional gut looks like. And maybe secondary to that, something like very low fiber intakes could be the deficiency state of fiber would be this. Is there any thoughts that come to mind for you based on this kind of hypothesis they've put forward owing to that they've left all the hard work for the people in the microbiome field?
- [13:35]
B
Yeah, I mean, definitely. I think that the fact that we probably do need to kind of broaden what the definition of an essential nutrient is. And I think historically we've looked at, for example, vitamin C and if there's a lack of it, then that is directly causing scurvy. And how can we then look at fibre and it's going to act in a different way. It's not necessarily causing scurvy in that similar sense. But I think, you know what would be interesting if you were. And again, this is off the top of my head, could you see a change in the gut microbiome? But I think it would also be that gut environment as well. It would be maybe like a degradation of the mucus layer. There's. This is a kind of, a kind of protective mesh that covers the lining of the gut and protects the gut lining. You could perhaps see that there's more gut permeability, perhaps that could be related to more kind of inflammatory markers that are happening in the blood. We see that kind of maybe perhaps a crossover of things that shouldn't be crossing over the gut barrel lining and causing a low grade inflammatory state. And I think the key things of all those three, the gut microbiome, the mucus layer. And also this kind of gut permeability is that we just do not have, at the moment, rigorous markers or rigorous ways of assessing them. In a sense that we can understand what is clinically relevant or even just capture that information accurately. So we don't really have a very easy tool unless we're taking a biopsy, for example, of the gut barrier and the mucus layers. So it's very invasive. And then for. We just do not have much research in humans yet we do have signals from. From mice models to show that likely is something that's happening with low levels of fibre.
- [15:19]
A
And I do want to return to fiber specifically, and then also the impact of the diet in a bit. But just before getting to that, as we're talking about the microbiome here, one of the things that you are acutely aware of and everyone listening has seen in at least some degree is now the availability of commercial microbiome testing. And depending on that provider or that company, there are various claims of what that will offer people and what that can. What information that can provide them with, and also its utility. So, from the perspective generally, and then we can maybe be specific from the concept of commercial microbiome testing as is currently available, where would you say the current evidence lies in relation to its clinical utility for actually informing us of something?
- [16:03]
B
It's definitely seen as something that is more useful than, I think, actually where we're at at the moment in terms of the science. I do think there is future potential of it being used in conjunction with other measures, but I just don't think we're really there yet. Generally, what I tend to say to people is if they want to spend money on a gut microbiome test, the things they're going to get out of it are really just understanding which types of microbes, which type of bacteria are present and in what amounts. But we do not have the evidence yet to give any kind of concrete advice or action based on that single report. There's a few reasons for that, and I think this was also really nicely summarized last year. So 2025, there was a group of 69 microbiome experts that came together, and I think there was kind of 90% consensus across these 69 experts that there just isn't enough clinical utility for these microbiome tests at this point in time. I think they very much also emphasize that if someone is going to do a microbiome test, that it's directed by a clinician, it's not something that a customer would go directly to a company for, for example, and they were very clear that at this point in time there isn't anything really particularly actionable to take from those. And again, some queries around how do we say what a healthy microbiome is? And then even just a step back, I mean, we've got to remember that the gut microbiome is a kind of teeming hub of activity. It is constantly changing hour by hour, day by day. So you are really only taking one tiny snapshot in time. And then actually, then if you think about that, even where you're taking your sample of your, you know, take a kind of pea sized scoop from your kind of poo, even within that shape of poo, you're going to have different types of microbes in different spots and different regions. And actually there was another recent paper where they effectively sent off the same samples to seven different commercial testing facilities. They wanted to take out some of the kind of biological differences, so they actually blended the poo to make sure everything was uniform, which obviously wouldn't happen in a normal testing setting. Sent it off. And even within having done that, they found huge difference and huge variabilities between all seven of the different commercial providers. Some saying they had problematic bacteria, others saying completely otherwise. So really showing that we are just not there yet in terms of practical utility.
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A
Yeah, it seems like there's not only one problem, there's problems all the step along the way of making sure. Even just with the testing, the replication of that, like you said, the different samples depending on where someone goes and then even beyond that, even if we were to assume everything that was accurate, then we have to know, well, can we actually interpret what this might mean in terms of these different numbers? And then that's even before thinking about what would be the actual implications practically of what changes someone might bake and would it be different to what we might advise regardless. But it is worth noting that an issue I've had told to me from several dietitians that are working in practice is they're now seeing people that, that come into them with a microbiome test report and asking them to help them with it and they're in a position of saying, well, this isn't really informing me, if anything, but of course they have to interact with that person in a way that is understanding. But it is becoming a challenge for people in clinical practice.
- [19:37]
B
Yeah, absolutely. And I think I really appreciate as well, that person is really seeking a solution for their health. They spent a lot of money because microbiome tests are expensive. So I tend to say, I'm like, please, if you have a gut health problem, please use that money to go see a dietitian and get your individual advice will be from that dietitian who's taking in all these other different parameters that are relevant and not just looking at one single measure.
- [20:02]
A
So if we turn our attention to diet, there's a few specific things that I'd like to get to. But first, and probably most importantly, we can take a look at where we have maybe the most clear evidence, or at least from a broad perspective, related to dietary patterns, what we do know about its impact generally on this concept of gut health. And then maybe within that, we might have to be specific. And at the risk of this being a very broad question, Emily, where would you start off of saying the clearest things we know about general dietary patterns and their influence on gut health?
- [20:36]
B
So, on the whole, we know that kind of broad dietary patterns in terms of eating plenty of plants. You don't have to not eat any meat within that, but we know that that is something that is supportive of gut health and your gut microbiome. To contradict that. We then have the kind of Western dietary pattern which is, we all know, being high fat, low fiber, low nutrient density, being something that is linked to worse gut health in terms of individual foods. We're actually still at a very early stage with that at the moment, in terms of having human range, randomised control trials that show an effect of, for example, we have evidence on broccoli, we have evidence on nuts, I think have been done quite a lot in terms of a kind of tightly controlled setting. Most of the research that we have tends to look at patterns in populations. So is this kind of group of people eating mostly a kind of high plant diet, or are they eating lots of fiber? And then can we see these larger patterns in terms of their gut microbiome? So still very much an evolving state. Again, recognizing that it's really only been the last kind of 20, 25 years that we've had gut microbiome science explode and this kind of tsunami of research come out. So there's lots that we still really want to know and understand, but the key things within that, I think, is also understanding what feeds the gut microbiome and what actually even just gets to the microbiome in the first place. So we've got to recognise and remember that our digestion, yes, starts in our mouth and then it goes down to our stomach. We've got this kind of swirling sack of acid and then through to our small Intestine, which is effectively where 90% of the nutrients we eat are absorbed. And then yes, we have some microbes within the small intestine, but most of them live in the large intestine, which is lower down. Which means that a lot of the foods and nutrients that you eat aren't actually necessarily making their way to your gut microbes, unless you have, you know, a small percent will likely still make that hasn't been digested like I think, I think it's like 10% of protein for example, still makes its way to your large intestine. So really the nutrient that is arriving there is fiber is, plays a key part in that. And that's because we don't have the digestive enzymes ourselves or we're not able to kind of access to the kind of bonds to break down in the fiber in the small intestine. So that fiber acts a bit like a kind of rebel nutrient and says no, I'm not getting broken down by you, the human. And passes through to the large intestine, which is where those microbes can then feed on it. And by feeding on it they make those molecules that for your health, particularly short chain fatty acids, the ones that we get particularly interested by that have anti inflammatory action and can support the health of the gut, but also cross into the body and have different health effects that way as well.
- [23:30]
A
So we have, and particularly fiber is a good example because it seems to be connected to a number of these different but related outcomes. Right. So of course we could note that there might be differences in that microbiome composition based on higher or lower amounts of fiber. But then fiber is also having other roles as we mentioned there. The general health of the gut lining itself could be playing a role here, what metabolites get formed, et cetera. And so there's a number of different things that all relate to good health, affect transit time or all the other stuff we've known for a long period of time, as opposed to it just being one particular thing. When it comes to the microbiome, it seems to be challenging here from looking at some of these dietary interventions because it's quite common to see a, an association held up between some type of diet or maybe a dietary change, oftentimes even just an observation of a diet and some type of microbiome composition or outcome. And I think maybe sometimes not enough of those limitations of that are mentioned. And so for you, I'm sure you're seeing this all the time, where we see this diet led to this type of change in the microbiome or is associated with this type of composition and then that ends up escalating to the point where we see on social media. For you, is there any of those limitations you could make people aware of when we are looking at those types of studies? That just might be some things to bear in mind when we're trying to interpret this, of what it might actually mean?
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B
Yeah, absolutely. I think there's really two things that spring to mind. So firstly, I think we need to be really careful about talking about changes in the gut microbiome if they're not related to a health benefit, a health outcome. Because again, if we think back to this microbiome being a kind of variable living ecosystem, things are changing all the time. And I think sometimes, you know, again, if you're doing these analyses where you're looking at so many different types of microbes within that the likelihood of you finding something is actually quite high. We have to, you know, you've got so many different bets on other things that you're looking on that one or two will likely come through the wash. So actually, is that real and is it meaningful for your health as well? So even if there is a change, does it actually matter in terms of anything that's clinical or how you feel in your body? The second thing is that I very much guard against how we talk about even just the names of certain types of microbes. The reason for that is that yes, we have some groups and some types of microbes that are generally recognized as being healthful. But even like us humans, even the best of us have our bad days and we've seen, for example, like Akkermansia for example, can behave badly in a kind of low fiber environment in relation to I think a peanut allergy. So there's different. And just even to broaden that out, we then have other types of microbes that in, that will be rising and in higher amounts in certain disease states, yet be completely the opposite in other health or condition. So it can play, you know, huge different signals we see across what might be healthy somewhere could be unhealthy elsewhere. And I think so that's something I really, I personally am quite cautious when I'm talking about the microbiome. I really try not to talk about certain types being doing X instead I really try and talk about, well, what are they doing? And thinking about almost the gut microbiome as a company with lots of different workers and teams and that you might have a marketing department and a PR department, you might have a product and a Department and hr. And within that you will have. They'll all be different, doing different actions, they've all got different jobs, but you might have different people within that. So, you know, you and I could be on the same team, but we're very different people. We've got the same kind of output, the same job that we're doing. So it doesn't necessarily matter who we are, but the actions that those microbes are taking for our health, that could be a completely different microbe for one person, doesn't matter that another person doesn't have it, as long as that function is still being fulfilled.
- [27:41]
A
When we go from looking at some of the broad associations we have with the types of dietary patterns where we see beneficial outcomes, down to trying to work out what component of that pattern is responsible for how much of that effect, of course, with good reason, a lot of the focus can be placed on fiber because of its presence in those dietary patterns. But then there's also components of those foods that may have effects that are not mediated through fiber. And one that has been hypothesized and been looked at is the role of polyphenols, for example, or other bioactive compounds. Again, a very difficult and intricate area to look at. Where are we with the current evidence of what we might know or not in relation to the potential role for polyphenols here?
- [28:26]
B
So polyphenols are currently considered what they call a candidate prebiotic. So a prebiotic being a compound or a substrate that feeds a kind of set group of microbes to then have an effect on your health. So there are certain types of fibres that are considered prebiotic fibres, and then there are kind of these novel candidate probiotics, of which Polyphenols and also Omega 3s as well are considered. So considering that they're thinking that, the thinking is that the polyphenols are then feeding the gut microbes to then also help to make these molecules for your health. But again, we're still actually in quite a kind of early stage with that. And I think so much of this is like recognizing how complex and analyzing diet really is, and how do we collect rigorous dietary data when everybody eats in a very different way? And how can we disentangle one thing from another thing? And yes, we have certain ways and approaches in terms of our statistical analysis, to adjust for certain other components that we think might also have an influence. So we can try and isolate perhaps that more kind of direct relationship, but it's never perfect. And I think we've really got to recognize that foods are made up of, you know, 26,000 biochemicals. I mean, there is so much to know and understand still in terms of those specifics. But we do know broadly, generally, that it's a positive thing for your health that eating more polyphenols. We don't yet have a set recommendation in the UK in terms of what our polyphenol intake should be. I think that's going to be a really interesting next step in the research in this area. And again, I think as tea and coffee drinkers, that's something that in the UK we get most of our polyphenols from tea and coffee, but they're found in a wide variety of fruits and vegetables. They give a lot of the colorful pigments to the fruits and vegetables that we eat, as well as dark chocolate and beans as well. Black beans, particularly high in polyphenols.
- [30:26]
A
One of the things that people typically come across when they're looking for information on gut health or maybe even stumble across it online. One of the central recommendations from a practical perspective is often around fermented foods. And it's been maybe a few years at least, since I've really looked at this area, so it could have been changed quite significantly. But I remember a few years ago trying to look at this, particularly when there was a boom of these products coming on the market, and I was actually quite surprised at how little direct evidence there was at that time, compared to the types of messaging, is quite common to see currently. Where are you with something like fermented foods? What evidence do we have? And are you of the position that for people who are interested in generally being healthy and a part of that relating to gut health, that fermented foods offer something beyond not having them included?
- [31:18]
B
So the best study, the strongest study that we have at the moment is one that was done by Stanford University a few years ago. And effectively they had a fermented food group and they had a kind of fiber group and they compared the two. The people who are on the fermented food arm were eating, I think, about six to seven servings of fermented foods a day. So that is quite a lot of fermented foods. And I think for most people it's not very practical. But again, we've got to think in terms of research settings. Quite often the recommendation is quite high because they want to know that they're going to see a very specific signal within a short period of time. So I think it doesn't necessarily mean that that isn't relevant at Smaller levels. But of course, we don't necessarily really know at this point. What they found was that the people who were having the fermented foods at the end of the study, they did have higher levels of microbial diversity and they also, interestingly, had lower levels of inflammation. So that's something that I think is a really interesting takeaway from those fermented foods. If we then zoom out more to, okay, let's look at different types of fermented food and what is the evidence behind them. Most of the research has actually been done on kefir. So kefir being a fermented milk that you can easily make at home. And actually, you know, if you want that kind of microbial richness within that fermented milk, it's going to be likely more diverse in the types of microbes that it has and higher abundance than if you buy one in a supermarket purely because it needs to be shelf stable quite often. And so therefore, there's kind of limitations on how willing companies are to have a live product that could potentially explode and lose the money. So the most of the evidence is around kefir. But again, have we got randomized control trials in humans that are just looking particularly at kefir? I think not. From the top of my head, I can think that we've got kind of small studies that show a benefit, again, if then we look at different types of fermented foods. Kombucha, fermented tea gets talked about a lot, but actually really minimal evidence out there at the moment that we have a handful, literally two or three studies, and not really showing anything particularly significant in terms of either a health benefit or just nothing in terms of that's happening at all. So I think there's a huge discrepancy there between what we can see in the research. And I think with. And we. And we know this in terms of nutrition, right. That we're very good at trying to just pinpoint a food that we think is going to make a big difference. But actually it's really about that overall pattern of the food that we are eating and where does that fit. And is that, yes, wonderful to bring in some fermented foods if you enjoy them and if you like them. But really it's that overall dietary pattern. Yes. Thinking about your gut, microbiome and fiber and drinking enough water, because we know that fiber acts like a sponge and therefore fluid is really important. But I think we've got to even step further back from that and think about. We need to think about whole Body health, because everything is interconnected. Your gut microbes live within your gut, which is part of your body. And therefore we've got to think about all those different aspects of a balance plate in terms of supporting your gut microbiome and not just pinpointing one or two things, as I think I'm likely guilty of as well.
- [34:40]
A
Right at the start, we mentioned about how you are not only involved within the research, but a lot of your work relates to the communication of this science to the public. And oftentimes when people are hearing information in this area, as I'm sure is particularly irksome to you, there's a variety of different claims that people make very loosely at the best of times and. And sometimes just outright come from nowhere. Are there any commonly heard claims that you think are particularly prevalent that bother you, or at least that you see quite a lot that you think we need to add a bit of nuance to? Are there a few that particularly come to mind?
- [35:17]
B
Yeah, there's definitely a few. I think I totally appreciate that it's a very exciting area of science and I think I'm so. I think it's wonderful that people are enthusiastic and passionate and want to know more and want to communicate it. And it is a really hard space to communicate because most people don't have access to the training to really understand. Even if you're a clinician, you're not getting taught about the gut microbiome, though perhaps it may start, hopefully start to moving forwards. There are a few things. I think the key one that comes to mind is this message that I see Everywhere, which is 30 plants a week for a more diverse microbiome. I've had a little bit of a bugbear with this for a long time now. I think my PhD, I was really interested in plant diversity and kind of frustrated at how we had so many barriers to trying to kind of understand even how we collecting this in terms of the dietary data that we're getting and how can we model that with a microbiome? So this is from the American GUT Project, which was effectively a citizen science project of a really fantastic landmark study. 10,000 citizen scientists kind of sending in poo samples and they filled out a number of questionnaires. And the aim of the paper was really, the main aim was not about plant diversity. That was a kind of exploratory finding that was within a subset of people that was further down in the paper. And my slight kind of issue with it is that it's become the kind of gut health slogan that it's this hard, hard evidence that we have that it must be 30. 30 is the magic number and it's been called the equivalent of the new five a day, which I find quite frustrating because five a day is related to many different studies and lots of health effects shown that it's related to lower risk of disease and the huge health benefits that have been very specific to that number. Yet we're talking about what was effectively one guesstimated survey question on collecting dietary data. They asked one question which was how many plants do you think you ate in the last week? Which I think most people would struggle to remember. And then you got a kind of multiple choice of five different options. And then they. The number 30 wasn't anything special, it was just that was the highest intake versus got rid of people in the middle and compared it to the people who are the lowest intake. So people who are eating 10 plants or less. And yes, they saw that the people who ate 30 plants or more had a more diverse microbiome but there was no adjustment for what could. Could it be fiber, could it be eating that they're eating a more plant rich diet overall. So it's not to say like we do know that having a diverse plant rich diet is beneficial, but it's, I think it's so important, even if it's a positive message to still have that nuance and still communicate that number 30 isn't certain that yes, we needed a more diverse diet. We know that that's something that is supportive of your health and your gut microbiome. But that kind of overemphasis of that number 30 has just, I've just seen it, I just see it everywhere and I think we've got to be, I think we got to give people a bit more credit that they can appreciate the nuance and they are making changes for their health and they deserve to know whether the strength of the evidence behind how much effort they're putting in in terms of the things that they're doing right.
- [38:33]
A
Especially when like you mentioned, these are not trivial things to add in. Right. Of aiming for 30 different plants for most people is going to be quite a challenge at first. It's not a trivial thing to change and if we're doing that without really good strong evidence that it's necessary or different to other amounts, then we need to be cautious. One of the other areas that I think is a good demonstration of where we see these major jumps which happens in all areas of nutrition, not only within this area but where we have Some interesting mechanistic work or early work in animal models. And then suddenly we get these various different claims or relates to some of the exciting discoveries in the area of the microbiome, this, the gut brain axis, which I think everyone has heard that. That term a million times now based on some really interesting, fascinating work. And I think it was probably nearly 11 years ago I talked to John Kryon about this, their work in Cork on this. But again, that was this early mechanistic work that they had been doing. And now it's at a point where maybe because people have heard about that, the translation becomes so simplified to the point of taking a probiotic supplement for someone can prevent or even cure something like anxiety or depression. And there's a big disconnect from where we are in the evidence versus some of these. Are there some of those areas where what people think to be true has outpaced where we actually are with the evidence?
- [39:53]
B
I mean, John Cryan's been amazing in really leading the research in this space. I think there's one slogan that I see time and time again, and that's 90% of your serotonin, as in, you know, and as if your happy hormone is made in your gut. And there's some yes and a lot of no wrapped up in that. So what we see is that we have really, your body is making serotonin in your gut, which is actually used for gut motility to help kind of food move through your gut. But that's not able to pass through into your brain. Your brain is making its own serotonin that is acting on things like your mood and different areas of your brain function. Your brain is wrapped in something called a blood brain barrier. And this is a very kind of protective membrane that is very particular about what is allowed to pass through and what's not. The serotonin that's in your gut is too large to fit through effectively some of the gates that are within your blood brain barrier to reach your brain. What we do think is that your gut microbes are influencing the serotonin that your gut uses. But actually, we also think that perhaps your gut microbes are influencing the building blocks that are needed for the serotonin in your brain. So, for example, amino acid tryptophan is used as a building block by your brain to make serotonin. And it seems that the microbes are potentially influencing which pathways, which direction and what use that tryptophan gets used for in your body. Cause as with everything, everything has more than one use in your body and they're helping to support making, getting that tryptophan, which is a smaller molecule and can fit through your blood brain barrier to your brain. But again, is that also, you know, we're at this early stage, there's also thinking that even this serotonin produced in your gut there could be a kind of indirect effect on your mood somehow through different connections, but a lot more to really uncover and understand that.
- [41:57]
A
So if we try and pull some of this into practically what people can take from this and maybe the there's people listening here that are not necessarily working as professionals in the space and just are health conscious and want to improve their own health and are interested in some of these topics. How can we summarize what we can maybe conclude with some degree of confidence that might be useful things for us to do, useful recommendations, diet or supplement wise that we can be fairly sure are going to report some degree of health benefit in this space.
- [42:29]
B
So I talk a lot about the three Fs, which is fibre, fluids and ferments. I would say ferments is a, is a softer F for me. But really those are the things that you know that that fiber and also making sure that you have enough fluid within that, because that is otherwise could cause potentially uncomfortable gut symptoms temporarily if you're not drinking enough water or other fluids alongside increasing your fiber. If you are increasing your fiber, please start low and go slow because it takes time for your gut and your gut microbes to adapt to having more of its food source coming in. And one of the side effects that we see from fiber making those molecules for your health is also producing gas. So that can then have unintended consequences if you're having too much too quickly. I think the big thing for me is that we are very good at understanding if you ask anybody on the street what foods are high in protein, that's something that people can just say, you know, off the top of their heads. We aren't able to do the same when we come to fibre. And I really want to change that. So I have a kind of another acronym which is BGBGs. So think of like the BGS, the 70s boy band who sang Staying Alive. It's BG, BGS and that stands for beans, greens and green vegetables, B for berries, G for grains as in whole grains. And then the S is for nuts and seeds. And those are just a broad, rough overview of what foods are kind of high in fiber. So just remembering those and an easy way to think when you're walking through the supermarket Can I make sure I get those into my basket? I think lastly, we are so inundated with claims and products who are trying to desperately get access to our bank cards. And I think I really, really try and say that the best foundation that you can do for your microbiome is really think about the actions that you can make that are focusing on whole foods. It's also recognizing it's not just diet, it's also movement and sleep and stress. But you don't. For most people, supplements and probiotics are not particularly necessary. There's only a few certain use cases in terms of probiotics where they have a, they've shown to have a certain health effect. It's when you're looking for something like antibiotic associated diarrhea and you want help with that, or you have IBS constipation and there can be probiotics that have good evidence to help with that. But for most people, that money is better spent on helping you eat more healthily in an easier way.
- [45:06]
A
Agreed on that point. It's always surprising that there's, when in general, within the population, when we think of high fiber foods, it often comes down to whole grain cereals or whole grain breads is what comes to people's mind. And there's really forgetting about all the different types of high fiber fruits like raspberries we have or legumes seems to be the forgotten one all the time, which are if we get more people consuming more chickpeas and beans and lentils would be doing great. So I think that's really useful to switch gears then to the other side on a research perspective. We've mentioned that there's a lot of gaps here, a lot of really interesting research questions, some that you and your colleagues are even exploring. What's that most pressing research question that you hope that we can get some answers to related to any of this stuff we've discussed?
- [45:51]
B
Yeah, and I think this, I mean this certainly ties into the study that we're running now is that we know broadly, you know, we have a huge amount of evidence to show that fiber is beneficial for heart health, blood sugar control, in terms of type 2 diabetes, in terms of your digestion and of course the gut microbiome. But I think what's really interesting is that yes, we have this recommendation of 30 grams of fiber a day, but actually as soon as we start going above that, the evidence really kind of drops off because we just haven't got enough people who are eating that amount of fiber. We have historical estimates and Again, this is not to say that we know this for certain, but for example, perhaps our ancestors ate upwards of 100 grams of fibre a day. So I think there's absolutely a kind of space that we need to explore to know is there a kind of increasing benefit? We do see this from some of the extrapolations of some of the studies that we do have that we think that even going even further is likely. Potentially that benefit continues, but I think we really need to do some rigorous studies to understand that. So, for example, the study that we're running at the moment, which we should have results for by the end of the year, it's called the Eat Fibre study and we're looking at the control group, is the recommended UK diet sugar guidelines. So all the advice that kind of comes with that, including 30 grams of fibre a day, and then our intervention group is going 10 grams of fibre more. So it actually is 40 grams of fibre even more beneficial. Are we going to see any more kind of signals in terms of heart health, metabolic health and also the gut microbiome, but all in whole food form. So we're layering extra advice onto, on top of the UK dietary guidelines, giving specific recommendations on whole grains, nuts and also beans and lentils, as like the three key food groups that are the highest in fiber.
- [47:45]
A
Very exciting. And goes, I mentioned to you, a much needed gap in the evidence given where we are and as you perfectly outlined, that we really lack being able to say much once we go beyond some of these thresholds that we've got from much of the work up to this point. So really interesting to see where that goes. But with that, before I get to the very final question, Emily, for people who maybe want to keep up with the work that you're doing and your science communication or anywhere else online, where are some of the places you would point their direction, their attention towards?
- [48:15]
B
Yes, I would say please do come find me on Substack. I write a weekly newsletter. I'm not so hot on Instagram, but please do come join me there too if you'd like. So on Substack, My newsletter is called Second Brain and I write about nutrition, the gut microbiome and basically a space I get to nerd out but share it with everybody else. And then I've also got two books if you're interested in reading more. One is called Genius Gut, about the gut brain connection. And my new book is called Fiber power. It's a four week plan to eating 30 grams of fiber a day and it has 60 recipes in it.
- [48:50]
A
Great. All of that will be linked up in the description box where everyone is listening right now, or over on the episode page so you can go and check all of that stuff out. And with that we get to the final question I always end the podcast on, which can be completely distinct from what we've discussed to this point, if you wish. But it's simply if you could advise people to do one thing each day that would have a positive impact on any area of their life, what might that one thing be?
- [49:14]
B
I think choose kindness to yourself. I think I see that we're very almost too obsessive in trying to categorize things as black or white, as good or bad. And I think really the true zone of health and happiness is just making peace in the grey a little bit more, having a bit of more flexibility, thinking about health and eating healthily is something that can happen on most days, but really keeping space for some joy and pleasure within that as well.
- [49:42]
A
Wonderful. Dr. Emily Leeming, thank you so much for all this information you've given us, for giving up your time to come and talk to me, and for the great work you do. It's been a real pleasure talking to you.
- [49:51]
B
Thanks so much for having me. It's been great.
- [50:07]
A
Thanks so much for listening into today's episode. I just wanted to remind you about Sigma Nutrition Premium. It was created with the goal of allowing you to more deeply understand the material you're hearing and then be able to easily and efficiently revise using things that you have learned. For full details on this, then check out the link in the description box, wherever you're currently listening right now. Or just go to SigManutrition.com and you can see all the details there. I hope you do come back for the next episode, regardless, and until then, have a great week. Stay safe and take care of.