Best of gut health: Anniversary edition

Gut health is a topic we talk about a lot at ZOE. The gut doesn’t just fight disease, it boosts our mood, processes energy, and does so much more.

Today’s bonus episode journeys through everything we’ve learned about gut health so far. And what a myth-busting journey it is!

In this episode, Jonathan delves into the microbiome, highlighting the most useful tips from conversations with ZOE’s U.S. medical director and resident gut health expert, Will Bulsiewicz, and Tim Spector, one of top 100 most-cited scientists and the author of Food for Life.

If you want to uncover the right foods for your body, head to and get 10% off your personalized nutrition program.

Episode transcripts are available here.

Will’s book, Fiber Fueled, is available to buy here.

Tim’s book is available to buy here.

Links to some things we reference in today’s episode include: 

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[00:00:00] Jonathan Wolf: Our guts help fight disease, process energy, and boost our mood. They're more important than we ever imagined, but why? And what's going on down there to make this the case? Today, we journey into everything we learned about gut health on the podcast so far, and what a myth-busting journey it has been!

Our journey involves blue poo. It will show you how your marriage might affect your gut health, why heartburn medications might not be a good. And provide a comforting reminder that you have the power to make change. Nothing is set in stone when it comes to your gut health. Let's dive in and take a look back at some of our most eye-opening episodes, exploring all things gut health, and we're going to start with your bugs.

That's right. Your gut is packed full of them, and that's a good thing. The trillions of bacteria that live inside our guts make up what's called a microbiome. It's something we've learned about only. For instance, did you know that in just a few weeks you could alter your microbiome through what you eat?

In this episode, I'm joined by regular contributor and ZOE's U.S. Medical Director Will Bulsiewicz, board-certified Gastroenterologist and New York Times bestselling author of the microbiome book Fiber Fueled. Will, thank you for joining me again today. Why don't we start, as we often do with a quickfire round of questions from our listeners around this topic of the microbiome.

Are bacteria bad for us?

[00:01:27] Will Bulsiewicz: No, it's actually time for us to reevaluate because most bacteria are good. 

[00:01:32] Jonathan Wolf: Does everyone have a gut microbiome? 

[00:01:35] Will Bulsiewicz: Every single person, yes. Every single person throughout human history has had a gut microbiome. 

[00:01:41] Jonathan Wolf: Awesome. So if you're listening, you have one too. Does your gut microbiome affect your health?

[00:01:47] Will Bulsiewicz: Absolutely, yes. In a extremely powerful way, which we're gonna talk about. 

[00:01:51] Jonathan Wolf: Can gut bacteria change your mood? 

[00:01:54] Will Bulsiewicz: Yes. There are studies that indicate that our gut bacteria actually are intertwined with our mood. 

[00:01:59] Jonathan Wolf: Can you change your gut microbiome with food? 

[00:02:02] Will Bulsiewicz: Yes, 100%. In fact, changes will take place very quickly.

[00:02:07] Jonathan Wolf: It's only been in the last 20 years that scientists started to observe and understand the gut microbiome. Now we're at a really exciting point. We're beginning to see how we might even be able to manipulate the microbiome for applications in medicine. One fascinating area of research is the interaction between gut microbiomes and our weight.

What's the evidence for the way that it can impact our metabolism and our weight? Because I think a lot of the initial studies around the microbiome actually really started in this area, didn't they?

[00:02:38] Will Bulsiewicz: Yeah, they did. So some of the completely eye-opening studies from around 2006 where they showed that you could actually transfer a body habitus, meaning like a body.

Through the microbiome in mice. Let me share a fascinating twin study where they took two identical human twins and one was obese and one was skinny. Okay, so they have the same genetic code, yet they are not the same in terms of their body habits. One is obese, one is. and they actually took a microbiome specimen from these humans and transferred it into mice, and then fed these mice, the exact same food.

So one mouse receives the microbiome from an obese human, and the other mouse receives a microbiome from a skinny human. These mice received the same food and they consume the same number of calories, and yet the mouse that receives the obese microbiome becomes obese, and the mouse that receives the skinny microbiome becomes skinny even though they're eating the same number of calories.

It challenges in many ways, the calories in, calories out paradigm that many people have been suggesting is everything that matters in terms of our weight balance. We are more complicated than that, and part of what's necessary when we evaluate our metabolism is to actually look at the gut microbiome. 

[00:04:12] Jonathan Wolf: We know the microbiome is affected by what we eat.

In fact, if you change what you eat, you can see changes in some cases within the space of a few days. Will, you know, if somebody's listening to this, they're really convinced that their gut microbiome matters to them and they're saying, you know, can you give me like three tips around food? Because you talked about some other things.

There's sort of three tips around something that we can do around food that might be able to be positive for my gut health. 

[00:04:38] Will Bulsiewicz: Absolutely. So if I'm afforded three opportunities, three tips, the first thing that I would do is to say that we need to increase the consumption of plant food in our diet. Now, this is not necessarily applicable to every single person.

You might be 90% plant-based, and that is a very healthy diet, and I celebrate you. But in the US, and this is not radically different than the UK, the average person is only 10% plant-based. That means we have a lot of room to increase our plant food consumption because these are the foods that our microbes love to eat.

The second rule from a dietary perspective, and this applies to everyone, no matter how healthy your diet is, is that we need more variety in our diet. The food system actually doesn't want this to happen. 75% of the calories that come from plants come from only three plants, wheat, soy, and corn. So if it's going to happen, if we're gonna eat more variety of plants, it has to come from within.

We have to be the ones to initiate this despite the system. And so I encourage everyone to focus, make this a focus with your food, with every meal, eat a wider variety of plants. And the third thing is that we're in an exciting time because science is validating things that we've believed to be true. Yet, didn't yet have the research studies to back it up until recently.

And just in the last year, new science from Christopher Gardner, who's one of my partners on the ZOE Scientific Advisory Board, he's at Stanford University and in collaboration with Justin and Erica Sonnenberg, also at Stanford University, they looked at an intervention where people consumed more fermented food and in just 10 weeks of increase in their fermented food consumption.

They were able to increase the diversity within their gut microbiome and reduce measures of inflammation. That's powerful. 

[00:06:36] Jonathan Wolf: That's amazing, isn't it? But the thing is, factors other than food also affect the microbiome. These can include how well you're sleeping, what exercise you're getting, the time you spend outdoors, or even whether you choose to have pets at home.

And there's another factor that I, for one, was really not expecting. 

[00:06:56] Will Bulsiewicz: Jonathan, this is new research that actually I find to be very exciting, where they have shown that we share microbes with our spouse and actually we share more microbes with our spouse than we do with our siblings, even though we are in the same family and we share genetics.

In this study, Jonathan, what was fascinating is that they discovered that partners who feel very emotionally connected to one another, share more microbes together than partners who, for example, feel distant and separated. And we are social creatures. 

[00:07:37] Jonathan Wolf: Oh, that's amazing. So there might be some new relationship tests.

I love the idea of this where we can both get our microbiome sequenced and you can figure out like how well the relationship is going with like, uh, an external scientific test, it's gonna completely blow the minds of the marriage relationship business. 

[00:07:57] Will Bulsiewicz: Now that would be interesting and perhaps quite controversial, but that would be an interesting thing for us to do.

[00:08:02] Jonathan Wolf: And there's one more crucial relationship you can't neglect when it comes to your microbiome. 

[00:08:07] Will Bulsiewicz: The other thing too that's important, like very important is the relationship that we have with ourself. We have to love ourselves, and if there are things that are unsettled that are bothering us, there's actually physiologic ways.

This is not woo boo, this is actually science. There are physiologic ways in which during times of stress, our pituitary glands will release a hormone called C R H (Corticotropin Releasing Hormone), and that will set off a cascade of stress response, that if you follow it down to the gut microbiome, you will discover that the gut microbiome becomes disturbed.

We use the word dysbiosis, and this is why in times of stress, many of us will manifest digestive symptoms like diarrhea or abdominal cramping or bloating. The gut is connected to our mood. 

[00:09:02] Jonathan Wolf: So the gut is connected to our mood. I don't know about you, but I find that quite exciting or maybe scary, depending upon what you're eating.

Either way, we're learning so much more about how our mind and our body are linked.

Another area we're learning lots about is intermittent fasting, particularly a type of intermittent fasting called time-restricted eating. This is an eating pattern where you would generally extend the time that you're fasting while you're asleep. So instead of your normal sleep where maybe you would, uh, go to bed at 11, you might eat at 10, start eating again at seven in the morning and maybe only fast for 10 hours.

You'd actually extend that to, for example, 14 hours. And then you'd eat all your meals and stacks during the set time window of 10 hours. But how does fasting effect our gut health and our gut? When we were looking for someone to speak about what's happening in our gut when we fast, we didn't have to look very far.

In fact, one of the leaders in this field is someone I speak to most days and someone you likely know too. 

[00:10:13] Tim Spector: I'm Tim Specter. I've been studying the microbiome for 12 years now, who I do research in this area. Uh, I have a medical background. 

[00:10:21] Jonathan Wolf: And more importantly in Tim's estimations when it comes to fasting.

[00:10:25] Tim Spector: I've also tried it myself, so I've got some practical experience. 

[00:10:29] Jonathan Wolf: If you don't know Tim already, he's one of the world's most cited scientists. When it comes to what's going on inside our gut, when we fast, Tim says a lot of this comes down to two different teams of bacteria that operate inside us. 

[00:10:41] Tim Spector: We've known for a while that when you fast, a different set of bacteria appear in your gut because bacteria replicate every hour or so, and when there's no food for them, suddenly the group that depend on food die away or go into a bit of a sleep and others that live off the debris and the rubbish that's left behind come outta the woodwork and multiply. 

[00:11:04] Jonathan Wolf: Each time you eat. The brain sends signals to the gut. Mobilizing an army of specialist microbes. Some get to work on fiber, some on fats, but others aren't interested in the food we eat. They have a taste for something a little more human.

One such microbe is named Akkermansia Muciniphila, catchy name I know. Well, these little critters love to chow down on our mucus. So when the Food Loving Microbes disappear, Akkermansia comes out in force.

[00:11:31] Tim Spector: And it then feeds off the surface of the gut, which is free of food and free of these other food eating microbes.

So, it eats the sugars that are on the mucus layer of the gut, and it basically trims them down so that you get a nice, smooth surface. This then allows the gut layer to keep regenerating new cells.

[00:11:52] Jonathan Wolf: Having bacteria eating away at our bodies from the inside. It doesn't sound good but Tim says it's not really that different to having a manicure.

[00:12:02] Tim Spector: You know, we cut bits of our body off all the time, like our hair and our nails, and we are constantly shedding our skin, so our bodies are constantly repairing in ways we can't see. This is a natural phenomenon. It's an essential part of our repair processes and keeping our immune system strong, that means that all the time, dead tissues are being removed, and this allows all fresh tissues to work perfectly. 

[00:12:27] Jonathan Wolf: We'll take Tim's word for it. So we need to give the nighttime microbes a chance to play away from the greedy calorie hungry day crew. 

In a nutshell, you have one set of bugs who love to chow down on our food. They're pretty wild and they don't half make a mess. Then at nighttime, another bug crew comes out in order to take out all that rubbish, but they can only work if you give them the time and space to do so.

In other words, there can't be any food around, which means you're fasting. In fact, some people who have shifted to intermittent fasting say they have more energy, better mood, and even experienced weight loss. Though this doesn't work for everybody, and I have to admit that I am miserable when I'm intermittent fasting, I have less energy and worse mood.

So as always, these things can be personalized.

So we know the gut microbiome is hugely important, and that positive changes to diet and lifestyle will help your microbiome thrive. But what if you are having gut issues like constipation or heartburn? They're incredibly common. We're going to look at some of the most common of such pesky digestive issues.

Firstly, the dreaded heartburn, also known as acid reflux. 

So let's start with the basics. I did some research and although it's cold heartburn, it's not actually your heart that's burning, but it's this sort of burning sensation in the chest caused by acid from your stomach. How does this happen, Will?

[00:13:58] Will Bulsiewicz: Heartburn can occur when acid from your stomach travels in the wrong direction back up into the esophagus?

You have to understand, Jonathan, the lining of your esophagus is very different from the lining of your stomach. It simply isn't designed to handle acid. So what happens is the acid causes injury in this area, and it can be either microscopic or in some cases even manifest as a full-blown ulcer. So heartburn is what you feel when the acid is irritating the nerves.

[00:14:22] Jonathan Wolf: Then I guess that's where, you know, for the audience who's familiar with many of these symptoms, they're like, okay, so what do I do? And I think they go to the doctor and they take these medications that are used to treat heartburn. Can you tell me a little bit more about them? 

[00:14:38] Will Bulsiewicz: Sure. So the most common we use medicines are called proton pump inhibitors.

They have drug names like Omeprazole, Lansoprazole, or Pantoprazole. So these medicines, they work by blocking the stomach acid from being secreted, which makes people feel better because what reflexes into their esophagus is now less acidic. 

[00:14:57] Jonathan Wolf: So far so good. But what's concerning is when people depend on these medicines to suppress the symptoms.

And so why is that a problem? Will, I mean, there's lots of medication that people use for decades for their blood pressure or whatever. And why are you concerned, and I'm guessing this is linked to your explanation, that the medication actually reduces people's stomach acid for the long term. 

[00:15:22] Will Bulsiewicz: Jonathan, we, we evolved to have stomach acid for a reason, and so reduction of stomach acid can alter the balance of bacteria, it can increase our risk for infections. There have been a number of infections that have been associated with taking these medicines chronically. One specifically that people may have heard of is called Clostridioides Difficile, or more commonly referred to as C Diff. 

[00:15:44] Jonathan Wolf: And I'm guessing that in addition to this, if we are reducing our stomach acids, then it's, it's somehow going to alter the way that our bodies are going to process the food that we eat.

[00:15:53] Will Bulsiewicz: Yeah. The stomach acid is in fact a part of our digestive process, and so it, it can change how we digest our food and this, this could affect access to our nutrients. So those who regularly consume heartburn medications could potentially become deficient in vitamin b12, calcium, iron, just to name a few.

[00:16:09] Jonathan Wolf: Of course, this isn't to say you should never take heartburn medicine, but Will is saying it's worth looking at the other ways to tackle heartburn. Although you may not like his advice very much. 

[00:16:20] Will Bulsiewicz: Sorry to the listeners at home, just the messenger. The reality is that lifestyle choices and foods that we often find to be fun can actually provoke acid reflux.

So just to name a few spicy or acidic foods like citrus and cooked tomatoes can irritate the esophagus and aggravate the symptoms. You'll wanna be conscious of fat intake from fried foods, meat, full fat dairy. And the reason why is that the fat slows down the stomach emptying, which can worsen reflux and some sweet treats like chocolate or peppermint, they actually relax the lower esophageal sphincter. So these things also could potentially make things worse.

[00:16:54] Jonathan Wolf: Apparently, ideally, you also want to go to sleep with an empty stomach, which means three or even four hours between dinner and bedtime.

The next common issue: gas and bloating. Studies estimate that one in six of us experience these discomforts. Many of us think gas and bloating is the result of having a lunch that's a little indulgent or eating certain foods that cause excess gas, but there's actually a lot more to it. 

[00:17:24] Will Bulsiewicz: What's happening with your body is a bit more complicated.

That's the thing that people need to understand. If we want to get better at managing. The bloating issue, we have to actually understand the nuance. That's what's gonna allow us to get there. 

[00:17:34] Jonathan Wolf: So you're saying there's quite a lot of different things that might be going on that explain why I might be suffering from it?

[00:17:40] Will Bulsiewicz: Exactly. In fact, I would say there's four main causes of bloating that are worth discussing. The first is swallowed air, second constipation. Third is a struggling microbiome, gut microbiome specifically. And then the last is our food choices. In my experience as a gastroenterologist, the number one cause of gas and bloating that I've seen is actually constipation.

And in people who are constipated, the most common symptom that they experience is gas and bloating. 

[00:18:09] Jonathan Wolf: So these two are very sort of tied together, Will? 

[00:18:12] Will Bulsiewicz: Yeah, they're very much intertwined. And you know, we actually have research, Jonathan, showing that people who are constipated, they produce more bowel gas.

[00:18:22] Jonathan Wolf: So in these cases, if you can remedy the constipation, you can hopefully offset some of the unpleasant side effects of bloating. 

[00:18:28] Will Bulsiewicz: Yeah, that's actually what I typically will strive to do as a gastroenterologist is from my perspective, I want to get them into a rhythm and get their bowels more regular. And if you can accomplish that, what I typically have seen is that the gas and bloating goes away.

[00:18:41] Jonathan Wolf: And when it comes to nutrition, Will has another tip that's a little hard to swallow. 

And from your experience Will, what would you think are the two biggest areas of concern? If somebody is experiencing chronic gas and bloating and listening to this?

[00:18:54] Will Bulsiewicz: I have advice that I routinely would give to people who come in with gas and bloating, like literally on the first visit.

And that would be to eliminate non fermented dairy and artificial sweeteners. 

[00:19:08] Jonathan Wolf: Okay. Now let's get into one gut issue that people often think they understand, but may not. Constipation. You may be very surprised to learn you can have a bowel movement every day and still be constipated. 

[00:19:22] Will Bulsiewicz: The formal definition, just to be clear for constipation, is having fewer than three bowel movements per week.

Now let me just say like, as a gastroenterologist, I actually find this definition to be too narrow and simple. It doesn't cover all the forms of constipation that I've seen in the clinic. Constipation is incredibly common, and there's been some recent data that suggests that a quarter of people worldwide have at one point reported constipation symptoms.

The survey conducted by Kings College, that actually indicated that a third of the patients, they weren't even able to recognize the signs of their own constipation when they were describing their symptoms. They didn't even make the connection between their symptoms and constipation. 

[00:20:01] Jonathan Wolf: You know, I find that really interesting because when I think of constipation, I think it's really simple.

I have a, like a very simple image in my mind of spending a long time on the toilet, probably unable to pass, you know, a stool, a poop at all. So that's what it would mean to me. Maybe combined with the feeling of not being able to go at all, you know, other times during the day. So maybe like, normally I am going every day, but now you know, I'm on the third day of my holiday and you know, nothing's happened or like I'm going and I can't sort of fully empty myself.

[00:20:36] Will Bulsiewicz: And I would say honestly, that you just summarized many of the forms of constipation that can exist that don't necessarily meet into this definition of less than three bowel movements per week. Those are absolutely signs to look for Jonathan. And it could also even include, believe it or not, the idea of not feeling the desire to go, or not even feeling the instinct like, hey, I have this urge. I feel like I have to go. 

[00:21:02] Jonathan Wolf: Will tells us that gas and bloating is a tell-tale sign of constipation. Almost a hundred percent of people who are constipated will experience gas and bloating, but other symptoms include a distended belly.

[00:21:14] Will Bulsiewicz: nausea, loss of appetite, fullness after meals, people often will have a crampy abdominal pain, and that discomfort can actually come in waves. And it can be extremely intense. Like some of these people think it's so intense that they have some sort of surgical issue when in fact it's just constipation. And you know, the other thing too is fatigue. So this can be another common symptom of constipation. 

[00:21:37] Jonathan Wolf: And so if we are looking at all those problems, how do you actually diagnose constipation?

It sounds like it's such a sort of broad mix of things. 

[00:21:45] Will Bulsiewicz: It is a broad mix of symptoms, but you know, the first step is that you have to prove that the person is actually retaining stool and backing up. And the perhaps easiest way to do this is with an imaging test. So this could be an an X-ray or a CAT scan, or there's a test called a Sitz Marker study.

But the important point is that even though you can demonstrate that a person has constipation with these tests, you can't prove what the cause of the constipation is based upon that test alone. And so there are many potential causes for constipation beyond just slow movement of the intestines. And over the last two decades or so, we've developed new testing that's pretty impressive and allows us to really get to the heart of understanding these problems.

[00:22:35] Jonathan Wolf: There are a few ways to treat constipation. When you first notice the signs and it doesn't necessarily mean taking pills. 

[00:22:41] Will Bulsiewicz: From my perspective, you know, it's sort of common for people to head straight to the pharmacy to pick up whatever sort of medication is available to treat their constipation and, and sadly, in many cases in our healthcare systems, the doctors will recommend these things.

But I personally think that we need to start with diet and lifestyle first. This should be our first step, and there are simple steps. Such as increasing our intake of whole plant foods, where by doing that, by increasing our whole plant food intake, we are actually increasing our fiber intake. And when we reduce our ultra processed food intake in combination with this, we ultimately are guiding ourselves towards a number one, more microbiome friendly diet.

Number two, a dietary pattern that can improve the health of our bowel movements. Including, potentially resolving mild constipation. So I kind of feel like, whoa, whoa, whoa. Let's not jump to the medications first. We may get there.

[00:23:43] Jonathan Wolf: And one of the things that I've been really struck at looking at all the members who go through the ZOE program and they report back on sort of changes in their health is there's a lot of people who've been reporting significant reduction in constipation.

And I'm struck by that because it wasn't something that any of the scientists were talking about as they were working to optimize this guidance. So it's a sort of really for me, really unexpected byproduct. All of these people are following these programs personalized to them, focused really on their long-term health.

And then they're coming back quite early on in this program saying, well, like, wow, like my constipation has got much better. I guess are you surprised by that and, and can you help to explain why that's happening? 

[00:24:25] Will Bulsiewicz: So I was gonna say, I'm actually not that surprised to be totally honest with you. And what's interesting about it is that the ZOE program was developed using the microbiome and looking at things like blood sugar, blood fat.

We're attempting to improve the health of the microbiome. Now these microbes, they are connected to our bowel movements. To our digestive health, our digestive function, and to all these other facets of human health. And so, when we develop a program intended to sort of improve the gut health towards blood sugar, blood fat, we're simultaneously improving the health of these microbes in general.

And this leads to these benefits that we see that like we can say it was unintended - this is an unintended benefit - that a person has better bowel movements and improves their digestive health and reduces their constipation. But this is exactly the way that this is supposed to work, which is that when we enhance the quality of our diet and we enhance the health of our gut, we will see better bowel movements. We will improve constipation, we will have less symptoms, and that's a beautiful thing. 

[00:25:31] Jonathan Wolf: There, we see the power of the microbiome once again. So obviously, gas, bloating, heartburn, constipation are all clear signs that something's wrong. A healthy gut should be free from these digestive problems and have a good balance of microbes.

So what do we know about the other signs of an unhealthy gut? 

[00:25:51] Will Bulsiewicz: To be clear, everyone has occasional digestive symptoms. I mean, particularly if you have one too many pints and you load up on the spicy, greasy food. But really what I'm talking about are chronic symptoms that are occurring weekly or even more than that.

There are many ways that they could manifest. As a clinician, my first question to the patient is very simple. How do you feel? 

[00:26:10] Jonathan Wolf: Actually the same question my therapist asked me. So I, I like that it's getting straight to the point. So if you're looking, for symptoms in this case, and I think you said, look, these are symptoms where you're having this at least once a week, that's where you're starting to, say this is not just because you ate something that you're not used to, but this is sort of really starting to be something you might talk to a doctor about.

So what are the sorts of symptoms. That, you know, I or any of the listeners might say, Hey, that's a manifestation of an unhealthy gut.

[00:26:36] Will Bulsiewicz: Sure. I mean, of course it could be digestive symptoms. So some of the classic digestive symptoms would be gas, bloating, constipation. But you know, it's important to understand that it also goes beyond the gut.

So it could be issues with sleep, skin changes such as rashes, sugar cravings, or even unexplained mood disorders. I always think about the whole person. You have to think about everything, not just the gut and the gut symptoms. 

[00:26:59] Jonathan Wolf: Then after your doctor has asked you how you're feeling, it's time to talk about a topic that a lot of people want to avoid.

So you've asked this first question, what's the next thing that you're gonna ask our sort of hypothetical gut patient who's coming to see you. 

[00:27:13] Will Bulsiewicz: The second thing, it may be a bit taboo for a lot of people, but as a gastroenterologist, I found this to be incredibly important, and that's bowel movements. 

[00:27:22] Jonathan Wolf: So Will, we've talked about this before. You know normal people when you first meet them, you don't ask them how often they go to the toilet. In fact, it's something that lots of people don't even want to talk about with their family or their partner. So why do you have to ask them this?

[00:27:39] Will Bulsiewicz: Cardiologists look at blood pressure and heart rate. As a gastroenterologist, I look at bowel movements.

This is my vital sign, and I see it as a window into digestive health when things aren't working the way they're supposed to within our gut, it's typically gonna manifest in the toilet bowl. 

[00:27:55] Jonathan Wolf: And so what kind of things do you talk about with patients, Will? 

[00:27:57] Will Bulsiewicz: So the first thing that I look at is rhythm. Very similar to the heart.

If you knock it off rhythm, then things just get disrupted and they don't work the way they're supposed to. So we're supposed to have a cadence and that means that we should be pooping on a regular basis. 

[00:28:10] Jonathan Wolf: And as well as rhythm, you should well feel good afterwards. Like you are sort of strutting out of the bathroom with a smile on your face.

Not like you've just done, you know, five rounds in, in the boxing ring. 

[00:28:21] Will Bulsiewicz: Nah, certainly not five rounds. Maybe we're not supposed to say this, but you're allowed to feel good. You're allowed to feel well after a good, healthy evacuation. You know, as a medical doctor, that's where I want you to be. And the bathroom experience really should be something that's positive and relaxed.

[00:28:38] Jonathan Wolf: So for a healthy gut, you want to feel good overall, and your bowel movement should be regular and easy. Then there's something known as gut transit time, and here's the point in our journey where we finally get to blue poop. Yep, you heard it right. Gut transit time is how long it takes for food to travel from your mouth to the other end.

Will, can you tell us a bit more about that? 

[00:28:59] Will Bulsiewicz: ZOE actually did some exciting research into this, Jonathan, and by simply eating food that contains this blue dye coloring and then tracking how long it takes from when you first eat that food to when it ultimately comes out the other end with a blue bowel movement, the blue poo, as we like to say.

What's really interesting about this is like, it's curious. It's cheeky. But also, it's science-based. The blue poo we have discovered is actually correlated with characteristics within your microbiome. We found that transit time can actually be a better measure, believe it or not, of your gut health, than looking at things like your stool consistency or the frequency, or even the Bristol Stool Scale.

[00:29:36] Jonathan Wolf: So if you're listening to this thinking, hang on a minute, I do have some of the signs of an unhealthy gut. Don't panic. There are things you can do. Eat a varied diet that's high in fiber. By including plenty of whole grains, vegetables, and fruit, but also eat more slowly, drink more water, and make sure you're getting good quality sleep.

[00:29:58] Will Bulsiewicz: Cutting back on all highly processed foods can be another step that people can take. 

[00:30:01] Jonathan Wolf: And if I do all of those things, do you think I would expect to see a change in my gut health if I was exhibiting some of the things that you've been talking about earlier? 

[00:30:09] Will Bulsiewicz: Absolutely. I mean, remember that, you know, it kind of comes back to this basic first question, which is how do you feel? You should feel better when your gut is becoming more healthy, you should feel better. You should see an improvement of food intolerances. You should have better bowel movements and over the long run you may be able to improve your health status in terms of reversing or improving or reducing your risk of these chronic medical conditions that we've been talking about.

[00:30:32] Jonathan Wolf: And one of the things I always love, whether it's you talking about this or Tim or anyone else, is there's a huge amount of positivity because this is an area where you're always saying, you know what? There's a power for us to make changes that can really improve our health. And I think most of the time we feel we're sort of stuck in a one way deterioration.

So like it's all like, ah, you know, my body was great when I was 21 and now it's just getting worse and worse. Or, you know, there's nothing you can do. All you do is just sort of holding back the tide. And so I think what's, what's really great listening to this is you're saying to lots of people actually you can really improve your gut health so that it's a lot better in a year's time than it has been, you know, maybe for decades, maybe since forever. 

[00:31:13] Will Bulsiewicz: I'm twice the age of a 21 year old at this point in my life, and I think I have twice as much health as I did when I was 21 years old. And that's because of changes that I've made to my diet and lifestyle through the years that have allowed me to get to a better place.

And I think it's really a message of empowerment here, which is that you are not a genetically pre-programmed list of medical conditions and health related problems, that you actually have the power through your choices to make small changes that can actually yield massive results in terms of your health.

That to me, is the important message and it's really exciting. 

[00:31:42] Jonathan Wolf: That's one thing we're really committed to at ZOE, showing you that when it comes to your gut health, you have the power. I don't know about you, but I'm really excited to see what we're going to learn in the next 20 years. 

If you enjoyed today's episode and want to find out more about gut health, why not listen to the episodes featured in today's show in full?

You'll find links to each of them in the show notes. If based on today's conversation you'd like to learn how to feel more energetic, improve your gut health, and reduce your risk of long-term disease, then you may want to try ZOE's personalized nutrition program. Your ZOE membership comes with our app that gives personalized guidance throughout the day on exactly what's best for you to eat.

Supported by nutrition coaches so you can learn how to change your diet and your health habits to be best for your biology. To learn more about ZOE, you can head to and get 10% off your purchase. If you enjoy today's episode, please be sure to subscribe and leave us a review. Or if you know someone you think would enjoy the show, share it with them.

As always, I'm your host, Jonathan Wolf. ZOE Science & Nutrition is produced by Fascinate Productions with support from Sharon Fedder, Yella Hewings-Martin and Alex Jones here at ZOE. See you next time.