Our mental state hinges on gut microbes – epidemiologist

SS: So you’ve mentioned poor diet – is there a direct link between the food that we eat and our gut microbiome and our health? Would it be fair to say that certain types of food can actually boost our defences against Covid? And if yes then what are they?

TS: At the moment, the studies we've done in 2 million people through the Zoe Covid Symptom Study app are basically looking at general patterns of association. So we can't prove one leads to the other – to do that you need to do a proper randomised control trial. So we're looking at epidemiological association. We're building this picture up but we don't have 100% proof at the moment that we can say this particular food is bad for your microbes and is going to lead to Covid but we know from other studies and we published a paper in Nature Medicine in January showing that in 1000 people we could link 15 bad bugs which are associated with poor health, with certain foods and overeating those foods. So we've for the first time just managed in this area of science to link the foods you eat, the microbes and health outcomes. But it's too early to say in Covid exactly what they are.

SS: Ok, but what about those foods that you said that were bad for us, that have bad bugs – can you just give us an example?

TS: Yeah, they're the ones that you would probably guess anyway. So they are highly processed what is often called junk foods, they are the ones with 20 chemicals in it, the ones with artificial sweeteners, extra added sugar, extra added salt, with multiple contents that don't come from whole foods, and they are generally low in fiber and they may contain things like highly-processed meats, and general poor quality foods, whereas the opposite is true of vegetables, fruits, olive oil, all the foods that we know are generally good for your gut microbes.

SS: What about supplements, vitamins, probiotics? I take probiotics, if I add more probiotics to my nutrition, will it make me more resilient to the virus?

TS: We looked at this in 2 million people who recorded whether they had Covid or not. And the studies are not clear-cut about probiotics, they do show a small effect in females, but not in males. So we suspect that could be selection bias. And the problem with probiotics generally, is that everyone has a very different gut microbe community. So you and I will only share maybe 20% of our gut microbes. So it's very hard to know why we should take the same probiotic if our communities are very different. It's like planting seeds, you know, one in Africa and one in Siberia, the environments can be different, so they won't grow the same. So that's part of the problem with probiotics, we haven't yet managed to personalise them but I think that that's definitely the future. So it at the moment is a bit of a lottery, whether probiotics will work for you or not, depending on which ones you pick. And whether you pick multiple species and how they together work in your gut.

SS: So here's a question that is very relevant to all future moms. We start building our own unique microbiome at birth while travelling out of mother's womb, right? Are kids born by C-section deprived of this very essential first dose of microbes? Does this mean that potential health risks could arise for them in the future?

TS: There's increasing evidence that's true. And we know, across most of the world, 30 or 40% of women have Caesarean sections now, it's become nearly a routine procedure in some countries. And basically, we all get our microbes from our mother, when we're born naturally and Caesarean section means that the baby is born sterile and will pick up the microbes from the nurse or the skin of whoever it is. So they'll be different in the first three years. And studies have shown that with Caesarean section, babies are more likely to have allergies, and more likely to have an increased weight later in life. So I think it is really important we realise there's a downside to Caesarean sections, it’s not the perfect operation that saves lives for many women. And also, it's another reason to emphasise the importance of breastfeeding, which is another way that microbes can get into babies as well. So the mother can transfer her microbes through breast milk as well. And that's another way of keeping the baby healthy. But definitely, the data so far is cautioning against doing too many Caesarean sections because it could lead to epidemics of immune problems or increase in weight in future generations.

SS: Can we understand the microbiome to an extent that we could be treating diseases by tinkering with it?

TS: At the moment, our knowledge is only really just starting in terms of the microbiome and the problem is that there are a few bugs that we know tend to go with many diseases but there isn't generally one bug that causes one disease like we thought genetics was like, and that's probably because, as I said, all of us are unique in our gut microbes, which means that all our microbes which are basically chemical factories, all produce different chemicals in our blood, and so I think we'd be looking to change the whole function of the gut microbes because they work as a community, it’s not as single identical species, so it's groups of them that we need to change. So, I think we're a way off doing that apart from possibly with some microbial transplants what we call ‘poo-transplants’ where you transplant the feces of someone who's very healthy into someone who's very sick and basically transplant the microbes in one person into the other. That has been shown to work in a number of diseases but in a way, it's very crude talks, we don't know what the key microbes are that are doing that and it certainly doesn't work for every disease. It only so far works for about two diseases we know very well and the rest are still in trials.

SS: Is there a link between our microbiome and our mental wellbeing? I mean, does a healthy gut reduce stress or make us feel better about life or ourselves?

TS: There is a definite link between our gut and our brains. Our gut microbes produce chemicals that affect our brain, our mood, they can change dopamine levels in our brain. Studies can regularly show that people who are depressed or anxious have poor gut microbes and when you give people with depression probiotics or you give them a healthy Mediterranean-style diet you can improve their mental state to the same extent as you can with traditional antidepressant drugs. So, I think there's huge potential for improving mental health via either diet or probiotics.

SS: Is there a connection between microbiome and longevity? Are there bacteria inside us that help us age slower or help prop up some kind of longevity gene?

TS: There probably are but we don't know what they are yet. But we do know that there is a gradual decline in our microbiome probably from about the age of around 50 and it accelerates as you get over 75 and so many people who are very elderly do have a deficiency of many microbes, and if you test people at 75 you can pretty much predict how long they will live depending on what their microbes are like. So that's why I always say testing someone's microbes is a much better idea of their health than testing their DNA because the DNA doesn't change all your life and it's not as predictive as we thought whereas your gut microbes will give you a very good prediction of what's going to happen in the next five years and I think this is going to be a really exciting area of science moving forward because the nice thing about it is unlike genes we can intervene with specific diets or with specific probiotics or other medicines to improve those microbes and reduce your risk of ageing or having other immune problems.

SS: You've done a lot of research on epigenetics as well as the microbiome. Now we know that scientists are looking into this and finding out that stressful events, for example, can actually influence the genes you have, change them and then you pass those on to your offspring. But does keeping a healthy microbiome also change genes? Say, I eat fiber, seeds, whatnot, so my gut is like pumping happy neurons in my brain, and then does that give me new happy genes that I will then pass on to my children?

TS: It's a nice thought. Certainly, in laboratory animals, there is evidence you can do that. So in lab mice, you can change both the gut microbes and the genes by changing their diet and both the microbes of the mother will be passed on to the next generation as well as the genes. So we think both are important, going forth. And I personally think the microbiome is even more important than these epigenetic changes. I've studied both. And I'm certainly now moving more towards the exciting microbiome genes rather than tweaking our own ones, because in humans, it's been very hard to study that because the changes are very small and subtle whereas the changes you get with your microbes are very big and increasingly visible. But I think the idea we can pass good health on to the next generation is definitely an important concept. But it also causes a lot of stress to mothers as well, because there's so much pressure on modern mothers now, in terms of their health, that I wouldn't want to put too much strain on them. But clearly, they need to look after their own gut microbes as well as their own genes now more than ever, and so the diet of pregnant women is really important.

SS: Now, your latest book’s subtitle is ‘Why Almost Everything We've Been Told About Food Is Wrong’ and you tackle a lot of myths about food, including those about the role of breakfast and calories, etc. Let me ask you this. Are there any commonly held ideas about food that are actually true?

TS: Yes, there are a few. 

SS: What are they? 

TS: That, in general, eating large amounts of plants is good for you. So that's, I think, the main one. And most experts even though they disagree on most things, will agree that most fruits and vegetables eaten in reasonable amounts are generally healthy for you. And most people also agree that having too many sugary drinks, candies, etc., are bad for you and bad for your teeth. But apart from that, the rest of it gets into grey areas, and you start getting many people disagreeing on whether fats are good or bad, on whether carbs are good or bad, or whether you should use diet drinks or not, whether meat is good or bad, etc. So that, but it's important to realise there is some part of nutrition everybody agrees on and that's we should be eating more fruits and vegetables. 

SS: What about good French wine? Is it considered a sugary drink? Or is it a good thing for you if you do it in moderation?

TS: Well, I'm biased because I like my red wine. So I have to claim that that's my disclaimer. But we did find that red wine has the highest number of polyphenol chemicals of any drink. And polyphenols are a defence chemical in plants that microbes love. They're basically like rocket fuel for your gut microbes. So we did a study on several thousand people in the US and the UK showing that wine drinkers, red wine drinkers had a healthier microbiome than non-wine drinkers. So I'm a big fan of red wine in moderation but not all my colleagues agree.

SS: Okay. We also hear a lot that fat and fried foods increase the risk of cardiac diseases, and therefore shorten your lifespan. Are these actually some of these, you know, preconceptions about food that are wrong? Or is there any truth to them?

TS: I think we had too simplistic a view of fat. And, you know, the American scientists started this about 30 years ago, saying fat was bad for us. And gradually, that evidence has got less and less clear as we've moved on. And what is important is to realise that there are good fats and bad fats, but also, you can have good and bad fats in the same food. So you take a really healthy food, like extra virgin olive oil, for example, that everyone agrees that's healthy, but there's 13% of that is saturated fat, but because it also has lots of other good fats in it it's healthy. So the evidence that if you just had lots of artificial transfats, that you might find in really cheap cookies or fried food is bad for you, that's probably true. But in general, there's nothing wrong with fat.

SS: Like a great Angus steak with a bit of fat that comes as a crust when you fry it or grill is a good thing for you?

TS: In moderation, it's a good thing. I think if you had that every day, it would not be a good thing. So it also depends on what else you put on your plate. I couldn't find anything to say that people who have small amounts of meat regularly have any health problems at all. If they have plenty of plants on their plate as well, plenty of diversity. So really, all the new evidence is pointing that we shouldn't just isolate one thing as good or bad because it depends what else you replace it with. If you replace fat with refined carbs, like potatoes or rice, then actually, the replacement is worse than the fat. But if you replaced it with beans, and lentils, and salads, and other healthy Mediterranean-type products, it would be a good change. So it's very outdated, this idea that, you know, low-fat foods are good, high-fat foods are bad. Actually, the food companies have made sure that they make cheaper and even more low-fat products that are probably worse for us than the originals. And so this is why we have to change our concepts. You know, it's not all about ‘fat good’, ‘fat bad’, ‘carbs good’, ‘carbs bad’. It's much more complex than that. And it does depend on everyone getting back to understand what is good quality food, what's a balanced diet, and it's not about these three macronutrients, because food is actually 30,000 chemicals. It's not three things. And this is what the complexity of the science is now showing us and it's a very exciting time, but we have to really rethink the whole area.

SS: Apart from the food and what to eat, there's also a question of when, right? Some say it’s best to eat little but often, others say, “Do not eat after 6 p.m.” There's also this really popular thing of intermittent fasting when you choose not to eat between 6 p.m. and 12 p.m. next day. I remember talking to this famous oncologist, David Agus – maybe you know him? – and he told me that it's much more important to have meals the same time every day and nothing in between meals. What do you think makes more sense? Which theory?

TS: Well, I think that the old theory that we should eat little and often is rubbish. That was based on an American study about 30 years ago of 10 people. And that was the idea that you just wanted less stress on your body so you kept it nourished all the time. But we now know that having long fasting intervals is better for your metabolism. So we should have less snacks and more serious meals, move away from the US model of six meals a day, go back to perhaps two main meals a day, plus or minus breakfast. And that's because the gut microbes do better when they have a rest of at least 12 hours. And it's easy to do that overnight but it could be any other time because the health of your microbes improves if they have a rest that they can then clean your gut wall and they're metabolically much healthier. The other reason is that we were always told, certainly in the UK, that breakfast is the most important meal of the day. I don't know about Russia, but most mothers tell their children, “You must eat breakfast before you go to school, it's really important, you know, for everything.” And some people are not hungry in the morning when they wake up. They just don't feel like eating and yet we force people to eat. And our studies have shown with this company Zoe and this Predict studies that two-thirds of people do metabolise better in the morning, but a third of people metabolise better in the evening. So actually, it's personalised. And I for one metabolise my food better in the evening than in the morning. So that really means I should have a bigger evening meal and skip breakfast or have a lighter breakfast most days. So I think people need to experiment themselves about what works for them, rather than being told that there's one size fits all.

SS: So you're saying two main meals a day, one light meal, whether it's breakfast or dinner or lunch and no snacks in between?

TS: That's what the science is telling people. Yes.

SS: Does it matter what time you eat breakfast? Because I've also heard like, “Oh, you should eat it really early in the morning!” or “You shouldn't eat your dinner later than 6 p.m.!” Or is it also very personal?

TS: Yeah, that sort of advice is ignoring the fact that everything's now personal, and that we all have different circadian rhythms. There are morning people, evening people, and also you change with age. You know, I'm sure we're seeing that people as they get older, metabolise less well in the mornings and better in the evenings. And all the studies were based on young, you know, 20-year-olds, and so can't be applied to most of the population. So I think people need to experiment and what makes them feel better, you know, listen to their own bodies. And increasingly, there are commercial tests out there that people can do at home, to work this out. Things like continuous glucose monitors and other personalised kits that you can get to see how your personal metabolism is at different times of the day. And this will be mainstream within five years.

SS: All right, Tim, it's been such a pleasure talking to you, very, very interesting. It's a topic that always fascinates me. I wish you all the good luck with the new research. And I hope this microbiome science becomes huge much sooner than we expect because I believe in it.

TS: That's great. It's going very fast. And I think the key is that if we can change the way people eat and they think about it, they're not just eating for themselves but they're eating for their microbes, then, you know, we can make a big difference.

SS: Thank you a lot, Tim. Have a great day. 

TS: Thanks. Bye.

SS: Bye.