5 ways relationships impact your gut health with Prof. Tim Spector

Is human contact shaping your gut health more than you realise? In this episode, Prof. Tim Spector explains how gut microbes are shared between people — through relationships, daily contact, and the environments we live in, and why this matters for long-term health.

You’ll learn how modern habits around cleanliness, parenting, and social life may be influencing your gut in ways most of us never consider.

If your gut reflects the people you live with and the places you spend time, what small change could you make this week - in your home, your habits, or your social life - that might support your gut for the long term?

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Transcript

Jonathan: Tim, thank you for joining me today.

Tim: A pleasure as always, Jonathan.

Jonathan: So you know the role. We're gonna kick off with a rapid fire Q&A from our listeners. You ready to go?

Tim: Ready!

Jonathan: Do most bacteria cause disease?

Tim: No.

Jonathan: Are we born with a fully formed gut microbiome?

Tim: Nope.

Jonathan: Is our gut microbiome influenced by who we live with?

Tim: It is.

Jonathan: Is having a pet good for our gut microbiome?

Tim: Usually, yes.

Jonathan: If we spend time with someone with anxiety, could their gut bugs make us more anxious?

Tim: It could.

Jonathan: Can bacteria from soil benefit our health?

Tim: Sometimes.

Jonathan: And finally, what's the most surprising new thing that you've learned about gut bacteria?

Tim: Well, I've known for a while how important it is for our metabolism and our immune system. But what's really struck me is the latest research, showing how important it is for our brain and our mental health. I think that's really striking, and I think this is where we're gonna be seeing some dramatic developments in the next few years.

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Jonathan: That sounds incredibly exciting and actually I'm looking forward to this whole podcast. Because obviously we talk a lot about the bacteria that live in our gut and things like eating 30 plants and more fiber. And also the way that our sleep and stress, all of these things can affect us. We're talking about something different today, which is really exciting.

Jonathan: So instead of focusing on the bacteria that are already inside us, we're gonna talk about how those bacteria get there in the first place, and I hope at the end, a bit about how we might be able to get some more of the good ones. So, Tim, when does our gut microbiome, you know, this collection of bacteria, start?

Tim: Well, since humans evolved, we've basically been passing on our microbes from one generation to another as the sort of basic core building block set. So it comes from our mothers. So when we're in the womb, essentially, for all intents and purposes, we're sterile in terms of microbes, and it's the birthing process that is so messy and dirty, and our mouth is designed to be in the right place through the birth canal that it's getting the microbes from the birth canal and the intestine so that our mouth, as we coming out, is getting full of microbes.

Tim: In the next few hours, they develop and give us our building blocks for what then carries on. So it allows the child to have sufficient microbes that they can break down breast milk and survive. And then it uses that base to slowly build up for the next few years. But it takes really about four years until we have a proper functioning gut microbiome that resembles the adult form.

Jonathan: And so when a fetus is in the womb, there are no microbes inside its gut. It's empty. And then is it just by chance what you're describing, like they pick up some microbes as they're being born, but equally well, they could pick them up over the following few weeks, or is there something more controlled about this?

Tim: It's controlled by evolution essentially. We've had millions of years that all mammals go through this birth process, and it's been designed as a way of transmitting the microbes from one generation to another into the gut of the newborn, and so it's not by chance, you know, this is basic natural selection.

Tim: That's why the birthing process has been developed in this way that as well as trying to ensure survival at the same time, it is a way of the mother passing on the microbes. And there are changes in the later stage of pregnancy in women, both in the vagina and in the gut microbiome, where those microbes are changing specifically so they can be passed on to the child.

Jonathan: So you're saying that you can actually see in the mother changes in their microbes in order to almost pass on this sort of inheritance of specific bugs.

Tim: Precisely, yes. And that's in all mammals.

Jonathan: That sounds crazy.

Tim: Yeah. But it's, you know, it just shows how important these microbes are to our survival and why it's been important for millions of years.

Jonathan: And are those microbes that passed on and the microbiome, you know, when we're just a little baby, the same as the microbiome that I would have now as an adult?

Tim: No, you'll still have traces of them, but at each stage of life, they form a particular purpose. So the ones you're getting, the very first stages are the bifidobacteria that are designed to break down breast milk and also to start the discussion with your immune system. So they're training your immune system.

Tim: They're breaking down the breast milk into sugars that you can actually eat. So they're the key things and you obviously don't need those as much when you're no longer drinking breast milk.

Jonathan: So does that mean that there are bugs that were only useful like in that first year that just sort of disappear and I don't have anymore?

Tim: Yes. Or they might go down to really low levels. So there'd be the predominant species, these bifidobacteria that are really focused on breaking down the milk products, which are highly complicated structures that we still don't totally understand, but they're broken down into the bits that the baby can then use and that sends chemical signals to the immune system.

Tim: It starts training it. What is normal food? What's an alien bug? All these kind of things start to happen so that as the baby's growing, the immune system is also learning from this interaction. And so the microbes that are being formed are also giving the baby this idea of early warning sensors about its environment. And that's the other important: it's not just breaking down the food, it's also sort of sensing the environment of that baby and whether the immune system should be worried or upregulated or calmed down.

Tim: But the early microbes are really very different to the adult, and it's not as varied as the adult one is at all. So it's really much focused on these narrow aims. So it's not a very diverse microbiome at that stage. And it's also very flexible. So you see these really massive changes just from a slight change in diet, a virus might come through, weaning produces really big changes, things that you don't see as dramatically in older children.

Jonathan: So you're describing it like a vaginal birth, right, Tim?

Tim: Mm-hmm.

Jonathan: What happens to babies who are born by cesarean?

Tim: That's really interesting. And of course in many countries that's nearly 50% of births now, and it's not what evolution had designed for us. And it means that they're not getting the normal dose of microbes into the mouth they would be getting through a vaginal birth.

Tim: So they're born much more sterile and it takes longer for them to get those microbes inside them. There are quite big differences in the immune systems of babies born naturally and through cesarean section. And studies have shown that the microbes being different gives an increased risk of allergic diseases, atopy, and get increases in weight as well in cesarean section babies.

Tim: It seems to be this effect. It doesn't last forever. So that cesarean section babies do catch up, which is nice because I was a cesarean section baby. So it's nice to have felt that I've caught up a bit, but it also might explain why I had lots of asthma and allergy as a kid, so everything is slightly delayed.

Tim: And there are some scientists who believe that you should be seeding the microbiome of babies who've had a cesarean section. This means that you should mimic what nature did and put a swab between the legs of the mother giving birth and smear the baby's face with those microbes to do that. And there's still some Scandinavian hospitals that practice this, but the studies have not been conclusive that that actually materially changes the health of that baby so far. So the jury's still out about whether you can trick the process, you know, have a cesarean section and still have that same natural birth.

Jonathan: I've experienced two births in my life, which are my own children, and I'm not a doctor. I haven't seen in my life... a vaginal birth is a pretty messy experience in terms of what I've seen.

Tim: Well, now you know why. I mean, it is designed to be messy. It's interesting, you know, so that's part of it.

Jonathan: And you were describing, I think you were quite careful about the words, but it sounds like you're saying that historically babies evolved, where not only are they getting sort of microbes that might come out of the mother's vagina, but actually they're ending up basically being exposed to like the poo of their mother as well. I just wanna make sure I'm really clear about that.

Jonathan: Which I think to me as a modern person sounds sort of disgusting and unhygienic and dangerous, but it sounds like you're saying on the other hand that the C-section, which is completely sterile and avoids all of that, means weirdly that you don't get the same set of bugs and you could end up actually having more allergies and things as a little child than otherwise.

Tim: Yeah, exactly. You're getting microbes from the vagina and the rectum, the lower part of the gut, and the fact that the mother's microbes have been changing in the last trimester precisely for that mean that, you know, that's the ones they want to pass on to the baby and this is where they get these important bifidobacteria from, that then they can use to train the immune system and break down the milk.

Jonathan: When I think about how much we are really careful about cleanliness, when babies are very little for very good reason, I can't really imagine a doctor replicating sort of the experience that you have through vaginal birth. You were describing trying to expose the baby to these bugs, but

Tim: most doctors have not been very keen on that. And particularly microbiologists worried that you'd be giving them potentially a bug to the baby. So there might be some streptococcus or something that you don't want to give them, which is slightly counterintuitive on the one hand because say, well, that's what nature designed.

Tim: But you're also saying that modern science is saying, well, you could give it so most doctors are anti it. And we still don't have the real definitive science to say which is actually best. I mean, it's obviously natural delivery is always gonna be the healthier, better option, as is breastfeeding. And you know, the best of both worlds for the baby's gut is to have a natural birth and breastfeed.

Jonathan: And whenever we talk about this, I think about like how hard it is to be a mother and all the pressure about doing everything perfectly. So I think I also heard you say like if you do have a C-section, then in fact in the longer term your child will be fine and that this sort of balances out over time, Tim, is that correct?

Tim: Yes. So we've done some studies, we looked at our twins, for example, their microbiomes of those that had C-sections 40 years before, and those that hadn't, haven't shown any differences in their adult microbiome. So by that time it's got out of the system. So I think it's only really the first few years of life that you are compromising the kid, and that's why you might get more weight gain, more allergies in those first few years. Immune system is not working as well as nature intended.

Tim: It could also be something to do with the antibiotics you're getting often routinely with cesarean sections that just slipped in, you know, by the anesthetist without really much discussion. As you know, you know, antibiotics have their problems and a lot of children are now getting many courses of antibiotics in those first few years without the mother being given full understanding of what's going on. Because we treat them as having no real downsides. Although they can save life, obviously, they also come with a little cost to our immune systems.

Jonathan: And so if I have repeated antibiotics as a small child, which was definitely my experience because I was growing up in the States and I think that has been and continues to be even heavier use in the US that can have an impact on the microbes that I end up having when I'm an adult.

Tim: They haven't definitively shown that. They've shown it in mouse models and they've shown it in epidemiology as well as you can do. It's very hard to follow people over that length of time with those detailed records, but in general, that is true. But there might be different responses of people. So on average, yes, that's gonna be true, but some people might be able to cope with antibiotics without any problems. Others were very sensitive.

Jonathan: Is one course of antibiotics in my childhood gonna have the same impact as having, you know, 20?

Tim: No. The more courses you have, the worse. But there's also some evidence from animal studies that if you have small amounts of antibiotics, say from antibiotic fed meat, that can also have a negative effect on your gut microbes.

Jonathan: So we talked in a way about how you might not get the ones that you might have otherwise, but how do I get new ones? So you said that my microbiome is actually very simple as a baby when I'm built to be breastfeeding. Or if I am breastfeeding. But we know that once you're an adult, it's very complicated and there are all of these different species. Where do they come from?

Tim: Well, they come from all around us. They come from other humans. So when your baby's picked up by someone where it's a mother or a family member or a friend, they will be transmitting their microbes. Which might be on their skin from their saliva, but also gut microbes in tiny amounts all over.

Tim: So babies like sucking things. So if you put your finger in a baby's mouth, they're gonna be getting some of those microbes from other people. And that's generally how they gain these microbes slowly over time and it seems to me the more people they come into contact with, the more different microbes they're gonna be getting.

Tim: And the environment also plays a role. So some of these will be in the air, some will be on surfaces, and there's a difference between sharing microbes in the mouth and sharing microbes in the gut interestingly. So we did this big study of transmission. It was led by Nicola Segata's team in Trento.

Tim: Looked at tens of thousands of people and looking at relationships and showed there was a clear difference in how you gain your microbes in your mouth, which is actually from, put it bluntly, a lot, everyone's spitting in micro doses all around. Babies don't get all their oral microbes from their mother. They get it from everyone else in the family spitting at them. But this tells us what's happening all around us.

Jonathan: So Tim, is that a bit the equivalent of how I get a cold? I'm thinking back to like what we learned in COVID. You know, if you are in a room with someone else who's sick, after 15 minutes you get the virus. Is there something similar in this case about my mouth bacteria?

Tim: Yes. Yes. Even as we are speaking here, there's probably a sort of cloud in the middle here of these, you know, little microbes that we are exchanging, whereas we are much less likely to be exchanging our gut microbes, Jonathan, you'd be pleased to know.

Jonathan: Well, what I'm thinking, Tim, is that I now want to step back away from you, but unfortunately, I need to stay near the microphone, so I'm sorry.

Tim: So we probably need to touch more intimately to swap our gut microbes, and that's why babies share most of their gut microbes with their mother for the first three years, and that drops over time. But it's a really close relationship, whereas the oral microbiome is not shared as much with a mother. It's the same with everyone in their family.

Jonathan: I think you're saying that the microbes that are in our gut are not the same species of microbes as might be in our mouth or might be, I don't know, on things that are just out there in the environment. Is that right?

Tim: Yes. Every microbe has a particular environment it likes. So the ones that are sitting on this desk here are ones that like oxygen. They might also like our skin, so they might be able to hop onto our skin and like that. The ones in our mouth will have to be certainly adapted to the acidity of our mouth and be able to cope with saliva.

Tim: And they're very different, but also quite like oxygen, because there's a fair bit of oxygen going on. Whereas the ones in our gut generally don't like oxygen and like, again, different conditions. So when we're swapping them, they've gotta be swapped to like an equivalent place.

Jonathan: So we need to get microbes that actually only really are happy living inside the gut without air, which makes me think, well, that is relatively hard to get those microbes onto me as a child or as an adult compared to the ones you're describing for my skin which like the oxygen is, is that right Tim?

Tim: Yes. So very different. Talking about in your mouth, on your skin, in your gut. They're all important though, so we mustn't just focus on the gut. Skin microbes are incredibly important for preventing skin diseases and keeping us healthy and our oral microbiome is really important, fighting tooth decay and preventing heart disease, etc. So all of these things are important, but we have to think of them slightly differently.

Tim: And there are a few oral microbes that can live in your gut. So they can obviously pass through and there's a overlap between the mouth microbes and those in the small intestine as well. But each one has a little niche where they're happiest. Some can survive, but they're not very happy.

Jonathan: So we get our oral microbiome basically even just being around other people talking to us. And I now have this vision that, you know, if you're in a like a Mediterranean environment, it's much better than if you're in, I don't know, Finland. And in my experience, they're a bit quieter and more reserved. Like the more that people around you like gesticulating and talking wildly, the more oral microbiome sharing that's going on. Is this what science says?

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Tim: Socially, might be surrounded by, you know, 10 naked people in a sauna. So there's different ways of combining socially, but yes, in general, the bigger the family group or the social group, the more you're gonna be sharing your microbes.

Tim: And this is what the science is telling us as well. And it comes back also to this idea of the hygiene hypothesis that the larger the family, the less allergic diseases, less atopic diseases. And this is from an epidemiology colleague of mine, David Strachan, who had worked out from looking at thousands of families that if you were either the last born in a series of kids or that it was a large family, you were less likely to get allergies than if you're a small family or you're the first born and it's this exposure to bugs and dirt and everything else that was basically helping your immune system.

Tim: So it's this link between the more microbes you've got, the more diversity of microbes means that you have a tougher immune system, which means that it's much better trained, so it's not gonna react and give you peanut allergy or asthma or eczema.

Jonathan: So how am I picking up my gut microbes from the world around me as I'm going from, you know, one years old to today?

Tim: We don't know precisely, but there've been studies done to show that wherever people are touching surfaces, you'll find some gut microbes. Not as many, but if you go to the bathroom, studies have shown that you can find gut microbes all over the place. We are literally surrounded by microbes everywhere, and so it might just be by touching a surface, putting your hand in your mouth, drinking a coffee.

Tim: Generally between people, you usually need more intimate contact. So that's why we find that couples living together are gonna be much closer in their gut microbes than, say, siblings living apart.

Jonathan: Say that again. So you're saying that you can tell whether or not, you know, I'm living with my wife or one of my siblings versus if we are not living in the same place from my gut microbes.

Tim: Yes, we'd be able to tell. Whether you have specific strains that you and your wife are sharing as opposed to you and your sister, for example. Now with the latest science, it's quite easy to do, and that's what we did in our nature study. So by looking at the precise strains, which are very, you know, one below species level, we know this one has been shared between people.

Tim: And so that's how we know that these effects are really real. So if you wanna show your gut microbes, you cohabit with someone. Ideally, you know, you're in a close or sexual relationship, but it's the physical closeness that's important. And as soon as that starts to move away, you lose it. And that closeness is more important than genetics. So a couple living together are gonna share more strains than identical twins, unless those identical twins are sharing a bed, which is unlikely.

Jonathan: So there's like a big sharing of microbes if you have a sexual partner.

Tim: Yes, exactly.

Jonathan: And is there still a big sharing? Like if you're in a household and I'm, I guess I'm also thinking about kids, is that also going on?

Tim: Yes. I mean, the mother child one is the strongest of all. That starts to fade away after the age of five and gets less and less. Then you've got people living in the household together. And then as those relationships get more distant, then it starts to fade apart.

Tim: But you can find differences. We found strains that were similar in people living in the same village. They weren't sexual partners or anything. So just being in the same community, you will have these same gut microbes in common, these particular strains. So your own gut is reflecting your environment and your social group.

Jonathan: I love this idea that my microbiome, which is sort of like an organ, right? That's how you describe it to me, Tim, like it's like having my liver or something is almost a snapshot of all the people that I've met over time. There's something sort of really cool about that, although there are some people I've met who may be a bit unsavory, so perhaps, you know, maybe you'd like it to be more selective. We've been talking about all these good gut bugs that you pick up to like build out an adult microbiome. Can you also pass on the bad gut bugs?

Tim: Absolutely, yes. Most of these studies are in animals. Rodents and they've done lots of transmission studies to show that you can do this. And the first ones really showed that you could transmit things like obesity.

Tim: So you took an obese animal and you then took its droppings and you put it into the feed of another mouse and it would gain weight. So that was the first sign this was happening, although those effects were quite small. And what's been interesting recently is that the evidence is really building that you can take rodents with mental health issues.

Tim: They get very anxious and you take their droppings and you can transmit them and put them into another mouse that was normal and you make that mouse anxious. So that's probably the best evidence we have that transmitting microbes can actually alter the mental health of someone else. And that's quite mind blowing really to think that.

Tim: You know, if in your family you're surrounded by all these anxious folk and you are swapping gut microbes, there is the potential that some of those microbes could be working in an unhelpful way on your own mental health. The opposite could also be true. So if you, if with someone who's really happy and really relaxed, hopefully you wanna be getting their microbes as well. And it's still a bit unclear about which microbes work better. And I think it's gonna be very personalized to say, are you more like to be a recipient of them or you more like to be a donor of them, that we don't know in humans yet.

Jonathan: We do now know for the first time sort of what the good bugs and the bad bugs are. Is that right Tim?

Tim: Yes. We're starting to understand that and I think our recent ZOE paper in Nature was one of the first to get a comprehensive ranking score of healthy bugs and unhealthy bugs. But we haven't done it for every disease and we haven't really yet done this for mental health, you know, and how it affects the brain.

Tim: So we are just starting this journey, but I think this will be really interesting because we'd all love to be able to say, well, how can I get all the good bugs and how can I, some will fight off all my friends' bad bugs and just take the good stuff.

Jonathan: And if I, you know, meet someone once or date someone for a week, is that gonna make much of a difference?

Tim: I think the answer is, it could do. So say you are intimate with that person, Jonathan. You would definitely be swapping oral and gut microbes with that person. And if it turned out they were giving you some that had a niche in there that you know, their bugs could fill easily, then yes, that would change your microbes permanently. Perhaps the healthier you are, the less likely it is to be disturbed by the other person.

Tim: The studies definitely show that people living in rural communities have a more diverse, healthier gut microbiome than people living in cities on average. We also know that if you spend the first few years living in a rural environment and farms, etc, your immune system is much better. You're gonna get less allergies and problems. If you've been brought up in a farm and then you move into a city, it seems, you know, you're not really protected long term, so you perhaps have to live there more permanently.

Tim: You lose those microbes as you go into a city. So that probably means that if you move from a city into a farm within a few years, you would start getting the benefits of that. And we know that you are getting the benefits of many more beneficial microbes. You're getting microbes that are coming from soil microbes that are coming from animals, all these things that you are not getting in cities where in the cities you're just getting microbes that love dry conditions, you get more bad bugs, more what they call pathogenic microbes when you swab, you know, houses in cities than you do in the countryside.

Tim: So it is quite different, but we don't really yet know how we could use this as therapy. But definitely whenever you can, it shows us we should be going out into the countryside, hugging some trees, doing some gardening, you know, getting dirty,

Jonathan: Just going out into nature, getting your hands dirty. Why is that gonna help me?

Tim: You'll be exposing yourself to microbes that are in the earth and the soil. And some of those are also found in food. So in vegetables and other things like this. So some of them might be able to take hold inside your gut. This is still, we don't know very much about the interaction between all those different soil microbes and the human ones.

Tim: It's all still work in progress, but it is really interesting that people who do spend a lot of time playing with soil or gardening do have better mental health than people that don't. And it's one theoretical possibility that a lot of this is due to some of these microbes that is improving their gut health, which then feeds back into their brain.

Jonathan: And does that mean that when we're outside in the environment and or gardening or whatever, we should ignore all the advice that I feel that we've had pretty much for the last 50 years, which is like, you must wash your hands all the time after doing this and never touch your mouth. Because actually it's what you're saying, it's not just being out in the environment, it's getting my hands dirty and ultimately putting this in my mouth, so that ends up in my gut, is that almost what has to happen if I'm to get the benefit?

Tim: It does. Yes. Obviously, you're to select which bit of earth you are taking, whether, you know, it's not in the local park where you know your dogs have been having a poo. But generally, yes, if it's in a healthy space, you shouldn't be worrying about this. And you shouldn't, and you should be encouraging your children also to get dirty without being obsessive about it. And there's quite a lot of evidence that houses that you know are over sterile and do obsess too much about that side of things have a negative impact on children's health. Their immune system being over sterile is bad.

Jonathan: I think that's quite a surprising message. Right. We are generally told that we need to keep the environment of our children really clean and there are a million products sold. I remember when my kids were really little that you would like spray on all your toys. And sterilize them and wipes. And you're saying actually that that's not just unnecessary, but might even be harmful.

Tim: I think that the advice to sterilize everything is outdated. Now, for every one infection that you might prevent, which we extremely rare, you could actually be causing more longer term problems.

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Tim: So it's getting the risk and benefits properly balanced. But there were studies of showing randomizing people with toddlers and dummies when the dummy fell out as it invariably does. They sterilized it and put it back, and another one where they just put it back in the mouth without sterilizing it. And allergy rates were lower in the ones that they hadn't sterilized. So sometimes doing less is better.

Jonathan: And I think that's really surprising. Could you just talk me through what's going on, therefore? So why is it that exposing your children to like the dummy that's fallen on the floor, why on earth would you end up being healthier as a result?

Tim: The current theory is that the dirty dummy that gets put back in has extra microbes on it that the baby has not been used to. And this ends up going into the mouth and some of them going down into the gut, basically educating the immune system that it doesn't have to worry about these microbes.

Tim: These are fine, there are small amounts of it. They're not gonna do me any harm. I don't have to overreact. And the more times this happens, the more you are like educating, training the immune system so that it doesn't overreact and fight back. Whereas the sterile dummy kid is hardly getting any microbes. The immune system, you know, is just waiting around for something to do and then when it gets hit with, you know, some cow's milk or some peanuts at some point it then overreacts. So that is a simplistic way of looking at it, but it's, I think we're moving into this idea that, you know, often eating and eating microbes is a way of training our immune systems for the rest of our lives. And if we are too protective, that's why we end up with this epidemic of allergic diseases.

Jonathan: That's all absolutely fascinating. I'd love to talk about how we can use all of this to support our health and maybe just start like with me. So I'm constantly trying to get more of the good bugs inside. Um, and Tim, as you know, like when I first started at Zoe and we reanalyzed my samples, I had about 20 of the 50 good bugs.

Jonathan: And about two and a half years ago, I'd grown that up to 38. Following all of your advice about what to eat. And then I took these like really heavy antibiotics after I smashed open my toes and we retested and I'd gone down to six good bugs and I've been steadily working and eating as well as I can.

Jonathan: And I've got it back up to 23. So it's a lot better than six, but it's not only half of the 50 good bugs that you've identified. So my question is, how can I get more of the good bugs? In my gut, and I'd love to talk about, you know, some of the different practical things that I might do and just listen to some of the things you've said. For example, like, should I go and get myself a dog?

Tim: Yes, I think you should actually. The science does support having a dog. There have been several studies now showing that dog owners have more diverse and healthier gut microbes than non dog owners, and I used to be very rude about people who had cats.

Tim: I was talking about this five years ago, but there've been some recent studies also showing that cat owners are also healthier and that you can get some of the microbes from cats into your gut itself. Now, we share more closely our gut microbes with our dogs, they're more interchangeable 'cause our diets are similar. We're both omnivores, whereas cats are rather different than anybody, meat eaters.

Tim: So we don't know entirely why cats are beneficial, but it could just be that they're bringing in lots of stuff from the garden. All kinds of other microbes are there. So anyone listening, I'm sorry about being rude about cats in the past, I apologize. But you know, science moves on. So a pet is one thing. Definitely. You should get Jonathan. Yes, I would suggest you do a bit more gardening. Do you like gardening?

Jonathan: I do like gardening.

Tim: Get dirty. Do that more often. Go for walks in parks more often. And of course, avoid doctors and antibiotics whenever you possibly can.

Jonathan: What about the food that I eat. So clearly, I mean, one of the things that has happened is that I have expanded that number a lot from when I first had those antibiotics. Are there live microbes also on the food? Because we haven't really talked about that yet today.

Tim: There are live microbes on food. And you may remember, Jonathan, we published this study on vegans, vegetarians, and omnivores, a really big study. And it clearly showed us that each of those different groups had a certain signature you could see in their gut microbes. So the vegans and the vegetarians were showing microbes related to the plants they were eating.

Tim: These are species you probably won't have heard of, Enterobacter and Citrobacter, that you getting on the plants. You can then detect in your stool samples. So they're lasting all the way through, and they're different to people who are mainly on meat-based diets or processed diets. So your diet can in a way bring in your garden into your health in the same way that meat eating and gardening.

Tim: The more plants you eat, the more of these you're gonna be getting in your diet. So that's why diet is such an important part of improving your health as opposed to these other lifestyle measures. It's definitely the predominant one. So more plant-based foods. Ideally if you can have organic, you're gonna get slightly more of these and less of the pesticides on them.

Tim: That'd be fine tuning that diet. And if you know the produce is coming from, say, an organic source that you trust, don't worry about trying to scrub every last inch of earth off it. That earth will probably doing you some good as well. So they're sort of classical things. Plus the 30 plants a week are quite crucial to this.

Tim: Same rules about giving polyphenols. So you are brightly colored, brightly tasting plants to feed any gut microbes that are there. And then fermented foods trying to get three portions of fermented foods in your diet. All of these will increase your good bugs relative to your bad bugs as well as all these lifestyle measures.

Jonathan: And if I were to choose to live with someone who's got a much healthier gut microbiome. Let's say I can find someone like you, Tim, who's got almost all of the 50 good ones.

Tim: I'm not available, Jonathan, ever.

Jonathan: Yes, but let's say I could, if I was, let's say I could, and in that situation, would I slowly improve my health, even without making any changes to my diet?

Tim: Probably. I mean, the data we have is at one point in time we haven't followed couples up together. But my guess is that's what would happen. I dunno how much you would improve, but you would definitely improve. So it's definitely worth picking the best partner you can get the healthiest partner and maybe that's all part of, you know, why we select mates because we want them to be healthy.

Tim: But it's also a reason that if you are improving your diet, you also want to improve the diet of your partner as well because they can have also a negative effect on you. So you want them as healthy as possible mentally and physically.

Jonathan: And I'm thinking now about the opposite, which is, you know, loneliness. And we've had a number of really interesting podcasts with scientists explaining that sort of living on your own and lack of social interaction has like a really negative impact on your health. And I'm thinking out of this conversation that it's also likely to have a negative impact on my microbiome. Is that right?

Tim: Strangely, they have done studies, and we did some of this as part of this transmission paper, saying that people that live in small groups or have very small network of friends or living on their own had on average worse microbial health than people that had lots of friends or lived in a large community.

Tim: So it looks like at least some of the idea that loneliness is bad for your health, your mental health and physical health, you tend to die earlier if you are lonely, could be due to the partly to the effect of on the gut microbes as well.

Jonathan: And so if I'm listening to this and I, and I am living on my own, what are the, like the key actionable advice that you would give to someone like that in order to sort of maximize the health of their microbiome?

Tim: I would say try and join a club where you meet people, whether it's a walking club, you, there are gardening clubs you could do. So you get out and you are, have an allotment and you can meet other people. You want to be going for walks in parks, you want to be getting outdoors more, so you don't wanna be stuck in indoor in air conditioning.

Tim: You want to be opening your windows all the time, and you want to perhaps go to the pub more socialize, go to cafes, try and get a range of people that you can meet up with and this will help your mental health and your gut health.

Jonathan: So it's interesting that what you're describing is almost the same advice as you'd give for someone if you were just thinking about sort of their mental health and the implications of being lonely. Tim, I'm sort of struck by how much like the right thing to improve, you know, your microbiome access bug feels almost like the same thing to live a half year life as a human being.

Tim: Exactly. I think what we're seeing is a real confluence of these ideas that the same advice to avoid depression and loneliness is the same advice you would give to someone to increase their lifespan, longevity. And we've talked about Blue Zones and how people in those zones are in these large communities. They're never lonely, you know, there always interacting with other people. And then, you know, the missing link is our gut health and our microbiome and they're all coming together.

Tim: You know, the advice is virtually always the same, but for different reasons. And I think this is where the science is really helping us understand. Because it must make it much easier to take action with advice when you understand the base scientific basis behind it.

Jonathan: One of the things I'm struck by is how much you've talked about cleanliness in one way or another, and I'm also struck by, you know, this story you told me a while ago about visiting this tribe, the Hadza, who were hunter gatherers you said, and also this work where you've described that the microbiomes that we have today are just completely different to the sort of microbiomes that human beings had before, like running water and soap.

Jonathan: Is there almost like two different ways of living as human beings the way that we would've done until very recently where there was no soap and washing our hands. And then there's the world that we've been in after this. And what does that mean for us?

Tim: Well, I think there's a halfway house, I think. There are groups like the Hadza that live perfectly healthy without soap and water, but as soon as those groups get into big cities and you end up in slum situations, you end up with terrible dysentery and childhood death, etc. And what we've done in the West is go to an extreme where we're giving everyone antibiotics, we're sterilizing everything.

Tim: We're having food out of plastic, sterile containers, and we're not being exposed at all. And I think the sweet spot is somewhere in the middle that, you know, we take the learnings from both and we say, okay, well let's do enough so that we are not gonna get salmonella and dysentery every time we're eating.

Tim: But at the same time, we are maximizing our good bugs. We're not killing them off. Now that we have this new knowledge that we didn't have 20 years ago, you know, we're acting in a much more sensible way. So I think we can still realize that having running water and basic sanitary conditions, washing your hand after getting the toilet is absolutely still essential for our health, but not be obsessing so much about all kinds of sterility so that we remove it from helping our gut on our immune system.

Jonathan: So like a lot of things, somehow, it's not that we're doing things wrong, but maybe we've taken them too far or a bit like antibiotics, as you said, like it saves so many lives, but it doesn't mean you should just sort of pop it each time you have a sore throat. Because it does turn out that it has disadvantages as well.

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Tim: Exactly. So we went too far down that road. Now we just have to have a bit of a correction. And it's not like we're gonna throw away antibiotics. We'll still use them, but we should just be realizing that they have a downside and we should still sterilize some things. But just realize that if you overdo it, there's a downside. So it's just being sensible and realizing that microbes, basically, most of them are our friends, and we don't want to kill them all off because our body, our immune system, our physical and mental health absolutely depend on them.

Jonathan: Amazing. Tim, thank you so much. I think it was really interesting to understand. I think in part how you know the science has been moving on and your understanding of things is different. So all the cat owners on the podcast can be feeling much better. The thing I'm most struck by is that if you want to actually exchange the most bugs, then you're gonna do that with a sexual partner.

Jonathan: But if they have bad bugs, that could actually mean that you're gonna put on weight or even become more anxious. So, you know, you really are sharing this sort of invisible world, which is extraordinary that we now understand that our mothers are giving us this like parcel of microbes at the point that we are born and changing their own microbiome to give it to us at the point that we're born.

Jonathan: And that therefore if you have a C-section, you know, have more risks of things like allergies as a child, and that indeed if you take a lot of antibiotics as a child, this has a long term impact. I'm really struck by your view of cleanliness that it matters if you're living in a city, otherwise you could get some infectious disease.

Jonathan: But actually we've gone too far and that you said that there were these studies where they looked at kids where if when they drop the dummy on the floor, they just put it back in their mouth, they actually end up healthier than if you're sort of sterilizing that each time. And so we've sort of, again, sort of got too far in terms of not allowing them to ever get their hands dirty.

Jonathan: And then the other thing I'm struck by is we talk a lot about the gut microbiome, but today you've been talking also about the importance of the oral microbiome in our mouth and our skin microbiome and that they're all completely different. So you can't, it's not the same bug. So you could have a good gut microbiome, but a bad skin microbiome. And so, you know, the sort of, the advice I've been talking about is, is to access all of these. But then pragmatically, what I took away from this was I need to get a dog. And then apparently the dog's gut microbiome shares more bugs with me than a cat. So cat seems okay, but dog is better.

Jonathan: Start gardening. Because not only is it good for my general mental health, but maybe the microbes I'm gonna exposed to help there. Visit friends. So if you're not living in a big extended group with lots and lots of other people, then you wanna be out and with other people. Because that's about exposing this. And give them a hug.

Tim: Give them a hug.

Jonathan: Give them a hug, which is good advice if you are really English like me. So yes, like have some interaction, get out into nature and that's again, it's not just because you feel good in five minutes from that better sense. But you're saying there's also it's exposure to these microbes that the food we matters.

Jonathan: And a big part of that is like eating these 30 plants to feed maybe the small amounts of microbes in my gut, but also there actually will be microbes on the food and don't feel you obsessively have to strip everything off because in general those will be, will be healthy. Keep the window open because you said if the air con's on and the windows closed, actually I'm gonna be exposed to a lot less.

Jonathan: And then finally, don't obsessively clean around the house because actually most microbes are our friends, not our enemy. And if we sort of reduce this sense of being at war with them all, we can actually not only be healthier, but it sounds like have better mental health.

Tim: You got it.