Gut Expert: Eating these 3 foods could improve your mental health | Tim Spector: Full Interview

0:00 My name is Tim Spector. I'm an MD. I'm  a professor of epidemiology at King's College in London and I'm also co-founder  of the nutrition and gut health company, ZOE. Today on Big Think, I'm going to talk  about the connection between what's going on in your gut and your gut microbes and how that  affects your brain and your mental health. I'll also be giving you tips about how you can improve  your gut health to improve your overall health.

0:35 Chapter one, how the gut microbiome works. The gut microbiome I like to think of as as  it's like a virtual organ in our bodies that we've only recently discovered. Something like  discovering we had a liver. And essentially, it's made up of trillions of little tiny microbes  that you need a microscope to see. bacteria, fungi, parasites, viruses, and other things we  still don't exactly know about. This collection forms a community mainly inside the lower part of  our colon, the large intestine. They essentially need to be thought of as mini pharmacies. They  convert the food that we eat into chemicals, into hundreds and thousands of different  chemicals. And those chemicals have this amazing impact on our body that we're only just  beginning to realize. This collection of microbes has something like 200 times more genes than we  have in our own human cells. That means they're much more versatile. They're more flexible in  what they can produce in terms of chemicals and they're actually more numerous than our uh human  cells. This is important because we evolved from these bacteria and the very first mammals and  then humans were built because they contained these colonies of microbes that could interact  with them and without these microbes we really wouldn't function and particularly our brains  don't develop normally. So, one way to think about our gut microbiome is either as a the  environment of a jungle or an amazing natural zoo where you've got these thousands of different  species of microbes that have taken over a little niche inside our gut that is very specialized to  them. They're not all fighting for the same food.

2:36 They've evolved just like animals have to get have  very specific tastes. The example I like comes from our own research where we found there is one  bug that only really eats or drinks coffee. It is so fussy it hangs around maybe for years just  waiting for that first cup of coffee before it will replicate and really start to be noticeable.  If we start thinking of coffee as a great example, then you think about all the other bugs that we  might have lying dormant in our guts that are waiting for us to eat something unusual, say a bit  of baobob or some beetroot or um some particular type of of nut or herb or spice. And so that's  a really important concept because we now know that the more diverse your gut microbes are, the  healthier you are. So that's why uh we need to be thinking how can I best feed these very different  gut microbes. Some of which might like coffee, others will only like uh the leaf of a bit of  cabbage, others uh might like seeds or nuts and others will like the leftovers from what the  other microbes have eaten. And this is also a really interesting concept because they they're  working together. They make sure there's no waste.

4:01 they are these perfect ecological beings. So  that the concept of waste doesn't really exist. And what they've shown in some mouse studies is  that um if you uh have a really strong colony of gut microbes that are very diverse, then you eat  your standard diet, you have no waste left over. But if you only have a few microbes, rather poor  uh colony, they're not very well diversified, you get leftovers. And when you get the leftovers,  then you get what we call the bad bugs will eat those uh because they've got something to eat.  So a really good healthy colony of microbes, like a zoo, is one where all the animals have a  role, they've got something to eat. Uh there's no real waste, and everything is used up. It's really  a marvelous model that we all love, a sustainable gut society. Although we all have thousands  of species of these trillions of bugs inside our guts, we're actually really different one to  another. And this is because as as kids uh when we're born, we're born sterile. So, it's slightly  random which microbes end up colonizing our own uh colons. And it turns out that the average  person only shares about 20% of their gut microbes with another. And even in identical twins,  they don't share many more than that. So it's a process that's part random uh part uh designed  that way and not very genetic. This means that we all have a different set of microbes producing  slightly different functions. Until recently, we didn't really know how good bugs and bad  bugs were interacting. And it turns out they're fighting for resources. The good bugs, these are  ones that eat your, for example, plants and change those plants into healthy chemicals that your body  can then use. And that has a a health effect. If they do well, they leave no food left over for the  bad bugs, by which we mean bugs that increase when you have a bad, you know, an average American diet  with fast foods and burgers, etc., lots of fat, those ones will increase and cause bad outcomes.  So, it turns out that if you're only having a a a good diverse diet, there's very little waste  to supply the bad bugs. This concept has changed quite recently because we used to be thinking okay  how do we get rid of the bad bugs that are causing inflammation irritation in there but now we know  it's focusing on on the good it's increasing uh those guys as much as possible essentially giving  them a greater diversity of food so that everybody gets something to eat and we can really use the  full armory of all those good microbes to produce the biggest possible possible array of chemicals  that the body can then use in the best way.

7:17 Chapter two, an unhealthy gut leads to an  unhealthy brain. When I started this research, we thought that the gut microbiome was really just  involved in things like obesity and metabolism. And it's only recently we've realized that  it does so much more. I like to think of it really interacting in sort of three key parts  of the body. Yes, it does influence metabolism, energy levels. It uh sends signals to the brain  about appetite and body weight and distribution etc. and is probably important in things like type  2 diabetes. But one of its key roles is acting on the immune system. Our immune system is pretty  crucial for virtually every common disease that we're encountering at the moment. From autoimmune  diseases, food allergies to things like preventing cancer by these our immune cells killing off  early cancers and the aging process itself.

8:18 So the immune system is a huge part of what the  gut microbiome does. And without a really good microbiome, you can't have a good immune system.  The third key thing that the microbiome does is interact with our nervous system. And it does  this through a huge network of nerves that are sometimes called our second brain. They're as big  as a cat's brain. And they probably evolved around our intestine before even our brain was formed as  when we were in the womb. And this network of of nerves connects to the brain primarily through the  vagus nerve. This is like a fast internet cable that picks up what's going on in our gut microbes  through the gut lining picking up signals in every single layer of the gut. So right through to  the the tiny connections right on the inside of the mucosa through every layer. So they are  actively sensing everything that's going on there.

9:20 All these neurons interconnect. They're picking  up signals from the gut microbes that are sending chemicals such as short- chain fatty acids which  they make when they break down fiber. They might be getting them directly from the microbes or from  the the cell wall of the microbes. They might be getting it from uh some hormones that the microbes  are making. these endocrine hormone sensing uh cells in the gut lining like GLP1 that's uh people  now know is how ampic works. They're picking up uh you know hostile chemicals, good chemicals.  Everything is is going through to these little little tiny neuron endings and they're being fed  into this vagus nerve through this incredible cable to our brain where it tells the brain what's  going on. This discovery has really changed our whole idea of the the gut brain axis because we  used to think the brain was telling the gut what to do. Turns out most of the traffic is from the  gut to the brain. People conceptually thought the brain uh was separate to the body. And this is  the carteesian view really that has penetrated and been very persistent in medicine for centuries  and still means the reason that psychiatrists and uh medical doctors don't really mix and that we  have separate hospitals and separate training.

10:52 And yet now the latest science is showing  that there really is very little difference. The brain is just another organ. It is not the  brain controlling the rest of the body. It is just another organ and it relies on the gut for  most of its information. Many people have vaguely heard about inflammation. I was unusual because as  a kid uh I heard about it a lot because my father was a professor who focused on inflammation.  Before it was trendy and well it was trendy briefly then it went out of fashion. Now it's  definitely back and everyone needs to know what it means. It's a normal response we all have to a  threat in in our bodies whether it's uh stress or it's an infection or something alien to us. Our  body responds. It sends all these white cells from our body to that site and triggers a whole  careful reaction that gets rid of that threat as quickly as it can and goes back to normal. Now, we  currently have uh problem of what's called chronic inflammation, which means it lasts too long.  So instead of getting a brief brief spike of uh inflammation in response to a threat say some  bad food uh that returns to normal our bodies uh have become in some way uh changed so that that  threat level stays up. So we are suddenly going through life at a a a threat level that isn't our  baseline. That may be due to our environment of terrible food. Uh it could be due to pollution,  pesticides, all kinds of things. But or it could be due to our stressful lives and social media.  Whatever the cause, it's true that in the west we have stress levels based on the levels of  inflammation or our immune system that are higher than you would find in Africa or India or uh where  our ancestors came from. I also learned a lot of it because I was a rheatologist originally in my  one of my early careers before I I changed several times and saw patients with rheumatoid arthritis  um autoimmune disease who suffered a lot and they were constantly tired because of the inflammation  in their joints which spread to their bloods.

13:26 I didn't think much about it because we thought  they were tired and depressed because their joints hurt. And that's really what we were told. Oh,  it's normal. They are uh tired and depressed. They've got quite bad crippling arthritis. But it  turns out it was just the reaction in the brain to what was going on in the rest of the body.  We now know that many mental health problems, virtually all of them have been studied so far,  have above average levels of inflammation and they also have abnormal gut microbes. So there's a link  between uh mental health disorders which nearly all of them have reduced energy and reduced mood  to some extent. even in forms like psychosis and schizophrenia or even in uh ones you don't regard  as mental health but brain problems like epilepsy or migraine. This is also true. So there's a  general increase in inflammation in the blood.

14:35 There's also a general uh abnormality of the gut  microbes compared to uh people who don't have any mental health problems. So we're seeing this  picture developing whereby we are getting uh much more common ground to explain this explosion in  mental health problems. That's that's based not on the old theory of uh a deficiency in certain brain  chemicals or an excess of brain chemicals but due to this underlying inflammation which probably  starts in the gut and then sends those signals to the brain. So an obvious question is where does  this inflammation come from? What's triggering the body to in a way overreact and keep overreacting  to stimuli rather than dealing with the problem, getting rid of it, going back to the base  state which is what we know that our healthy ancestors had. Inflammation is both a cause and  a consequence of many things we're talking about.

15:44 The most obvious cause in the west of this  uh pandemic of mental health problems is the fact that since the 1970s, we've been eating uh an  increasingly bad diet. The standard American diet, the SAD diet, which is denuded of fiber,  it's plenty of saturated fats and it's full of ultrarocessed food. All of which have been  shown in uh particularly mouse models to cause inflammation in the gut of those mice leads to  many more bad bugs compared to good bugs. There's not much for the good bugs to eat. The bad bugs  take over. They like an inflammatory environment and they actually produce chemicals that will  stir up uh the gut lining and that environment to in a way be more toxic and raise the levels  of the immune cells in the body that think in a way they're infected or diseased in some way. So I  think that's the unifying idea of how uh bad food on a long-term basis causes this increase in the  imu the immune cells which you've got to remember that the gut microbes probably by evolution are  there to pick up signals from the environment tell the brain who that can't really see outside the  little skull what's going on. Gives it an idea of what's going on. It's this consciousness and it's  picking up these signals and if those signals are bad food, inflammation, heightened you, fear, it's  like, gosh, there's something bad going on here.

17:27 Let's signal that back to the brain. What does the  brain do? It goes into some sort of lockdown mode, a sickness behavior, some people call it, which is  quite natural. It it's getting a signal from its main communicator, the gut, along the vagus nerve.  It tells it all kinds of [ __ ] is happening down here. This is not good. We're getting really bad  signals. How do we react in evolution? We'd say it's like an infection. We lower our mood. We  lower our sociability. We lower activity. We tell the body we're tired, so we rest. And  that's what you get fatigue, mood change, and all the other associated factors, and you end  up with what we're calling depression. That's my way of thinking about this problem for perhaps the  commonest factor that's changed in our lives in the last 50 years. And particularly why in kids,  we're seeing this this pandemic at the moment.

18:24 kids that have had mothers that were had terrible  diets that passed that on to the kids and then basically they've had ultrarocessed foods for the  the whole of their lives uh without ever having any real food to nourish any the few good microbes  there are. Only the bad ones have been surviving in that jungle uh just on the fats and the scraps  and the artificial sweeteners and the chemicals etc. So I think that for me is the the key model.  You can also uh think of other ways that you might get inflammation and my research in this area is  not that I've done it myself but looking at the the literature is that many of the risk factors  for mental health disorders are all the same. So it doesn't matter which of these so-called 300  different disorders you have the risk factors are the same. childhood stress, trauma, poor diets  and um living in urban environments. All of these things increase stress and they now know that that  stress you can see as an increase in inflammation in the in the immune system. So just psychological  stress can also cause this as well as uh in a way dietary or gut stress end up with the same common  pathway. After a bad night's sleep or some stress, your body seems to crave fatty and sugary things  that are unhealthy. And we've all experienced that after a a poor night's sleep or a hangover or  whatever it is. You reach for the the one thing that you think you you need, but it turns out  you're wrong. Your brain's given you the wrong directions, and this is going to make you probably  feel worse. So this sort of explains this loop people get in particularly uh with depression  or anxiety. The brain is telling them to do one thing that actually is making it worse. And so  it really explains why people with low mood and depression end up eating badly and can't get out  of it and it's making them worse. hadn't really thought about the gut brain connection quite  as much. But about nine years ago, my mother uh suffered a stroke. She ended up uh in a care  home with uh dementia. Each time I visit her, you know, I am reminded of the fact that so many of us  now are potentially facing this fate in old age.

21:02 And it's not something that anyone really wants.  dementia is probably the the worst way to go. So, it's made me think about this more and start to  look how my own research could potentially have an impact or help not only myself but other  people prevent dementia or at least delay it uh considerably. It turned out my mother with her  stroke and subsequent acceleration of dementia probably had what's called vascular dementia  which is a fairly general term that affects about one in three people who get dementia.  It's the second commonest form and it tends to occur in phases so that the blood supply to  the brain is getting progressively diminished and knocked off probably by atherosclerosis in the  arteries uh supplying the brain. The other type of uh dementia that many people hear about is  Alzheimer's which is probably the commonest form of dementia perhaps affecting uh 60% of  all cases and it can start in a similar way with uh loss of memory or cognitive function and then  progresses uh at a m usually a more sustained pace um that doesn't have these separate phases. is  and that's caused slightly differently it being distinguished by having these protein folds  in the brain these amaloid and these towel proteins that have led to some of the damage  in the brain as the brain has been shrinking now we don't know they are causal it could be  that these proteins just are part of the damage after it's occurred but we believe that there are  some common causes of both these types of dementia that the risk factors seem to be quite similar  in both cases. We can link this back to gut poor gut health. the picture of gut health that uh  where you have a low ratio of good to bad bugs, you've got poor diversity of species and you got  an inflammatory component going on there is a major risk for both types of dementia as is things  like type 2 diabetes which probably is involves the energy supply to the brain which affects both.  So for practical purposes, you should be trying to prevent both kinds of uh dementia because they  have a big overlap in the causes although they can look very different at the end. So we have gut  microbes all through our intestinal tract and that re means from our mouth to our anus and some bits  are harder to access than others. It's very hard to know what's going on in the middle bit, the  small intestine, because it's very hard to reach.

24:09 And so we rely generally on what's happening in  stool samples, but we also can look at what's happening in our mouths and our saliva where which  is teeming with microbes that are there basically to protect us, but also start the first bit of  digestion of food. And just like in our colon, there's a little colony of microbes there that  uh interact with each other and you have good ones and you have bad ones. And if you provide an  environment that uh doesn't clear away your food, leaves food waste, the bad bugs will accumulate  and they can lead to inflammation. And this tends to happen um at the interface between your teeth  and your gums. And we know that gum disease is very prevalent in in the west. Perodontitis and  specific bugs absolutely love the environment there. You get slight redness and swelling which  is a sign of inflammation and you can generally see it there. Your gums might be slightly tender,  might be swollen, might be red. And in certain cases, they will bleed if you uh floss them or  brush them hard. That's a sign that you've got inflammation there that they're bad bugs living  there, eating the bits of food. They form plarkes.

25:32 And a plaque is a a complicated structure that's  made by these microbes that builds up like a protective shield. So that in a way they can keep  uh digging away, eating things uh and they're protected from you uh brushing them away. So our  teeth, it turns out, are a really good place to look for inflammation. And remarkably, we we we  learned about 10 or even 15 years ago that dental decay was related to heart disease. And there  were certain microbes they found very early on. I think it was strep mutans is associated with  uh increased risk of heart attacks. This was very strange when that first came out. I remember now  we were able to look much more broadly at all the microbes. We know that poor uh mouth uh hygiene  means high rates of bad microbes compared to good ones. These are pro-inflammatory. And if you're  not brushing and flossing your teeth, you have roughly a 25% increase in heart disease. And some  studies are showing anything between 20 and 50% uh increase in uh dementia and cognitive decline.  So suddenly we've got a really good example of how um uncontrolled inflammation in our bodies  can have a direct effect on areas we hadn't really thought linked at all like our brain.  I think this gives people the idea uh of how important it is and how preventive action can work  because if you then brush your teeth regularly, you'll reduce that risk perhaps by half. So rather  than 50%, you're down to 25%. But if you then floss um which is gives you an extra say 30 or 40%  of cleaning you do that really well and you can get rid of the plaque and get rid of the bleeding  and the the inflammation you can get right back to zero. So I think this is a marvelous example of  how we need to battle inflammation in our bodies really to save our brain health. Well it's hard  for the average person to know what their gut health is like. Basically, it means that your uh  your trips to the toilet are regular. You look at your stool and you see, is it fairly soft? You  don't want to be a cowpat. You don't want to be a sheep dropping. You want something in between  and you are going once or twice a day. If that's the case and you're not getting any bloating and  you're not having constipation or diarrhea or, you know, a lack of regularity, then you're  probably pretty healthy. If the opposite is true and you're having any of these problems,  your stools look rather strange, they're, you know, they're varying, you're only going once  or twice a week, then it's highly likely you have uh gut problems and uh you need some dietary  help. We talked earlier about thinking about your mood and energy. Are you fatigued? Is your mood  lower than it should be? Are you getting uh some bloating? These are signs you do have gut health  issues and you should address them. Improving your plant intake will improve your fiber. You  know, do a bit of exercise, have some more water, etc. Having done that, if you want to test your  gut microbiome, which I think will be standard of care in five years time, it's very difficult  at now to know who to go to. Your general family physician may or may not be able to help. A  functional uh medicine doctor probably will, and we're seeing more of those more holistic type  of uh doctors appearing, but uh it's not something that's very easy to do. But I think a good gut  microbiome test is much more useful to you than getting your your genes tested or your DNA.  It's really your metabolic blood pressure. Um, if your gut health is good, most of the rest of  you is going to be pretty good. And if it's bad, you're going to have problems. Chapter 3. Eight  tips for maintaining a healthy gut ecosystem.

29:51 The old way of thinking about nutrition is the way  I was taught and doctors are still being taught is that essentially there's only four things you  need to know about nutrition. It's calories, how much fat there is, how much protein there is,  and how much sugar there is. If you get those four things right, everything else will follow. We've  been following that advice for the last 40 years and it's been a complete disaster. It doesn't  make sense scientifically anymore. Uh it's only really helped the food companies uh sell us  more crappy products and it's led to a disaster uh of unbelievable scale for the public health.  Real food, unlike fake food that is made just from a few ingredients, contains thousands of  chemicals. And all of these uh play a role in our body because they then nourish the trillions  of microbes inside our gut to produce thousands of other chemicals that our body can't produce. It's  only by focusing nutritional health guidelines on this new organ in our body, our gut microbes,  that it all makes sense. We have to have a seismic shift in our idea about nutrition in order to  make healthy progress and focus on gut health and what are the key principles to improve all of  our gut microbes which will help us. As I've been studying the gut microbiome, I've been obviously  thinking of how I can translate that science into progress and practical tips for people in  various ages and states of how they can improve their gut health. The first one is what we call  mindfulness. And this seems a bit strange. What what's he talking about mindfulness for? Well,  I remember when I uh started to change my diet, I decided to be vegan. It was an easy way to  change your diet. as a a temporary fix if you like because it meant that when I was going to medical  conferences I would stop and think before I just took something from that tray from that buffet I  would say what's in it uh was there meat in it or is there dairy in it and we don't need to be that  extreme all you need to do is to think about what you're eating just for a second before you grab it  or you put it in your mouth So mindfulness in this context means just stop and think am I hungry do I  need this what's in it you know and what what are those contents are they going to uh have an effect  on me and then what effect is that going to have on me if I do eat them. So these sort of three  steps that I think are important in mindfulness is an important realization that food is much more  than just calories. uh is it going to affect my mood? How am I going to feel in three hours time?  Uh what what are the long-term consequences? But also, is it going to be really tasty? Am I going  to really enjoy it or am I just being forced by marketing by big food to eat this rubbish that  I don't really want? So there three uh steps in this this concept of mindfulness. We just want  people to stop and think. That's number one.

33:18 So the second principle, probably the most  important that we've found scientifically is to eat a diversity of plants. It's not about eating  the same plant many times a week. We think that the science is pointing us to is something around  30 different plants a week gives you optimum gut health. This is a study that I took part in with  the British gut and the American gut about 10 years ago where we saw that the sweet spot for  gut health was people eating around 30 different plants a week. It looks like it might be slightly  more than that, but certainly 30 is a really good target. It turns out it doesn't matter if  you're vegan or vegetarian or an omnivore.

34:04 It's the people that eat the most plants have  the healthiest gut, which I think is is really interesting. 30 plants to many people say that  sounds way too much. The average American probably has between 10 and 12 plants a week. How do I get,  you know, how do I get over double that? Well, you got to remember what a plant is. It's a it's  not only a fruit and a vegetable, but it's also a nut. It's every different type of seed. It's an  herb. It's a spice. It's even things like coffee, which is a fermented bean. So when you just  change your mind a bit about what plants are, then it becomes easier and fun to add them to  your plate. Think about more rather than less.

34:50 Most diets are all about excluding things. And  what we're trying to do for our gut health is to in include more things. We've got little microbes  just waiting around for that bit of baobob or that particular nut or seed or berry. uh the chemical  that comes from it. So the more you can give your gut microbes, the better. My third guideline is  to eat three fermented foods daily. So I've spent the last three years researching fermented  foods and have a book on that subject. And what was really interesting is I I didn't think  it was a topic worth discussing three years ago because the science wasn't really up to it. But  I've been convinced by a couple of studies. The first was from my colleague Christopher Gardner  at Stamford, a very detailed but small study of adults who were told to eat five fermentss a  day, comparing that group to a high-fiber group.

35:53 And what they showed was that not only did the gut  health improve in the fermented group particularly the immune system was impacted and they had around  25% less inflammation. So suddenly moving from anecdote and lots of small not very good studies  in the literature uh that were all pointing the same way that fermented foods were good for you to  suddenly a mechanism that this can really impact your immune health in different ways to just  rather than just eating lots of fiber and plants.

36:25 People think what is a ferment? A fermented food  is something that's been transformed by microbes into something better. So you transform milk  into cheese much more interesting than milk. You transform grapes into wine. Uh you're transforming  cabbage into sauerkraut. So think the 4Ks. Keir, uh kimchi, kraut, kombucha. Kombucha is uh  fermented tea, which is all really good for you. Most cheeses, if they're not, uh made artificially  in in in factories, are good. Yogurt is great.

37:02 All the soy products that you see in [ __ ] Japan,  miso paste, all these krauts and pickles that are fermented in salt are really good for you. So  variety is important. They've all got plenty of different microbial species and they're probably  better for you than just taking probiotics from the pharmacy or the drugstore. So my  recommendation is to build up to three fermentss a day as an extra boost for your immune system and  your gut microbes. a big fan of fermented foods now because the science has finally caught up.  The fourth guideline is to diversify your protein.

37:40 We're going through a protein craze at the moment  where every product has added protein in it. Every uh American thinks they're deficient in protein.  And um there's nothing wrong with protein. It's not particularly harmful. But if you don't uh  need it, you lose it. You can't store it. So you pee it out or it gets converted to fat. If  you are trying to get more protein and perhaps 10% of people are lacking in protein because  they're unwell, they might be elderly. They're uh trying to uh build body mass or try and  not lose it too much as they're on the these um weight loss drugs. Then my view is you should  be trying to think about other protein sources rather than just uh red meat. The one that comes  to mind are beans and lentils uh things that have really high protein content but also contain  lots of fiber. This means your microbes can actually use that at the same time as your body's  getting that protein. So that's a real reason why we should be switching eating many more beans and  pulses than we are currently. They're very cheap, they're accessible, they're good for the planet,  and our microbes love them. Guideline number five is focus on quality, not calories. For decades,  we've been obsessed with the calorie as the main source of describing food and nutrition about  whether it's healthy or not. There are hardly any uh nutrition scientists who now believe in the  dominance of the calorie. It's only a tool for the food companies to make rubbish food uh seem more  healthy because it is lower in this magic term.

39:35 The science tells us that these uh in the vast  majority of people fail. It's really impossible for most people to follow a calorierestricted  diet for more than a few weeks. And even if they do lose weight, as most people do, uh virtually  everybody regains it because your body's appetite signal is turned up. The brain has finally tuned  to know if you're uh not getting enough energy and it switches up its thermostat to ramp up your  hunger signals. Your body is designed by evolution to overcome that pure uh calorie signal. The other  problem with calories, not only the fact that it's it's virtually impossible to calorie count and  and lose weight, is that it disguises the food in ways that gets us to stop thinking about the  quality of what we're eating. And that's what the food companies have been doing for the last  uh 40 or 50 years, trying to switch our thought away from the fact that they are just making this  uh crap food out of a few ingredients that have government surpluses, away from the food we should  be eating, which are whole foods, which is what our gut microbes want to eat. They want to eat a  variety of foods that are in their original state that have the the casing uh that contains most of  the fiber. They want the skin on it. This is where most of the nutrients and ingredients are that  uh we need for our bodies to work really well.

41:13 This is a really important step as people um try  to disregard the calorie which effectively doesn't have a major role in our any of our plans and we  ignore the calorie completely. So tell people it doesn't matter. It's all about the quality of the  food, how it's going to impact your gut microbes. And once you do that, it's very liberating for  people to think I don't have to worry about this. And generally, if something's got low calorie  on it, it's a poor quality food. You should be avoiding it. Number six, avoid high-risk  processed foods or high-risisk ultrarocessed foods. These are the foods that make up 50 to 70%  of the American diet hire in kids. And most those foods are really harmful for us. There isn't a  universal definition of an ultrarocessed food.

42:09 We think that ultrarocessed food itself is  is too broad a term because it most people use as anything that has got an additive in it.  Some of those additives can be like vitamin C, therefore not particularly bad for you, whereas  others are are dreadful. And the worst ones, the ones we categorized that make up 25% of uh  the American diet have a number of components that make them particularly harmful. Remember,  these are foods that are mainly made from cheap ingredients that are government subsidized like uh  like maze uh like uh soy and uh wheat and sugar.

42:52 These are things that are plentiful and taxpayers  are paying for them to be cheap and they have surplus of it. So they've got to make create foods  with them and they do that really effectively. and they try and upsell them by adding additives  to them that change their color and they change their texture and they change their taste.  And some of these additives are not too bad. Others are quite unhealthy and others are really  unhealthy for us. Some of them are associated with cancer. Some of associated with mental health  problems in kids. You have emulsifiers which glue them together which are bad for our gut microbes.  You've got artificial sweeteners which uh many of them develop from the petrochemical industry which  our bodies are not used to that cause our microbes to produce funny strange chemicals in response  and are generally harmful. You've got others that we still don't know how bad they are. That  that's the additives. Then you've got uh the hyper palatability that the companies use a mixture of  salt, sugar, and fat in those combinations to make that food override your normal fullness signal.  So they do this very deliberately. We all know we've eaten a big bag of chips or whatever it  is in front of the TV and it's it's got potato, which is starch in it. It's got um salt. It's got  usually um some some uh fats in there and it's that sugar, salt, fat in the perfect combination  that these brilliant food scientists have created that will tickle our brains into uh thinking we  can keep eating them and we just don't get full.

44:44 So hyper palatability is a component of 70% of  these foods. The other component that you need to be looking out for is is it something that you can  eat super quickly. Uh its structure has been taken away. So you strip off all those bits of plants  that make it necessary to chew it and you've just got the inside uh bits. So we end up eating baby  food. They melt in your mouth, dissolve away. You can keep eating them without even noticing it,  without exercising your jaw. And then finally, the best from the food company's point of view  are foods that you can get lots of energy in really quickly without noticing it. And this is  called calorie density. The worst offending foods have those. So these are the the four categories.  The ones to look out for are the ones that have all of those components. And that makes up 25% of  the American diet. breakfast cereals uh for kids, uh most children's yogurts, um most savory  snacks, most cookies, uh most ready meals, most u sodas and drinks, even if they are low calorie.  So, not only is it bad for your gut microbes, it's also going to make you uh keep eating and become  obese and have all those problems of diabetes, etc. I don't think it's realistic to cut them all  out completely. And my view is that yeah, you can still have the odd uh treat, but don't have any  of these as a regular part of your diet. Number seven, try and eat the rainbow. You may have heard  that before, certainly been around a while, but we now know why it's good to eat the rainbow. Rainbow  plants and uh especially fruits and vegetables have rich colors. And that's what we're looking  for when we trying to select something to put on your plate is to try and get as bright and as  varied as possible because plants that have these bright colors tend to also have high levels of a  defense chemical called polyphenols. Plants like humans, you know, have a defense mechanism and  this is their defense mechanism. They are fighting off insects and sunlight and d dr dr dr dr dr dr  dr dr dr dr dr dr dr dr dr dr dr dr dr dr drought etc with these chemicals that turn out to be  actually very good for us. They used to be called antioxidants which is a rather vague scientific  term. We now know that our microbes can use these polyphenols as a form of fuel. If they're getting  this, it's like they're getting extra gasoline.

47:23 And so this engages all our microbes to be  healthier. So as well as breaking down the fiber in the these plants, they're also getting these  extra chemicals which is acting as a fuel which makes them even more productive. So nature's given  us these clothes, bright colors. For example, you got a store uh you got an iceberg lettuce  there and you've got a rosolo, an Italian one with lots of purple uh leaves on it. always go  for the brightly colored one that will have a thousand times more uh polyphenols than the uh  ubiquitous iceberg lettuce whose only advantage is that it stays forever in your fridge. It has  no nutritional value other than that it will come still be there after your vacation. The other  clue in nature is they can be bitter as well.

48:16 So, slightly bitter tasting plants like your  broccololis, the cruciferous vegetables. Uh, nuts and seeds. You've got uh extra virgin olive  oil, which is my oil of choice, is really high in polyphenols. The best ones will make you slightly  cough, and you want them to be really nice and young. You've got dark chocolate. over 70% is  generally healthy because that cacao bean has really been um fermented and is uh really strong  in polyphenols as is coffee. If you like a drink uh the the the only one I'd recommend for your  gut health is probably red wine which has high levels of polyphenols uh again in moderation.  So they're the tips that nature's given us uh to identify why eating the rainbow and bitter  foods are actually good for us. The final tip is try and give your gut a rest. And by that I mean  timerestricted eating. 20 years ago and certainly when I was at medical school was the idea that we  should be uh grazing not feasting. Things have now changed and we now realize that constant grazing  is what your gut microbiome doesn't like at all.

49:36 We know how important sleep is for our health.  Uh getting eight hours a night can really extend your lifespan, improve your immune system. Well,  the same is true for our gut microbes. They have a circadian rhythm. They actually go to sleep  and they need this time to repair the gut. So if it's eating all the time and you're having late  night snacks, early breakfast, they're not getting the natural time they need that our ancestors  had for millions of years to clean up our gut, particularly the lining of the gut where the  mucosa is. This is really important as an immune barrier and the healthier that is, the healthier  generally our immune responses are. So give your gut 12 to 14 hours to recover overnight and this  is the basis of timerestricted eating. The way timerestricted eating seems to work is through a  number of mechanisms. The first is by leaving that gap uh in time your microbes are not focusing on  eating and you have a a defense team that comes out at night. A bit like in American football you  have a different teams for offense and defense.

50:47 defense comes out. It cleans up the lining of  your mucosa. That tidies up the gut lining, makes it more efficient, helps the immune system.  You're also getting metabolic advantages so that uh your gut health is generally better the next  day because it's all been tidied up for you. There isn't that much debris lying around and you get  less unhealthy bugs over time. It also seems to be uh better for your mental health. A lot of this is  uh anecdotal, but we did do a large study in ZOE of 140,000 people asked them to do timerestricted  eating. A third of people hated it. They were snackers and they just found it really difficult.  A third loved it. They're still doing it years later. And what we we learned was the people  that that were adhering to it had improved mood, energy, and less hunger from doing it. So there  do seem to be other benefits that we still uh are looking at. And it also helps  you avoid snacking and we know that uh mindless snacking accounts about 25% of  calories in in in the United States and the UK. So it just makes you a bit more thoughtful  about what you're eating if you're trying to give your gut microbes a rest. Timerestricted  eating is a form of intermittent fasting, but you're not restricting calories. you're just  eating the same food you would normally eat, but in a more limited time frame. So, for people  wanting to give it a go, I would say the easiest thing is to start with a little rule like leave  at least 2 hours before going to bed where you're not eating anything else except maybe some black  tea or or or water. That way, your gut will have a chance to recover and hopefully you'll notice the  difference the next morning. And if that works, then you can extend it and maybe say, "Okay,  I can try this uh for a 12-hour overnight fast as well." We are moving to the idea that many  people can do very well just having two main meals a day or maybe combining breakfast and  lunch. The concept of brunch many people are enjoying around the world and see actually I  feel quite good at the weekend when I do that.

53:00 I don't necessarily need to eat first thing  in the morning. And I think we're realizing that this this idea of three big meals and maybe  three snacks events has been forced on us by the food industry. Mr. Kellogg was probably the first  one to say that everyone had to have a breakfast before doing anything otherwise you'd be unable  to work. It's Kelloggs for breakfast [music] and a happy happy day. I personally find, you know,  I'm doing this interview now and I decide not to have breakfast because I'm actually sharper uh  when I haven't eaten just before it. So, for me, uh two or three meals, no major snacking events,  eating relatively late. I eat until [snorts] say finish eating maybe 8:30 at night and then will  try and not have anything to eat before about 10:30 the next morning. That suits me. When we  asked the 140,000 ZOE members what they preferred, they found two-thirds preferred that same rhythm.  One-third uh couldn't miss breakfast. They said, "I really like my breakfast. I'm hungry when  I get up. I want to have my breakfast but then I'll finish eating around uh 6 6:30 and so people  have different rhythms as we discovered. I think there is a bit of personalization to this and you  have to find the one that suits you but my advice would be don't follow what the big food companies  want you to do. Uh do experiment find out what works for you and follow that. So there you go.  There are my eight guidelines. The key message is you got to eat for your gut microbes. If they're  happy, you're going to be happy. Chapter four. Why the internet gets dieting all wrong. I think  it's very hard at the moment for the average public who's not a scientist, not a doctor to know  what to do for their health. Reports, you know, one day that coffee is bad for you, another day  coffee is good for you. Uh eggs are good for you.

55:08 one day and eggs are bad for you. Public has to  realize that the media thrive on these stories on these scare stories. Uh they love food stories.  So you know our newspapers and social media are full of all this stuff. So the the key is to not  overreact and to realize that your core diet is the most essential and that if you are looking  after your gut microbes and you're doing most of those those eight things we discussed, it doesn't  really matter what else you do or don't do because the majority of your plate every day is going  to be full of good stuff. Whether you have eggs, whether you have coffee, whether it's good or bad  is not going to be crucial to your health. What is crucial is that majority of the time you're  doing the right thing. 80% rule is what I love is you 80% of the time you're doing uh things  right and you don't worry about the odd time the you may have the odd trip to McDonald's  once a month. If your gut health is good, it will cope with the rest. All good scientists  should change their minds when the data changes.

56:20 And I've made lots of mistakes in my career. Most  of it not my necessarily my fault. There was some data on margarine being healthier than butter. So  I changed our fridge back, this is 20 years ago, to having these low-fat spreads and kicked  out the butter. My wife objected. She's she's uh French speakaking so she wouldn't have any  of it. She kept the butter so we had separate compartments. And I realized that I I got it  wrong and now there's no low-fat artificial ultrarocessed spreads in my fridge. So I'm  constantly changing my view on many of these things. I'm much more open-minded than I think I  was before. So it's an exciting time uh to be a scientist. I think what is important to realize  is that science is moving on at a pace. It takes on average 20 years for doctors to change their  practice from the time that uh a new uh scientific discovery has been uh proven. So there's a big  lag between what the latest science is delivering and what the latest practice is or what your  insurance is going to pay for etc etc. the public is stuck in the middle here. And I think what's  important is to see when there's a consensus, when there have been a number of studies that are  all pointing in the same direction and they've got someone they trust that is telling them yes,  the summary of this data convincingly is saying you need to do this. I think the lesson here is  that the public needs to up their game a bit to be a bit more educated to know that I can create  any outcome I want in a test tube. You need to disregard that. I can do the same thing in mice.  That would probably be pretty irrelevant. Getting people to think, has this been tested in humans?  Was there a placebo arm? Is this really going to change the practice of most people without just  jumping on every bandwagon that people want you to to jump on? At the same time, realize that the  guidelines that are out there from government, etc. are very behind the times. and realize that  uh a lot of the stuff people might be seeing on social media is probably too far ahead of the time  just so someone can talk about a test tube study or a mouse study that sounds exciting or wacky or  uh accounts for some weird theory. There's lots of people on to looking at paleo diets or keto  diets, people who only eat meat or people who only have really high levels of fat above 70% that  claim miraculous benefits from it. Most of these diets work shortterm because if it's away from  ultrarocessed foods, then generally it's going to be healthy uh to that extent. And so people  who go on a carnivore diet, which is a an idea of what our ancestors ate, uh, a very selected  idea of what our ancestors ate, they will feel benefits for a few weeks, might lose usually lose  weight. Those people will then tell everyone about it. Isn't it amazing? People who go on very strict  gluten-free diets, keto diets, carnivore diets, seed oil free diets like the idea of excluding  things. So that suddenly you're belonging to this club of people that are excluders and that's  perhaps the attraction and that's why most religions have some food based ideas that keeps  that community together. So they they become a little group, they feel better for the first six  weeks and that's when the problems start. So, a they might be very hard to sustain like a  keto diet is really hard to sustain those high levels of fat. Most people feel rather sick. And  long-term your gut is suffering. Any restriction to the amount of plants that are going into your  gut will start to have an effect of killing off the good ones and making the uh overgrowth of the  bad ones that are just uh eating the scraps of what of what you're eating. And so long-term you  have immune problems uh and gut health problems, mental problems down the line. So I think uh  exclusion diets will work short term and people might want to do that as an experiment to see how  they feel, but then they've got to long-term start looking after their long-term gut health, which  is the thing that's going to keep them alive and keep them free of diseases. What I like about  our message is that it's not about exclusion.

60:53 It's about inclusion at the very best level. All  that mattered was you're getting that big variety. There's those those u 30 plus plants. I get a lot  of questions about uh organic food, for example. Should we only be eating organic food? How bad  are these pesticides and these herbicides for us? These are great questions that don't have  simple answers. It's always better, I think, to eat non-organic vegetables than not to eat them  at all. Yes, our fruits and vegetables are sprayed with pesticides and herbicides that are probably  slightly negative for our health, particularly if you're uh pregnant or you're a young child or  you're have some immune problems or you're sick.

61:45 For most of us, it's a low-level harm. You want to  avoid it, but it's not life and death. And that's the way I I see about these things. We should  also be try and supporting farming that's moving towards organic because we'd all prefer to live in  a world that didn't have these chemicals sprayed to kill every kill all kinds of life. And we do  know that these pesticides harm our gut microbes. So, they've been shown to be relatively safe for  our genes. They don't alter our genes, but they do interfere with the genes of our microbes.  So, in theory, I don't want to eat pesticides uh at all. The reality is it's tough. I don't like  paying twice as much for my food. At home, what I do is I uh yeah, I get organic food delivered  on a weight a basis, but when I'm out and about, I'm not that worried about it because it's better  to eat vegetables that have some uh chemicals on them, wash them off than not to eat them, and  deprive your your gut microbes of a meal. Now, some foods I would worry more about than others  because they're not all the same. Uh if you look at oats, oats have a terrible record because  they're sprayed multiple times before harvesting.

63:02 So they can have um many times the levels of other  crops. So I'd always go for organic oats and you can find those in stores now. It's worth paying a  little bit more for those. Similarly with berries, if you can get uh organic strawberries that aren't  sprayed, they'll be much healthier. But if you're talking about things like oranges or avocados,  I'm less worried because you don't not eating the skin and a lot of the pesticide is is in that  skin. So, it's a it's a slightly nuanced question, but personally, I'm not obsessed so that uh I  get stressed every time I go out to a store or a restaurant about not finding uh the exact product  I want. It's about not exposing yourself to things over long periods of time, not the occasional  uh event. That's really important. Another thing people ask me about is mercury content of large  fish. If I'm a fish fanatic and I'm I'm having fish two or three times a week, I wouldn't want  want to having the those same large fish because I would be building up high mercury levels.  You might want to have your fish checked. And there are places you can buy fish from that have  guaranteed low mercury levels, but I'd be going for smaller fish which are also more sustainable  for the oceans. My own personal choices of food are I'm thinking about uh the health consequences  of the food, some ethical considerations about it, uh but also the effect on the planet. Fish is  particularly pertinent to that because most of the fish we get is is uh grown in fish farms. um  some which are good, some of which are bad. So, it's good to be thoughtful, but in general, go for  small fish that are more likely to be sustainable and also have very high levels of the omega-3s  that are really good for your brain. I'm often going to people in restaurants and the they're  very worried about the salt content and they're asking uh for no salt to be added to their food.  This is a subject that I was interested in because I had high blood pressure diagnosed came on  suddenly about 15 years ago and I tried salt restricting for a couple of weeks and see if it  would change my blood pressure. I didn't notice the difference. So, I started researching this and  it it turns out that um for the the average normal uh 50-year-old, cutting out salt virtually  completely from your diet improves your blood pressure by about 1 to 2%. If you have a problem  with uh hypertension, blood pressure, it might increase to about 4%. And when I looked in detail,  it turns out that there's only about one in five people that are really sensitive to salt. Four  out of five of us are not that sensitive. So it has an exaggerated effect that most people aren't  aware of. So I tell people that if you're worried about salt, do a proper test. Take your blood  pressure three times a day for two weeks having no salt salt at all, which is horrible, and  see what effect it has on your blood pressure.

66:14 What I also found out is that eating just  something like beetroot can increase can reduce your blood pressure three times  more than salt restriction. Similarly, just changing your salt to a potassium salt can  have three times the effect of salt restriction. So most people don't have to worry nearly as much  as they are. And I think it destroys a lot of the pleasure of eating and stops them maybe enjoying  vegetables as much or fermented foods as much because they're worried about the salt content.  That's why it doesn't come into my guidelines. And if you're avoiding most of the ultrarocessed  food, you're going to be avoiding the salt.

66:49 There's really good data showing the salt you  add at your table is negligible effect on your health compared to all the rubbish you're getting  consuming too much ultrarocessed food. When I was researching fermentation, I looked at kimchi  eaters and then anyone who's had kimchi knows it's really tastes really salty and when you make  fermented foods, you have to add a lot of salt. They looked at um over 10,000 kimchi eaters in in  in South Korea, compared them to non-kimch eaters of the same age, and they actually had lower  blood pressure than uh the non-kimchas. So, the benefits of having fermented foods and plants,  and plants contain potassium, outweighs any effect of the salt. That's a great example of a nice  simple solution being exaggerated because of rather outdated research that stayed in the in our  in our minds. Yes, salt has a role. Most of it's an ultrarocessed food. Eating plants would have  a much better effect on your blood pressure than worrying too much about salt. A lot of people also  think that diet isn't that important if you've got a rich supply of supplements and there's a lot  of marketing directed at people like that to say you don't have to worry about your diet. You just  got this green powder you take every morning with 80 different uh chemicals and vitamins. That's all  you ever need. Again, that falls into this idea of reductionism. a nice simple solution to a complex  problem that usually by definition is wrong. And all the studies suggest that eating the food  is always better than eating the chemical that uh has been derived from that food. because  there are other things in the food that aren't represented in that highly purified chemical  that's made often made artificially by yeast in factories. Most of them are in China uh with  all kinds of additives etc. that make it very different to just having that from uh a natural  plant. The example I like is for for years I was giving calcium replacement tablets to my patients  in rheumatology uh thinking I was helping their bones and they'd be taking you know maybe a gram a  day. It turns out that taking something like that, your body doesn't deal with it. And it's now  been associated over uh six studies uh showing that it's associated with increased risk of heart  disease and atherosclerosis with a hardening of the arteries. So the calcium is being deposited in  places that you don't necessarily want it because it's given in a form that the body's not used to.  We normally break down calcium in tiny amounts from all the foods we're eating or from mineral  waters and things like this and it's gradually gets incorporated into our body. So taking one big  dose of it uh can have very different effects on our body. So that's why I'm always wary about  supplements. They can also interact with each other. So they don't work. you know, if you have  zinc and you have iron at the same time, they they stop each other working and you don't know the  quality of them at all. And things like vitamin D, vitamin D is called the sunshine vitamin.  The body converts sunshine uh into vitamin D, and that's how we get most of it in our in  our bodies. And that's how we've evolved.

70:28 But taking vitamin D is not a replacement for  sunshine, for example, because there's many other things in sunshine that we still don't know about  that provide our bodies with a lot of benefits. And there's a lot of epidemiology comparing people  who go in the sun and out of the sun uh showing that even after having a melanoma for example,  people who go in the sun have a better immune system and a a better uh outcome than people  who are maybe just taking vitamin D tablets.

70:58 So often we mistake a subset of of a food for  being better than the whole food or the whole um environment like like sun. And there many other  examples like that where you know we just take one thing from a carrot and call it keratene and  say that's going to be good. We know carrots are good for you but if you have too much kerotene  it's probably bad for you. We love to reduce um foods to one thing. we we can manufacture that  in huge quantities. Marketing does the rest and what seemed like a good idea is often really  a pretty poor one and can often be harmful for you. If someone's offering you a single solution  to a nutrition or a gut problem, it's probably rubbish. They're probably just trying to sell you  something. But we all as humans are suckers for the the simple solution. The science of nutrition  as I've you know got into it really without biases 15 years ago is one of the most complex sciences  we have. It's we were told it was the simplest all calories and macronutrients. Turns out it's  really complicated. That means there isn't one single product or solution to it to it. There  isn't one vitamin that's going to cure you.

72:16 We need to take a more holistic view of it.  And that's that's a really important message. We need to be doing things that aren't just for a  six- week diet, aren't just to lose weight. It's how do you change all your habits that you've  you've accumulated all these bad habits. How do you change them in this direction going forward?  Uh and do this for years so that your body is much healthier, your brain is much healthier. We make  hundreds of food choices every day. And the food choices we make are the most important choices  we can make for our health. So make them wisely.

72:57 Want to support the channel? [music]  Join the Big Think Members community where you get access to videos early and free.