5 ways relationships change your gut health | Prof Tim Spector

0:00Welcome to Zoe Science and Nutrition, where world-leading scientists explain how their research can improve your health.

0:13Strep throat, food poisoning, pneumonia, all examples of nasty microbes that spread easily from person to person. But not all bacteria that spread between people are bad. Some can actually transfer health benefits. Good microbes that live in our gut, skin and elsewhere can also be transferred from other people and the environment around us. So how can healthy gut microbes be transmitted? What are the potential benefits? Is a healthy gut microbiome contagious?

0:46Today I'm joined by Professor Tim Spector, a leading expert on the gut microbiome, one of the world's top 100 most cited scientists and my scientific co-founder here at Zoe. In this episode, Tim will help us answer these questions and explain how to maximize the benefits of sharing good microbes with friends and family. Tim, thank you for joining me today. A pleasure as always, Jonathan. So you know the rule. We're going to kick off with a rapid fire Q &A from our listeners. You ready to go? Ready. Do most bacteria cause disease? No. Are we born with a fully formed gut microbiome? Nope. Is our gut microbiome influenced by who we live with?

1:31It is. Is having a pet good for our gut microbiome? Usually, yes. If we spend time with someone with anxiety, could their gut bugs make us more anxious? It could, Jonathan. Can bacteria from soil benefit our health? Sometimes. And finally, what's the most surprising new thing that you've learned about gut bacteria? 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 going to be seeing some dramatic developments in the next few years.

2:20That 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 these things can affect us but we're talking about something different today which is really exciting So instead of focusing on the bacteria that are already inside us, we're going to 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, this collection of bacteria start?

2:59Well, 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're coming out, is getting full of microbes. And in the next few hours, they develop and give us our building blocks for what then carries on.

3:47So 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. 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 that 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 it's controlled by evolution essentially we've had millions of years that all mammals go through this 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.

4:45And so it's not by chance. This is basic natural selection. 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. 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? Precisely, yes. And that's in all mammals.

5:29That sounds crazy. Yeah, but it just shows how important these microbes are to our survival and why it's been important for millions of years. 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? 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 bifidobacter 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.

6:14They'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. So does that mean that there are bugs that were only useful in that first year, they just sort of disappear and I don't have any more? Yes, or they might go down to really low levels. So they'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.

6:53And that sends chemical signals to the immune system. 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 piece. 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. But the early microbes are really very different to the adult.

7:34And 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. So you're describing there like a vaginal birth, right, Tim? Mm-hmm. What happens to babies who are born by cesarean? 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.

8:18And it means that they're not getting the normal dose of microbes into the mouth they would be getting through a vaginal birth. So they're born much more sterile and it takes longer for them to get those microbes inside them. And 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 it seems to be this effect doesn't last forever so the 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.

9:11But it also might explain why I had lots of asthma and allergy as a kid. So everything is slightly delayed. 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.

10:00I've experienced two births in my life, which are my own children. I'm not a doctor. I haven't in a vaginal birth is a pretty messy experience in terms of what I've seen. Well, now you know why. I mean, it's designed to be messy. It's interesting, you know, so that's part of it. 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.

10:31I just want to make sure I'm really clear about that, 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. 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 bifidobactors from that then they can use to train the immune system and break down the milk.

11:17And 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 most doctors have not been very keen on that, and particularly microbiologists. They're 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 you're saying, well, that's what nature designed.

11:48but 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 obviously natural delivery is always going to be the healthier better option as is breastfeeding and you know the best of both worlds for your the baby's gut is to have a natural birth and breastfeed. The worst is to have a cesarean section and bottle feed. Then you get more extreme differences in the microbiome. And whenever we talk about this, I think about how hard it is to be a mother and all the pressure about doing everything perfectly.

12:30So I think I also heard you say, 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? 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 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.

13:10The immune system is not working as well as nature intended. It could also be something to do with the antibiotics you're getting, often routinely with cesarean sections. They're just slipped in by the anaesthetist without really much discussion. As 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.

13:46And 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? They haven't defensively 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 going to be true.

14:21But some people might be able to cope with antibiotics without any problems. Others are very sensitive. And is one course of antibiotics in my childhood going to have the same impact as having, you know, 20? 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. 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.

15:00But we know that once you're an adult, it's very complicated. and they're all of these different species, where do they come from?

15:10Tim Spector:If we say hormones, what's the first thing that comes to mind? Probably your reproductive system or maybe your thyroid? We're going to guess you're not thinking about your gut. Well, you should be. It's a hormone factory. It produces some of the most important hormones for our overall health, like ones that regulate our metabolism, appetite and energy levels. All your hormones together function like an orchestra, each playing their own part to contribute to a symphony. When your gut health suffers and your microbiome is disrupted, it can throw the whole orchestra off. The good news is that tuning things up is helped by your diet.

15:51Tim Spector:Feed your gut the right variety of plants, fiber, and other key nutrients, and it'll be able to do its job producing and processing hormones much more effectively. at Zoe we want to help you to listen to and understand your internal hormonal orchestra find out more about hormonal health with our free guide you can download it now at zoe.com forward slash fertility or click the link in the show notes back to the podcast 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.

16:45So babies like sucking things. So if you put your finger in a baby's mouth, they're going to 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 going to be getting. 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. was led by Nicholas Segata's team in Trento, 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, everyone's spitting in micro doses all around.

17:42Babies 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. So, Tim, is that a bit the equivalent of how I get a cold? I'm thinking back to what we learned in COVID, that 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? Yes. Even as we're speaking here, there's probably a sort of cloud in the middle here of these little microbes that we're exchanging, whereas we're much less likely to be exchanging our gut microbes, Jonathan, you'd be pleased to know.

18:18Well, 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 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 the mother. It's the same with everyone in their family. 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.

18:58Is that right? 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 we 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, 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 got to be swapped to like an equivalent place.

19:38So 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 light the oxygen. Is that right, Tim? Yes. So it's very different talking about in your mouth, on your skin, in your gut. They're all important though. So we mustn't just focus just on the gut. Skin microbes are incredibly important for preventing skin diseases and keeping us healthy. And oral microbiome is really important for fighting tooth decay and preventing heart disease, et cetera.

20:19So all these things are important, but we have to think of them slightly differently. 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 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.

20:56And in my experience, they're a bit quieter, more reserved. Like the more the people around you, like gesticulating and talking wildly, the more oral microbiome sharing that's going on. Is this what the science says? But in Finland, you 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 going to be sharing your microbes. 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.

21:33And 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. 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 going to react and give you peanut allergy or asthma or eczema.

22:16So how am I picking up my gut microbes from the world around me as I'm going from one years old to today? We don't know precisely, but there have 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 it might just be by touching a surface putting your hand in your mouth drinking a coffee generally between people you usually need more intimate contact so that's why we find that couples living together are going to be much closer in their gut microbes than say siblings living apart 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?

23:20Yes, 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 and so that's that's how we know that these effects are really real so if you want to show your gut microbes you cohabit with someone ideally you know you're in a close or sexual relationship but it's it's the physical closeness that's important And as soon as that starts to move away, you lose it.

24:02And that closeness is more important than genetics. So a couple living together are going to share more strains than identical twins, unless those identical twins are sharing a bed, which is unlikely. So there's like a big sharing of microbes if you have a sexual partner. Yes, exactly. And is there still a big sharing, like if you're in a household? And I guess I'm also thinking about kids. Is that also going on? 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.

24:38And then as those relationships get more distant, then it starts to fade apart. 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. 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.

25:17There'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? Absolutely, yes. Most of these studies are in animals, in 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. 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.

26:04So that was the first sign this was happening. 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, 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 you know if in your family you're surrounded by all these anxious folk and you're swapping gut microbes there is the potential that some of those microbes could be working in an unhelpful way on your own mental health but the opposite could also be true so if you're if with someone who's really happy and really relaxed hopefully you want to be getting their microbes as well.

27:02And it's still a bit unclear about which microbes work better. And I think it's going to be very personalized to say, are you more likely to be a recipient of them or are you more likely to be a donor of them? That we don't know in humans yet. But we do now know for the first time sort of what the good bugs and the bad bugs are. Is that right, 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 and how it affects the brain.