70 Percent of Your Immune System is in Your Gut – What You Eat Matters

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So many of the health problems we face in modern life are caused by, or exacerbated by, gut health issues. That’s because at least 50% of what makes you ‘you’ is microbial. More importantly, 70% of your immune system resides in your gut. That means when microbial populations are unbalanced, or the immune system is overworked, it can cause havoc and we see a burst in chronic illness, inflammation, brain fog, tiredness and pain. That’s why what we put into our bodies really matters. In this episode we’re going to look at:

✔️ An introduction to the microbiome
✔️ Why this the ‘alien’ world (inside us!) is so important
✔️ How essential it is to take care of your gut and gut lining
✔️ What you can do (and avoid!) to help boost your health

Disclaimer: Please note, this is for informational purposes only. Gut Heroes does not offer medical advice. We are all different and what works for me may not work for you. I setup Gut Heroes to share information with you. To shine a light on my own personal discoveries (as I currently understand them) and to help you with your own personal research.

Transcript of this Episode

Today I’m going to look at something that I find absolutely fascinating.

We’re going to look at the immune system, the gut, and in particular the gut lining, and the world within your body known as the microbiome. There is more than one microbiome, and we’ll go into that in a moment.

The key thing is we’re going to talk about the different roles and interplay between all of these and why it’s so important to be careful about what we put in our bodies.

At the moment, on the Gut Heroes website, the tagline at the top is “70% of your immune system is in your gut, what you put in your body matters.”

I feel really passionate about this because it’s only really in the last 20 years or so that we’ve become hyper-aware in microbiology about how significant a role the gut and the microbiome play on our overall health.

I’ll start with an absolutely crazy stat: 50% of the cells in your body are alien. They’re non-human cells.

At the moment, that’s the best guesstimate that scientists have. At one point, they thought it was as high as 90%+.

Basically, you have your human cells, and all these incredible microbiota which live within you as a human, in your body, on your body, literally everywhere there is life, and that consists of lots of tiny microorganisms – bacteria, viruses, fungi, archaea, eukaryotes. They are known collectively as microbiota, and they’ve evolved with us since our existence on the planet. They’ve been there a lot longer.

For some of these species, we live symbiotically. They help us. For the most part, they just exist. Obviously, there are more negative ones (for us) which can cause infections and problems and sickness. However, there are others that help us process foods and things we encounter in the environment, and they convert them into energy.

They’re essential. We could not survive without them.

If you didn’t have a microbiome, particularly a gut microbiome, you would die. You would not be able to exist out in the world. There is often a feeling that anything that’s bacteria or anything that isn’t human is some sort of germ that needs to be got rid of and cleaned. Actually, a lot of this stuff is absolutely essential to life.

The key thing when we’re looking at how to stay healthy, fit, full of energy and stave off illnesses and feel great is about figuring out how to maintain the best balance and how to have less of the things that cause problems and promote the things that don’t. That’s the central tenet of what I’m trying to create with Gut Heroes.

Going back to that original stat, 50% of your body is made up of microbiota, and that’s not in terms of size or weight, that’s literally in terms of the number of cells. You have tens of trillions of these microbiota, and they have all of these cells. You have human cells as well, and obviously cells that make up things like bones are larger and heavier. When we talk about the composition, we’re literally talking about the numbers.

That doesn’t mean that they should be underestimated because they all have different genetic makeups, and they can have really outsized effects. Size of these critters doesn’t mean a thing. They are extremely powerful in conjunction with our health. Where do they live? This is one of those crazy light bulb moments when you piece the bits together.

There are several microbiomes within the body. You’ve got, for example, the ocular microbiome (the world of microbiota that lives in your eye and interacts in your eye). You’ve got a skin microbiome (the microbiota that live in your skin – that could be fungi, bacteria, all sorts of things. Some of them help us, some irritate us, and so on). All around the body, you have these different microbiomes.

However, the key one is the gut microbiome because that is where, again, this is an estimate because we’re dealing with trillions of different microorganisms, but somewhere between 90 and 95% of the microbiota in your body lives in your gut. That’s huge.

The bit that makes you or constitutes half of you as a human being lives inside your gut.

There’s an obvious reason for that, which is that so much of what they can thrive off and live off is coming in through food and water and everything else, and that’s coming directly into the gut, so it’s a great habitat for the vast majority of these microbiota.

The next piece of the puzzle and the thing that makes this so relevant to modern life and particularly to anyone who’s feeling unhealthy or having poor health outcomes or who has an autoimmune disorder – anything where their body is out of sync and not feeling as it should – is that 70% of our immune system resides in our gut.

The immune system defends us against pathogens, so it’s defending us against harmful bacteria, sickness, all of that kind of stuff. It acts as that defence unit inside our gut. It operates elsewhere, but 70% is in our gut because it’s having to manage those populations.

A big part of what our immune system does is help control that overall population of microbiota and ensure it doesn’t get out of whack because for us to survive and be alive and do what we have evolved to do, there needs to be a balance in the populations. If you’ve got too much of a negative one, a negative bacteria or fungi, you’re going to have problems. You’ll see someone getting really sick or infected.

The big role of the immune system is to police that population in the gut.

Hopefully, this is giving you an idea of how important the things we put in our bodies are.

If the vast majority of the microbiota in your body lives in your gut and if the vast majority of your immune system is operating inside your gut, if there are problems with the gut itself or problems with the microbial population, you’re going to have all sorts of problems, and this has a snowball effect of issues.

Typically in medicine, in years gone past and still to an extent today, what we do is treat the symptoms. Someone’s experiencing pain or having trouble sleeping or staying awake or whatever it is, we develop and prescribe a pill or an injection which will stimulate the body in the short term, and it will give that kind of solution that feels like something’s working.

It is working for a time and can be essential, but it’s not tackling the root cause. A lot of the time, for many people, the issues are revolving around the gut, what’s going into the gut, what’s happening with the immune system. That’s why it’s so important to be aware of this.

The next piece of this puzzle is the gut lining.

By gut lining, I’m talking about the protective barrier that exists between your gut and the contents of your gut specifically and the rest of your body. This gut barrier is thin and vulnerable. In some places, it’s only one cell thick. If there’s a breach in the gut barrier, there can be real problems. It’s not supposed to be some sort of unbreakable fortress.

It has tight junctions and these regulate what passes through into the bloodstream and what doesn’t. Obviously, you want the positive nutrients to pass through because that’s essential for us to survive and live and thrive, but you also want to keep the harmful stuff out.

The problem is when you have issues with that gut lining where it’s too easy to breach, and when the immune system is overworked or getting confused or overwhelmed, you’re going to get all sorts of problems and disruption.

All this leads us to something called intestinal permeability, sometimes known as ‘leaky gut’.

We now believe this is very common in people with autoimmune disease in particular. I think it’s probably often undiagnosed. What it means is what I just talked about, where the gut lining becomes damaged and allows bacteria and toxins and even undigested food particles to leak into the bloodstream.

What you have happening there is a massive inflammation trigger, and you get changes to the gut composition, and then you can have something known as dysbiosis. Dysbiosis is a big one and something I’m going to talk about probably quite a lot in upcoming podcasts and articles.

It means you’ve got an imbalance in your gut microbiota – that population of microbiota, bacteria, fungi, all the other microorganisms in your gut (some of which can be helpful and some not).

That population is getting out of balance. You’ve got too much of one, too little of the other, more of the bad, less of the good. When this happens, it can contribute to leaky gut, promote inflammation, and damage the gut lining directly as well, and this can wreak havoc.

When we see these substances leaking, that’s when we can see things like chronic inflammation. Typically, that’s been linked to a whole heap of health conditions that have absolutely exploded in the modern age, including autoimmune diseases (Crohn’s disease, rheumatoid arthritis, ankylosing spondylitis like I have, celiac disease – I’ve just mentioned a few there, but dozens and dozens of different disorders), irritable bowel syndrome as well.

Increasingly, we’re finding it’s not just these diseases we’re familiar with, but also things like potentially even mental health issues as well. It’s essential.

That’s why diet is such an important factor because what you put in your body, what you eat and what you drink massively influences that composition of what’s in your gut. The different populations of microbiota are going to change according to what you eat.

For example, if you’re having only one type of food, one type of input, that’s going to massively benefit certain bacteria, certain microbes over others, and then you’re going to get an imbalance. If it’s the kind of foods that spark problems in your body, start damaging the gut lining and overworking the immune system, you’ll get massive inflammation, chronic pain, all sorts of health issues.

That’s why we need to look at what the big food producers are giving us, take stock of what we’re putting in our bodies, and see what works best for us.

What’s good and what’s bad is going to be different for everyone. There are some general markers, though. For most healthy people, things like foods that are high in fibre are good, and for almost everybody, prebiotics and probiotics (which is something we’ll cover in a future episode) are beneficial. These are things that can support what we believe to be some of the most beneficial gut bacteria.

On the negative side, perhaps the easiest to identify and hopefully eliminate from your diet are ultra-processed foods. This is anything that comes in a packet and has more than three or four ingredients, specifically anything you don’t recognise. I quite like this term (I’ve stolen it from someone else): anything your great-grandmother wouldn’t recognise is probably going to be an ultra-processed food.

These are ingredients developed in labs. We don’t know the long-term effects, but we are starting to see that ultra-processed foods are causing huge amounts of health issues without a doubt.

There’s a direct correlation, and often these ingredients are high in sugar, trans fats and additives, as well as all of these unknowns. These directly damage the gut, messing with gut permeability and causing leaky gut. If there’s one thing you do, it would be to completely cut ultra-processed foods out of your diet. The evidence is overwhelming how bad they are for us.

I used to eat ultra-processed foods every single day, multiple times a day, and it accelerated my autoimmune disease.

When I was on that diet, I felt rough. I was exhausted, inflammation was through the roof, I was in pain all the time, and the ankylosing spondylitis was rapidly accelerating. One of the biggest parts for me in now managing my condition almost completely through diet, as well as through exercise but mainly through diet, was getting rid of ultra-processed foods. I don’t miss them at all anymore, and it’s easy to spot them.

If a product has a colourful label or several ingredients on the back, it’s probably going to be an ultra-processed food.

At the very least try to cut down on them, but ideally, completely cut them out. If you do you’re going to have a massive boost in health outcomes.

The next thing I wanted to mention was NSAIDs (non-steroidal anti-inflammatory drugs).

These are drugs like ibuprofen and a number of other anti inflammatory drugs and painkillers. They can be effective and important sometimes as short-term pain management. If you are experiencing a lot of inflammation in a region and the inflammation is not being dealt with in some way, that can lead to worse health outcomes so they can be a crucial part of managing a condition.

However, taking these drugs like ibuprofen is really damaging to the gut. They cause massive irritation and inflammation to the gut lining. The way I visualize it is like throwing mini grenades at the gut lining. You will tackle that inflammation in the short term, which is great, but what you’re doing long-term is eroding away that gut lining.

If you can find other ways of reducing inflammation (things like heat exposure, sauna, cold exposure, or changing the foods in your diet), that will be a massive boost. You’ll tackle two things at once – you’ll start rebuilding your gut lining, making it healthier, and you’ll readjust the population in your gut so that you’ve got more of the good microbiota and less of the bad.

We’ve got a few more things to avoid.

We’ve tackled non-steroidal anti-inflammatory drugs and ultra-processed foods. The next one, which I’m not very good at avoiding, is alcohol. A little bit is fine, but if you drink to excess, that causes inflammation and damages the gut lining. Try to be sensible with alcohol.

Then we have stress, which is arguably one of the most under-talked about, under-targeted elements of health in the modern age.

We only ever seem to talk about it in terms of mental health – we all know if you’re feeling chronically stressed, then it can make you feel miserable, anxious or depressed. However, what we don’t talk about is how stress itself, particularly chronic stress, physically impacts your health.

By chronic stress, I’m talking about worrying about things in the future that might never happen or worrying about things in the present that you can’t quite tackle or solve – maybe you’re doing a job where you feel a lack of meaning or you’ve got a boss who makes you feel anxious, and there’s this constant stream of stuff that you have to work through, and you’re worrying about bills you have to pay, all of this kind of stuff. This chronic stress that runs through your mind, the rumination, the anxiety, physically impacts your health. It directly impacts your gut lining and, as a result, affects the gut microbiome.

It’s essential to try and get on top of stress levels. I know that’s easier said than done because we can’t always pick the job we’re doing or what’s happening in our lives at a given moment.

One of the key things to identify with stress is that when we talk about stress, it’s not the immediate important stresses that come into our lives (maybe stress involved with something happening with your child or something you encounter in the day-to-day, or maybe you’re faced with quite a scary situation and you have to deal with it and tackle it, or maybe you’re encountering a physical stress).

Those kinds of stresses, where we have to problem-solve and deal with it, are healthy. The human body and the human brain have evolved to deal with that. It’s the chronic stress, typically when we’re dealing with more abstract ideas and issues that never quite go away and are constantly there like this horrible background erosion, that we need to address.

If you can do any work on that in terms of finding ways of giving yourself some space, whether that’s going for a walk in nature or talking to someone or spending more time around loved ones and putting the other stuff into perspective as best you can, that will help.

Stress alone can trigger an episode for people with adverse health conditions and autoimmune diseases. It’s that important. I and many people I know with autoimmune disease can do everything by the book in terms of diet and exercise, but then this big stress comes along, this feeling of lack of control and anxiety, and that can trigger a massive flare – physical debilitation. It’s horrendous. Do what you can to stay on top of your stress levels.

The next one many people will already know about is antibiotics.

Antibiotics are one of the most amazing modern miracles and incredible lifesavers, probably one of the biggest lifesavers we’ve ever come across. However, they are also natural-born killers. We put them into the gut, and they will hopefully help clear an infection or help us get rid of something we don’t want. But they also can often act a bit like napalm – you take an antibiotic, and while we try and specialise as much as we can, they are going to kill a lot of healthy stuff as well. They’re going to kill stuff we don’t want to lose in terms of population, and it’s this blanket bombing.

This is going to cause us some more of that gut dysbiosis. We’re going to get rid of stuff we want, and it’s also going to affect the gut lining.

In terms of antibiotics, obviously take them if you need them, but if it’s a case where you and your doctor feel something would probably pass if you didn’t take antibiotics and if you can let your immune system deal with it naturally, always try to take that option if it’s safe to do so.

High sugar diets are another big one – sugar is massively inflammatory and can promote the growth of bacteria and yeast and cause all sorts of problems in the gut. You’re going to find high sugar in ultra-processed foods and soft drinks by the gallon. Do what you can to avoid things that are high in sugar.

Things that are safe for sugar intake are fructose (sugar you can find in fruit). If you can, eat fruit naturally. Try to avoid blended fruit because that changes the food matrix, and what you’re going to get is a massive concentration of sugar in a way that your body can’t process. When you eat an apple, for example, your body and microbiome have evolved

When you actually eat an apple, for example, your body is evolved to, and your microbiome is evolved to, process that in the best way possible. That’s the way to go in terms of sugar intake.

Then, related to that, you have artificial sweeteners, which have become popular on the basis that too much sugar is bad for you and has become a sort of target market for the big food producers. However, the problem is they’re often producing these artificial sweeteners using ingredients that are even worse. Be really careful with these.

There are an increasing number of studies showing that these artificial sweeteners can negatively affect your gut microbiota and alter the gut’s microbial composition. In general, I would avoid artificial sweeteners. There are other ways to sweeten things – you can use honey (that’s going to be much better for you) or a type of monk fruit sweetener, which can be far less tough on the gut. There are different ways of getting that sweetness into the things you’re eating or drinks.

It’s not to say that all sugar is really bad. Refined sugar is not great, but in small quantities, it’s not going to kill you. However, the main things, like the popular soft drinks that we all know have several spoonfuls’ worth of refined sugar in them, are having this massive concentration going into your gut. It’s changing the composition of the microbes in your gut, damaging the gut lining and causing inflammation – a perfect storm of bad things.

When we try to remove that by introducing artificial sweeteners, which have effects that are even worse or as bad in some cases, it just causes more problems. When you’re looking for sweetness, think of things that occur in nature naturally – honey, molasses or fruit, all of those things that you might encounter in the real world.

Then we have food additives in general, which I touched on earlier. Those are things like the binders, fillers, emulsifiers, preservatives and artificial colourings. Again, you’re going to find those in ultra-processed foods.

We’re finding lots of evidence to show that this massively disturbs the gut microbiome, increases intestinal permeability and so on. The good news is that the last few I’ve talked about – sweeteners, high sugar, all of that kind of stuff – most of that is tied to ultra-processed foods. That’s where you’re going to find most of these problems.

If you’re eating foods as they come in the world, whether a mushroom, an apple, a floret of broccoli or any animal products that haven’t been processed or filled with rubbish, you’re going to get stuff which your body can cope with on the whole.

In many ways, there’s a lot of information to digest, but the solution is fairly straightforward: cut out the stuff that has these ‘Frankenfoods’ created in labs to taste better, be more addictive, have a longer shelf life and all of these things which are great for food producers and big businesses and shareholders but terrible for our health. Avoid that and focus on putting real things in your body that our microbiomes have evolved with over hundreds of thousands, millions of years.

The last one I wanted to talk about is ingredients that are going to be specifically problematic for you.

We’re not all the same. We all have different genetics and different compositions of microbiome and immune systems. A thing that might be beneficial to you or non-harmful to you might be absolute kryptonite for someone else.

The obvious example, which we’re all now aware of but weren’t just a few short decades ago, was coeliac disease and gluten. We know for these people, if they come into contact with gluten (maybe they eat pasta or bread containing gluten), they’re going to start to get horrible symptoms, really uncomfortable and quite debilitating in many ways, and fast-acting.

What we discovered was that the best and, in fact, the only way you can treat someone with coeliac disease is to say, don’t eat gluten, and when they don’t eat gluten, they don’t get any of these problems.

It’s a case of what you work well with individually with your specific composition. We will get there in terms of the science, in terms of people having DNA mapping and microbiome mapping and being able to pinpoint what the problems are. However, for many people, they won’t know.

This was the case for me – it took me 19 years to get my autoimmune condition diagnosis, my ankylosing spondylitis. I thought I had this mystery back pain, issues with something else, and the rashes and all of that stuff. I thought there was something completely unconnected, but it was all to do with this specific condition I have.

I found that for me and many others following the diet I’m following, removing starch and dairy works brilliantly well, as far as we can tell at the moment, as well as ultra-processed food, sugar and anything like that. Starch is going to be healthy for other people, so I wouldn’t recommend someone who thrives off that to start giving that up.

Similarly, the person with coeliac disease avoids gluten, but then you’ve got all these other conditions (SIBO, for example) and a whole set of different foods to look at. You’ve got FODMAPs and tons and tons of disorders connected with certain foods, triggering certain problems, creating gut dysbiosis, altering the populations of what that particular person’s genetic makeup and immune system can cope with, and what it can’t.

If you put the wrong population of microbiota in a person with a certain genetic makeup and immune system, there’s going to be havoc, and they’re going to feel tired, in pain, inflamed, physically debilitated and all of these things.

Often, it’s a case of sitting down, creating a spreadsheet and looking at what you’re eating, what makes you feel worse and what makes you feel better. If you can do that methodically, even just for a few months, you can get a good picture of what works for you.

That’s exactly what I did with my diet, and as I’ve said many times, it’s been life-changing. In another podcast, I will talk about how I went through this process myself, how I set up a food diary, and I will share the spreadsheet I made with you so that you can do it yourself.

You’ll be able to copy and paste and hopefully get on the road to figuring out what works best for you. I want to stress this doesn’t mean that this is for everyone. A lot of these conditions have only been discovered in the last few decades.

Many problems are going to be properly identified and labelled in the years to come. Really working on this and understanding all the different roles microbiota, the gut, mental health, physical health and the immune system play is so important for feeling the best version of you that you can be.

I hope that helped. There was a lot of information to take in, but the key thing is to look at your diet.

Strip out any ultra-processed foods and high sugar, concentrated sugar stuff.

Stay on top of your stress and try to take it easy where you can on overuse of anti-inflammatory drugs like ibuprofen and antibiotics where possible, where it’s safe to do so.

Be measured on alcohol.

If you can do those things, you will see profound changes. The evidence is overwhelming that if you eliminate the bad stuff, stay on top of your stress, don’t overdo it on the meds that are going to dramatically alter your microbiome, you’re going to feel so much better. I’m living proof of that.

Many people I’ve talked to have had life-changing effects from changing their diet, and I hope that can be the same for you as well.

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