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First published by Thorsons 2020

FIRST EDITION

© Dr Jenna Macciochi 2020

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Source ISBN: 9780008370268

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Dedication

To Luca and Isabella who have given me so

much in such a short time.

And to all those who believed in me when

I struggled to believe in myself.

A Brief Note to Healthcare Professionals

In this book I have sought to present some of the current and big ideas in my field, fusing them with my own stories, personal anecdotes and my passion for this subject. My aim was also to convey a sense of wonderment for this silent system and the vast and complex science it encompasses. I am acutely aware that this is not – and could never be – an exhaustive text on the immune system. In my attempt to keep the narrative and scientific ideas as clear as possible for the general reader, I could not cover all the topics I wanted to or discuss them in the depth they may warrant. And rather than present a complete textbook-level description, I have deliberately chosen to focus on the broader contemporary issues – to bring an awareness to how modern lifestyles and our rapidly changing environment interact with and shape our immunity and, ergo, our health. In my quest to be evidence-based I have dived into the scientific literature, consulted with colleagues and reached out to other experts along the way, combining this information with case studies and alternative health literature to give a balanced and holistic overview. In some cases the only ‘evidence’ available is weak or at least not the most rigorous, so I have made efforts to state this where appropriate. Ultimately, any one book can only tell part of a story and this, I hope, is just part one.

Contents

1  Cover

2  Title Page

3  Copyright

4  Dedication

5  A Brief Note to Healthcare Professionals

6  Contents

7  CHAPTER 1: How to Be Well in a Modern World

8  CHAPTER 2: Living for Longevity

9  CHAPTER 3: Have Your ‘Old Friends’ Got Your Back?

10  CHAPTER 4: Sleep, Seasonality and Circadian Rhythms

11  CHAPTER 5: Mental Health Matters

12  CHAPTER 6: Intelligent Movement for Modern Life

13  CHAPTER 7: Immunity-nourishing Nutrition

14  A Final Word

15  References

16  Further Reading and Resources

17  Acknowledgements

18  Index of Searchable Terms

19  About the Publisher

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CHAPTER 1
How to Be Well in a Modern World

‘There is no permanent ideal of disease resistance, merely the shifting sands of impermanent obsolescence.’

MATT RIDLEY, author

Described by the US National Library of Medicine as ‘the most complex system that the body has’, our immune system is a vast constellation of cells and molecules spanning every nook and cranny of our bodies.

WHAT’S IMMUNITY AND WHY SHOULD YOU CARE?

‘Immunity’, from the Latin immunis meaning ‘exempt’, refers to the art and science of the human immune system – the various biological defence systems that keep us well. The immune system is a silent wonder. While we are very aware of our hearts beating and the breaths we take, we are much less aware of our immune system and the many jobs it performs to keep us well. This mighty system protects our health by resisting uninvited infections, maintaining order and balance in our bodies, and healing wounds. It is our foundation to wellbeing.

Immunology, the extraordinarily rich, yet complex study of the immune system, has changed the face of modern medicine over the last 30 years. There has never been a more fascinating time to delve into immunology and harness its power to improve your health. And that is what this book will do for you. Based on cutting-edge, evidence-based scientific research, this book takes you on an empowering journey through the latest astonishing discoveries in immunology. You will get to know the immune system inside out and come to an intimate understanding of how it works.

It is not often that one body system touches so many aspects of human biology in both sickness and health. Although it is seemingly esoteric and beyond comprehension at first blush, the immune system is the epitome of versatility and simplicity of purpose.

When it comes to maintaining good health, the immune system is our most precious asset, yet we rarely appreciate our essential defences until something goes wrong. We thank our immune system when we catch a cold and scramble for vitamin C supplements in the winter months. But what about all the other wonders it works? If it only existed for the first few weeks of chilly weather every year, we’d all be in serious trouble. Most of the time our immune system is working away in the background and we don’t even notice it. Deeply entwined with every aspect of our physical and mental health, it lays the foundations of our health and longevity.

Immunity is a sophisticated system, with astonishing complexity. But there is a lot that can go wrong, from autoimmune diseases and allergies, to mental-health problems and metabolic issues – even cancer. We have an obsession with looking healthy and being well, and yet we are sicker and unhappier than ever before. That’s because our delicately balanced immunity is easily compromised by our ever-accelerating pace of life, with its relentless stress, pollution, overconsuming and under-moving. What modern life deems ‘healthy’ may not actually be so. Today, we’re more likely to die from a lifestyle-related disease than any other cause, and many of these would be preventable if we took better care of our health.

On our journey through modern immunology, you’ll discover why the immune system is your sixth sense, connecting your health to your environment, feelings and emotions; why some people rarely get sick; what to do if you have a chronic illness; and what it really means to ‘boost’ your immunity.

My endless wonder at this vast and elegant system, integral to our wellbeing, has been the driving force behind both my career and personal life. From an early age I was intrigued by the human body, health and disease. My mum, a trained cook, strongly believed that health was in our own hands and taught me the old-fashioned cookery basics that have become a vital tool in my modern-day mum–life toolbox. She was the original purveyor of old wives’ tales. Yet there was a wealth of untapped wisdom in her words that left me with a lingering curiosity, shaping my path as I embarked on my scientific career.

As I’ve discovered more about the immune system, I’ve found myself changing how I live in response to what I’ve learned. I’m driven to question what modern life tells us is healthy, yet makes our immunity go awry. Every day I find myself hunting for clues, researching the evolution of the immune system and thinking about the traditional ways of life that have shaped our health. Have we thrown the baby out with the bathwater by swapping old ways for new and shiny modern ones? This is a question I keep coming back to, and one which I’ll answer in the chapters that follow, while also exploring how we can reclaim our innate knowledge of immunity through traditional rituals, supported by science. Keep in mind as you move through the chapters that the immune system is a bit like a wiggly moving octopus. Its undulating nature makes it difficult to cover it in a linear, page-by-page fashion. And one of its slippery charms is that the answer to many questions about it begin with ‘It depends’ or ‘It’s complicated.’ Understanding the secrets of how to be well requires a balance between openness to new ideas (no matter how counterintuitive they may seem) and ruthless scrutiny of all concepts both old and new.

Despite its immense power, we often hear calls to ‘boost’ our immune system through food, exercise or a wellbeing practice. Although there remains much to learn about its interconnectedness and intricacies, to function well the whole system requires balance, not boosting. Read on as I explain what this means for your health.

INFECTION PROTECTION

The immune system is all that stands between us and the hordes of microbes (also known as germs, these are microscopic organisms including bacteria, fungi and viruses too small to be seen by the naked eye) that threaten us constantly. Hippocrates (460–377 BC) was the first to find a scientific explanation for disease. His was the theory of the four humours (yellow bile, black bile, phlegm and blood) in the body – the idea that these were in balance in healthy beings, but out of balance in a sick person. Sickness, he claimed, was the result of an excess of one of the humours, caused by miasma (poisonous vapours or mist filled with particles from decomposed matter) or miasmata (vapours coming from decomposing organic material such as waste, manure or dead bodies). This theory may sound strange to us now but reflects the limited tools and technologies available at the time. Without a way to ‘see’ germs, scientists didn’t have much to go on. In the mid-19th century, as equipment for poking and probing evolved, ‘germ theory’ – devised by Louis Pasteur (the father of immunology) and his contemporaries – emerged and soon replaced the four humours in public consciousness. Germ theory is how most of us think of immunity: germs are bad, and immunity’s white blood cells are our guardian protectors. But of course, nothing with health and immunity is ever that simple.

Immunity is hard-wired to detect and differentiate between what is us (self) and what is foreign (non-self), such as a germ. This makes it easy for our immune system to decide what to attack: non-self potentially dangerous germs that need eliminating, (normally) sparing our own precious tissues.

The immune system has had a complicated, you might even say fraught relationship with germs over the years. For centuries we have drawn a causal conclusion that microscopic germs cause illness – and for good reason. Devastating outbreaks, infection epidemics and perplexing illnesses have all been caused by the veritable smorgasbord of micro-organisms that we share this planet with. Over the last decades our fear of them has been realised, with devastating reports of swine flu, Zika, Ebola and many others – each outbreak prompting new concerns about infection protection. But from birth to death we are silently bombarded, minute by minute, with an untold number of potential infectious threats. Whether we get sick or not is decided by the integrity of our immune system. Most of the time, our immunity deals with these germs without us even knowing about it. That’s how powerful the system really is. There are no medications that can protect us in our infectious world quite like our immune system.

THE IMMUNE SYSTEM: A REALLY, REALLY, REALLY BRIEF EXPLAINER

Though vastly complicated and mind-bogglingly confusing, as any of my immunology students will tell you, let’s try and keep it real simple.

The immune system is not, in fact, one thing, and it’s not in one place. Rather, the immune system is a whole galaxy of cells known as white blood cells (leukocytes, to give them their proper name). Immunity also includes lymphatic organs (such as lymph nodes, bone marrow and spleen), molecules (cytokines) and their collective array of biological functions. The bone marrow is your immune-cell factory where new immune cells are born from stem cells – a blank-canvas cell with the capacity to evolve into any one of your numerous immune-cell types. Despite their name, white blood cells are not just found in your blood, but in strategic locations all over your body. Every single one of them brings its own particular skill set, featuring an array of receptors and molecules capable of inducing the many different flavours of an immune response.

Border Control

A good way to start understanding the immune system is to liken it to a castle – a fortress with many layers of defence, all working as a close-knit team. Your body’s borders act as the first line of immune defence: skin and the mucus membranes that line your natural openings – such as your mouth, nose and digestive tract – are part of your immunity, making and releasing substances that create a hostile environment for the invaders or attacking and destroying them directly. These physical barriers are as delicate as they are protective, with inherent vulnerabilities, and over the millennia just about every germ that wants to get in has evolved ways to help it do so. In response, our immunity – or castle – has devised a sophisticated system, choosing the best and discarding the least useful bits of our elegant defence mechanisms, so that every barrier surface has its own unique set of immune defences designed for that location.

Priority Setting: Full-Frontal Innate Immunity

Put simply, the cells and molecules of the immune system comprise two parts: innate and adaptive (which we will come to soon). Together, they are your body’s safeguard. Innate response is what you notice when you first get sick (inflammation is an example of an innate response). It attacks with a vigorous, feet-first approach. What our innate immune response lacks in specificity, it makes up for in speed. The starting line-up features the innate cells. Like scattered ‘listening posts’, these are diverse and everywhere in our body. They act as sensors, hard-wired to detect anything out of the ordinary, eating germs and debris, calling for backup. Legions of these innate immune foot soldiers rush to assess a problem, attack it with potent killers to defend (and potentially harm) our bodies, causing significant collateral damage to our own tissues. Our immune system’s beautiful destructive dance, with its characteristic heat, swelling, redness and pain, looks like the scene of a microscopic multi-car crash. As this happens, you may spot those familiar signs – a stuffy nose, sore throat, tummy ache, fever, fatigue or headache – and then go on to experience familiar symptoms such as increased mucus, pus and a cough.

Now, while inflammation is a vital immune response and fundamental to our health, it is, by design, only supposed to be an acute, short-term assault. This is because it is as damaging to our own tissues as it is to invaders. Triggered incongruously, it can cause problems long after the initial danger is gone. As we’ll explore, inflammation is core to our modern-day health niggles, existing on a continuum: from mild symptoms such as weight gain and fatigue at one end, to heart disease, depression and autoimmune conditions at the other.

The Path to Resolution

When we are sick, the body needs inflammation. But if this response continues for too long, it becomes counterproductive. The imprecise inflammatory defences discharged by innate cells can wreak havoc on our delicate tissues and even on entire organs. The immune system needs at some point to reduce the inflammation and has therefore acquired the tools to regulate it. So how does inflammation lessen? Let’s explore.

Acute inflammation and all its associated chemical weaponry also upregulates many anti-inflammatory mechanisms to temper the fire. Special pro-resolving mediators (signalling molecules) are naturally produced in the body during the process of inflammation. And they, ultimately, close the loop on the whole process. Rather than turning the immune system off (and risking infection), resolution works in collaboration with inflammation, letting it do its job before gently inviting back the status quo.

Common over-the-counter anti-inflammatories such as ibuprofen or acetaminophen (paracetamol) block important pro-resolving signals, inhibiting the way our bodies naturally resolve inflammation. This is why they are not recommended as a long-term treatment. Aspirin, on the other hand, does not block but gently attenuates, while also stimulating resolution – which is why it is sometimes recommended at a low dose for certain inflammatory conditions. Resolution of inflammation might not seem like such a big deal, but it’s paradigm-shifting, with vast potential to aid our modern-day health crisis, controlling chronic inflammatory disorders and promoting wound healing. We can support the resolution of inflammation in other ways too, which, as you will read, may be our best chance during future health challenges.

Slow and Specific Wins the Race

Innate immunity is pretty darned good at quickly detecting and eliminating potentially harmful germs, sensing and repairing damage, and quietly removing old or malfunctioning cells. But although it provides immediate protection against intruders, it is incomplete at best. When stressed to the limit, it has to call on its big brother: adaptive immunity.

If innate immunity is an initial shotgun blast at all the bad guys, adaptive immunity is a targeted missile. It’s a second-line defence that takes a while to kick in – some five to seven days. Unlike innate immunity, which can involve a veritable horde of white blood cells, adaptive immunity is controlled by the lymphocytes. There are two categories of lymphocytes, known as B lymphocytes and T lymphocytes. T lymphocytes are the master controllers, sent out into the body, controlling the levers of many other arms of immunity; B lymphocytes are our special reconnaissance unit – the antibody producers.

Each of us has a unique repertoire of T and B lymphocytes, adding a layer of individual exclusivity to our immunity and, consequently, our health. An immune system that doesn’t produce a huge variety of unique T and B lymphocytes will probably miss or ‘not see’ certain germs or viruses, and these could go on, unchallenged, to cause disease. This happens during ageing, for example as we will explore in the next chapter. Adaptive immunity is a remarkably effective process. But much like the innate inflammation response, when it is improperly triggered, it’s equally bad for our health, as we’ll see.

Blurring the Lines

To fight off infection and disease, the innate and adaptive parts of our immune system collaborate to detect and destroy anything recognised as foreign or dangerous in the body. We first need to co-opt the innate immune system to capture germs and present them via some oh-so-important compatibility molecules (more on these in a bit) to T lymphocytes waiting in anticipation. The innate immune system is an ingenious doorbell that awakens the adaptive immune response with germs in a format they can recognise.

T lymphocytes then swing into action, cloning themselves into huge armies to maximise their fighting power and differentiate into specialised subsets – driving, fine-tuning and sometimes regulating other immune cells – to maximise the chance that intruders are eliminated at minimal cost. Lymph nodes bring B and T lymphocytes together with innate cells at the right place and time. This is why your lymph nodes become swollen when you’ve got a cold coming on.

Collectively, the immune system is, in fact, a model of versatility rather than rigid divisions. Feel those swollen lymph nodes next time you have a sore throat and congratulate yourself on successfully linking the innate and adaptive immune systems.

How Is Your Memory?

Innate immunity is vital for life, but it only has a short-term memory. So instead of mounting a faster and more effective response upon encountering a known trespasser, it starts sluggishly from scratch each time. The adaptive immune system, however, is like a library of ‘memory’ cells. Information on every virus, bacteria or fungi that ever invaded your body and was defeated by your immunity is archived by this immune system, identifying them by their molecular shape. This is called immunological memory. And it almost never forgets!

Memory cells do not actively fight the current infection. They patrol the body in case of future infection with the same germ, so when we face that same disease-causing germ, this retained memory means we know how to defeat it – often even before we’ve experienced any symptoms. This explains why you only catch certain diseases once, such as (in most cases) chickenpox, despite repeated exposure. More cunning viruses, however, like influenza and rhinovirus (the cause of the common cold), have developed sneaky ways to evade our immunological memory by continually changing their molecular information.

Natural Born Killers

Natural killer (NK) cells are, as their name suggests, killing machines. Unlike T and B cells, these are not produced in response to a specific antigen (toxin). Instead, they recognise changes in our own cells. These cells are crucial to our health, rapidly responding to kill our own cells when they get infected with a virus.

NK cells are our bodies’ main cancer-surveillance tool. With specialised receptors, they patrol the body inspecting each cell. They respond to newly formed tumours and abnormal growth of our own cells. And they also decide the fate of a pregnancy. NK cells represent 10 per cent of white blood cells but are also found dotted around the body in various places including the liver, lungs and lymph nodes – like your very own Special Forces regiment, with a smaller number of troops but just as deadly as an entire infantry division.

Really Tolerant T Cells

Military metaphors can be a useful way to describe our immune defences, but only when we use them in a nuanced way. The immune system is more sophisticated than a ruthless defender using brute force. It is, perhaps, more of a peacekeeping force, seeking a steady, harmonious state, not a constant battleground. Although it focuses on tossing out the bad guys, it must do this while causing as little damage as possible. This is to avoid damaging our precious tissues.

So who guards the guards? At the top of the peacekeeping chain are T regulatory cells, known as Tregs. Tregs control or suppress other cells in the immune system, fighting substantial fires and making sure the other cells toe the line. Tregs are designed to send a signal that immunity should withdraw, pause an attack and stand down.

Without these regulatory cells and molecules, the state of inflammation that helps destroy threats would lay our bodies to waste. Tregs are crucial to the overall balance of our immunity. They maintain tolerance to ‘good’ germs, prevent autoimmune diseases and limit inflammatory ones. But they can also suppress the immune system, preventing it from doing its job against certain infections and tumours. For optimal health, we require sufficient but not excessive regulation by Tregs. Imagine a small proportion of your immune system is reserved for regulation. Some of that is genetically determined, but some can be shaped by life choices like diet and exercise, stress and sleep. The system therefore operates on a constant tightrope: insufficient immunity (too many Tregs) may increase incidence of infections and cancer, while excessive ‘friendly fire’ (too few Tregs) may lead to damage to our own cells and organs.

Vaccination – The Great Teacher of Community Immunity

Vaccination is one of public health’s greatest success stories. Yet it also has become one of the most contentious areas of health policy over the past two decades and few things are more divisive in immunity than vaccinations (see Chapter 2 for more on this).

Vaccines work on the same principle as acquiring an infection naturally. When you acquire an infection naturally, your adaptive immunity, T cells, B cells and antibodies, are primed to fight off the germ. Then, a residual immunological memory remains, patrolling your body for decades (perhaps even a lifetime), ready to protect you if that germ ever tries to infect again. Your immune system reacts to the vaccine in a similar way to being invaded by the disease itself. Introducing a bit of weakened virus or bacteria teaches the immune system how to deal with it. It generates a memory response so when the real germ comes along, an army is at the ready. Just as each germ is unique, each vaccine is too. The memory produced by vaccines is different for each type. This is why some require booster shots – because vaccines don’t 100 per cent replicate the natural course of an infection, they (mostly, depending on the vaccine) don’t all provide the same degree of immunological memory.

Why Do Some People Never Seem to Get Sick?

In my job I like to practise what I preach. Most of the time I pretty much have my health nailed down, but each year I still catch the odd cold or bug. The average adult will get two to four colds a year, but some lucky people claim never to catch a cold or take a day off sick. We’ve all met them, whether it’s through family or at work – they breeze through cold and flu season without so much as a sniffle. What is their secret? How can we be more like them?

Your immunity is unique to you and determined by several factors. Genetics plays a part, but not in the way you might think. We each have around 25,000 genes, but your genetic code only differs by about 1 per cent from that of the person next to you. You might think that the majority of these differences are related to why we all look different, varying our hair colour, height or personality. But, aside from our brains, the genes that vary most between us are, in fact, a tiny cluster that plays a disproportionately large part in our health. This gene cluster is called the human leukocyte antigen (HLA), also known as the major histocompatibility complex (MHC). Let’s call these genes the ‘compatibility’ genes for short.

Our compatibility genes encode our immunity, yet they are as changeable as the pathogens (bacteria or viruses) they aim to prevent. These molecules have evolved to come in a variety of shapes and sizes. They mutate with each generation, unlike any other genes in our bodies, in an effort to track the ever-changing infectious threats we face. Our immunity depends on their combined performance. Our compatibility genes flag viruses and bacteria, and present them to the immune system for eradication. The fact they come in a range of shapes and sizes, prevents a virus or bacteria from mutating and then evading the immune system in every person they infect.

These special genes tell us a lot about the intricate balancing act essential for not only our health, but the survival of our species. Humans are incredibly similar but also fundamentally diverse, and compatibility genes are the key to our individuality. Simply put, if all our immune defence systems were identical, a single deadly disease could come along and wipe us all out. But this ingenious process comes with certain trade-offs. For example, we can’t easily exchange our body parts; if you have ever received an organ transplant, you will be familiar with the lifelong challenges involved in stopping your body rejecting the new tissue. In fact, immunity that works wonders for protecting one person can be quite deadly in the life of another.

Compatibility genes are the reason why we all fare differently when faced with the same infection. You may have inherited a set of compatibility genes that are expert at dealing with one particular virus – the common cold, say. This does not mean that your immune system is better or worse than mine; just that yours would deal better with fighting the seasonal lurgy. But when it comes to a different type of germ, I may fare better. And it’s not just our individual susceptibility to infection that is affected by our own unique combination of compatibility genes. For example, there are genetic variants in immune compatibility genes which protect some people from the HIV virus but leave them with an 80 per cent chance of getting a horrible autoimmune disease called ankylosing spondylitis.

Like our fingerprints, immunity makes us truly individual. The inherent diversity in how our immune systems respond to different diseases is an entirely deliberate design by mother nature without hierarchy. While the world is busy arguing over the physical, visible differences between people, our immune compatibility genes don’t discriminate. No one has a better or worse set. It’s the collective diversity that’s crucial. This diversity has been carefully crafted by evolution. Millions of years of evolution have more or less tuned our immune system to be running optimally. We might not be able to become completely resistant to disease, but it’s why we haven’t all been wiped out already.

Our immunity has been in place for around 500 million years. Its history goes so far back that we share it with other jawed vertebrates. And it has remained largely the same ever since it first evolved. Our immunity is millennia old, shaped and polished by evolution, and, by virtue of this, it is very good at what it does. The fact that our immune system is largely untouched by evolution is a testament to how important and effective it is and always has been. Evolution is not a predetermined design process; rather, it is one that advances in fits of trial and error as well as chance and necessity. Your successors will carry in them not only the final product of these efforts, a one-and-only perfect immune system, but also the marks and remnants of many immune systems.

If the Immune System Protects Us, Why Do We Still Get Sick?

Most of the time, our bodies win the fight against germs, but sometimes they lose. People who ‘never get sick’ may catch a slight cold now and again or suffer an occasional ache and pain. This makes sense when you realise that we live in a microbial world, and the microbes were here first.

Microbes haven’t only threatened our health, they have shaped it. They were the first traces of life to appear. And much later on, from within those early microbial ecosystems (and never separate from them), larger multicellular organisms evolved. Including us. And we have never quite separated from them.

Now we know that there are up to 1 trillion microbial species on Earth, and only a minute fraction of them cause disease. So vilifying all microbes for the sake of a few is a mistake, and possibly one of our biggest (you’ll discover why in Chapter 3). Nevertheless, much of the fear of microbes lingers in the public consciousness. As I mentioned, it’s quite normal to get up to four minor infections (like a cold) each year. But as infections are beaten back by modern-day sanitation, vaccination and antibiotics, we now have huge increases in ‘non-infectious’, lifestyle-related diseases. As you will read, this is no coincidence.

Let’s look at how infection spreads. Take rhinovirus, the cause of the common cold, for instance. Roughly one in five people carries the rhinovirus at any given time in the tissues of their nasal passages (the prefix ‘rhin’ in Greek literally means ‘the nose’). To infect you, these germs need three things:

 A way to get out of the reservoir (the person sitting near you who is sick)

 A mode of transportation to a new home (that person sneezing – a sneeze produces 40,000 droplets and you can get infected by inhaling just one)

 A way to get into their new home (you)

Another classic route for the spread of germs is poor hygiene, especially inadequate hand-washing. Bacteria are passed to everything we touch. But simply being a thorough hand-washer with good personal hygiene helps you stay healthy and avoid illness-causing bacteria. And while we can’t account for how infected people behave around us and we can’t control for the immunity genes that we have inherited, we do have some control over the various lifestyle levers we can pull to get the best out of our defences.

Nature Versus Nurture

Like fingerprints, immune systems vary from person to person. We all inherit a unique set of immunity genes – but this is just an instruction manual, and while the code can’t be changed it can be interpreted in many ways. You can help train and maintain it. Epigenetics (the study of how our genetic code is interpreted) is manipulated by many lifestyle factors. An example of epigenetics might be the changes in something called DNA methylation. (Essentially, methylation is like handcuffs for a gene, marking that gene as not to be used. If certain genes are methylated, then a cell might not be able to turn on critical functions and could become a cancer cell, for instance.) Various environmental factors can alter our methylation pattern, such as smoking, poor diet, air pollutants and alcohol. Adjustments in our epigenetic patterning can derail some of our vital immune responses. The metaphor used by scientists is: ‘Your genes load the gun, but environment pulls the trigger.’ Just a little immunity TLC from time to time can, for most people, keep all components functioning more smoothly.

Despite the prominent role played by genetics, immunity is not fixed by our genes. It’s continuously nurtured by our encounters and adventures, shaped by our changing emotions and surroundings, responding to how we live our lives.1 As mentioned, our immunity even has the capacity to learn and develop a memory. Collectively, this plethora of influences accrued across a lifetime determines, at any given point, if we get sick and for how long. This human ‘exposome’ is our immunobiography (more of which later), the culmination of everything that challenges our health throughout our lives, including infection, our diets, lifestyle factors and social influences. In short, it’s what we refer to as nurture (nature being the genetic part). This holistic view of health and disease goes some way to explain why some people end up being more susceptible to getting sick.

INFECTION – THE FACTS AND THE FICTION

It starts with a sniffle. Next thing you know, the whole household is sneezing, coughing and passing tissues. Before long, the common cold, or worse, the seasonal flu, is upon you all. Wondering how you can dodge those germs or ‘boost’ your immunity? With so much conflicting advice out there, it can be difficult to know what to believe. So let’s start by putting myths to rest with a simple guide.

No. 1 Tip to Avoid Infection

In the mid-19th century, a Hungarian man called Dr Ignaz Semmelweis made an important discovery. He linked childbed fever among women who had just delivered their babies in the hospital to the failure of the doctors who delivered those babies to wash their hands after performing anatomical dissections of the dead. The key to reducing infection was simple: wash your hands. Semmelweis died before his theory gained support, but hand-washing remains a cornerstone of modern-day infection control.

Most People are Infectious Before They Get Symptoms

Before the onset of symptoms, a person may already have an infection. How this works depends on the germ in question. Respiratory viruses are best engineered to spread when you have physical symptoms; the more symptomatic you are, the more you sneeze and cough, the more likely you are to spread an infection. But sometimes you can infect others with a virus even when you are asymptomatic. For influenza, you are infectious one day before symptoms and five to seven days after their onset. Young children and patients with altered immune systems can spread the virus for longer periods of time.

It’s Just a Mild Cold – Am I Less Infectious?

Just because you have mild symptoms doesn’t mean the virus is mild. It may just mean that you lucked out with your compatibility genes for that particular germ and your immune system is able to control the infection. For this reason, it’s important to remember that even with minimal symptoms, you can still infect others and potentially make some people really sick, especially those who are vulnerable, including the elderly and very young.

Why Do Colds and Flu Strike in Winter?

The flu season in the UK starts in October and is in full swing by December, generally reaching its peak in February and ending in March. For our Antipodean cousins, the season is flipped. Put simply, whenever and wherever there is winter, there is flu. Even the word ‘influenza’ may be a clue – its original Italian name, ‘influenza di freddo’, means ‘influence of the cold’.

A common misconception, however, is that flu is caused by cold temperatures. This is not quite true. Flu is caused by the influenza virus. Cold temperatures simply create conditions that make it easier for the virus to spread. Scientists now know that the influenza virus is transmitted best at cooler temperatures and low humidity. So the viruses that cause the flu survive better in winter and are able to infect more people. Another reason is the lack of sunlight and the different lifestyles we lead in winter months: days are colder and shorter during the winter, so we spend more time indoors and are more likely to share air with someone who’s infected. Lack of sunlight leads to low levels of vitamin D, a key immune-nourishing nutrient. Having less vitamin D decreases our immunity’s ability to fight the virus.2

You’ll Catch a Cold from Being Cold

‘Put on a jacket or you’ll catch a cold.’ I’m sure you were told this as a child, but nowadays it is usually dismissed as an age-old misconception. Much like the previous point, it’s the virus, not the temperature, that makes us sick, right? Well, yes. But it turns out that this advice contains a kernel of truth too. It has been shown that when you are exposed to the cold for a prolonged time you may not be able to launch the most robust immune attack. While this effect might be marginal in most healthy people, older people, young kids or those with underlying health issues may have an even harder time fighting off the virus. So, best heed your parents’ advice and bundle up when heading out in the cold! Wearing a scarf in winter does warm the air in the back of your throat, making it less hospitable for those seasonal viruses that prefer cool air.

Disease Symptoms Are Sometimes the Immune System Doing Its Job

You might have heard that bacteria, viruses and fungi are the cause of disease symptoms, but often this is technically incorrect. Disease symptoms mostly occur because your immune system is at work reacting to trespassing micro-organisms with inflammation.

Take the example of the common cold. Your immune system jumps into action when the cold virus (rhinovirus) invades the epithelial cells that line your airways. Immune system chemicals dilate your blood vessels and increase their permeability, allowing proteins and white blood cells to reach the infected tissues in your nose, sinuses and throat. However, this causes nasal congestion. Additionally, you may get a runny nose because of the increased fluid leakage from your permeable capillaries, combined with increased mucus production triggered by the immune response itself. Then there is fever.

Through evolution, we developed fever as a response to infection. Raising your temperature makes most germs less efficient at multiplying and helps your immune cells work more effectively. There is evidence too that fever even improves the ability of antibiotics to kill bacteria.3 Awareness of this phenomenon has given rise to two appealing, but conflicting, schools of thought. One theory is that fever is a natural part of the immune response to infection, so we shouldn’t interfere with it. The other is that fever is a potentially harmful consequence of infection, so we should suppress it to minimise any complications.

What does science have to say about these conflicting theories? There is actually little evidence that fever itself, even a high one, is harmful.4 Unless you are really uncomfortable, have difficulty breathing or have a fever lasting more than a few days it’s normally wise to avoid fever-reducing medications like paracetamol or ibuprofen as they are not without side effects. The immune system can still get its job done if you take medicine to reduce fever, but slightly less effectively – and taking it won’t speed up the process.

Over the Counter

No one wants to stay at home feeling miserable with a cold or the flu. And sometimes you just can’t. So what about all those over-the-counter (OTC) cold and flu medications? Most OTC cough syrups are not effective for adults or children,5 and the NHS now recommends honey rather than cough syrup. OTC cold and flu medications won’t ‘cure’ or even shorten your cold or flu, but there is some evidence that they may provide some symptom relief in adults. Each time my husband catches a cold, he treks to the pharmacy, spending (wasting) lots of money searching out a cure. Perhaps the idea that he is proactively looking after himself makes him feel better about the situation, which may create a little placebo effect. But the pills he buys won’t cure his cold.

Reducing symptoms is, however, often desirable, or necessary if life demands that you function. So if work really can’t wait, which product is best for your symptoms? Here’s the lowdown:

Antibiotics definitely don’t help and shouldn’t be used for the viruses that cause colds and flu. Cold and flu tablets may contain decongestants, pain relievers, antihistamines and cough suppressants. So think carefully about your main symptoms when selecting a product and read the label carefully – avoiding taking medicine you don’t need reduces the risk of side effects. Decongestant tablets can have effects beyond the nose and may exacerbate other medical conditions such as high blood pressure. Speak to your pharmacist before taking these medicines.

When it comes to immunity there are few quick fixes. The minor benefits from certain treatments need to be weighed up against the risk of side effects and the cost of the medicine. There are a few nourishing ways to ease a cold without pharmaceuticals but rest really is the best medicine. If only you can step off the treadmill of life for long enough.

DO YOU NEED AN IMMUNE ‘BOOST’?

If a well-functioning immune system is key to living a longer and healthier life, then the idea that you can boost your immune system is certainly enticing. Searching ‘immunity’ online or walking through the aisles of any health-food store reveals an abundance of nutritional supplements, cold remedies and fortified foods all promising to ‘boost’ your immune system and, by doing so, to stave off colds and flu. But is there any scientific truth in these claims?

Sadly for consumers of these ‘immune-boosting’ products, the notion of the immune system as some kind of internal force field that can be easily ramped up makes little sense scientifically and is one of the biggest misconceptions about immunity that I come across in my work.

Because of the way your immune system is designed to work, you definitely wouldn’t want it to be boosted. Taken literally, the term ‘immune-boosting’ is an unfortunate one. Rather than a single binary on/off switch, the immune system is more like a series of switches – a rheostat requiring constant tweaking to get it just right. Attempting to ‘boost’ the cells of your immune system is complicated. There are so many different kinds that respond to so many different microbes in so many ways. Which should you boost? And how much? So far, there is no single answer.

Researchers have looked at whether things like echinacea, green tea, garlic and wheatgrass supplements can help us see off germs, but existing evidence in support of a single immune-boosting nutrient or superfood is not strong. If you are looking to strengthen your immunity, the best way is through a combined approach based on the information in the following chapters’.

NOT ALL GERMS CAUSE INFECTION AND NOT ALL DISEASE IS FROM GERMS

Not all germs are bad and not all disease is caused by germs. Although germ theory still dominates how we think about immunity, we know that things are more complicated than that.

The Danger Theory of Disease

It would be nice to have a simple, clean separation: immunity doesn’t react to our own harmless ‘self’ molecules, but only to things that are not us – i.e. harmful ‘non-self’ germs. But is this the case? Are all harmful, non-self, immune-triggering molecules from infectious germs? To complicate matters further, not all diseases are caused by foreign germs (take allergies, for example). And not all germs in the body warrant destruction (the microbiota say, that you will meet in Chapter 3). Various aspects of our day-to-day lives involve interaction with something non-self – and many are things that we don’t want our immune systems to reject: mothers don’t reject foetuses; we tend not to attack the food we eat; and we don’t reject the millions of microbes living harmlessly, and often helpfully, on and in us. All these are examples of foreign ‘non-self’ things that somehow evade the immune system’s wrath. Yet non-infectious immune diseases related to modern lifestyles are rampant. Until relatively recently the field of immunology was agnostic as to how this happened. Then, along came Polly.

While for decades we wrongly assumed that the immune system could simply spot self and differentiate that from non-self, a 20th-century immunologist rewrote the script. Born in 1947, Polly Matzinger blazed an unconventional trail. Following stints as a bass player, a dog trainer, a carpenter, a biology student – and later a Playboy bunny – she went on to change our understanding of how disease happens, poking holes in the dogma and becoming one of the most influential thinkers in the field. It turns out that immunity is not just concerned with whether the thing it is reacting to is self or non-self; rather, it is also hard-wired to detect patterns of danger.6 Why is danger relevant? We can get sick in the absence of an active ‘non-self’ infection. Which means that something is still triggering the immune system when germs are absent. This trigger, Polly discovered, is a pattern of danger signals from our own cells and tissues.

In fact, we even have a term for this: danger-associated molecular patterns (DAMPs).7 Danger comes from any change in our cells and tissues, such as damage or stress, and can even be from lifestyle-associated molecular patterns (LAMPs).8 The immune system’s smoke detectors sense something is awry. This triggers a series of molecular signals which bring about an immune response. One example of how this happens is when inflammation occurs in the absence of any germs.9 We call this sterile inflammation. You might have experienced this, as I did recently after tearing the ligaments in my ankle. No broken skin and no infection, but immediate swelling and visible inflammation as my painful ankle ballooned and bruised. The missing ‘danger’ link in this situation is in part due to the mitochondria in our cells. The sheer mechanical tearing up of tissues (like when I twisted my ankle) releases the contents of our cells into the blood, including their cellular battery packs, the mitochondria, which are distant cousins of bacteria. In terms of our immunity, this means they are molecularly ‘non-self’, despite being part of us. Why is this important? Well, inside our cells, mitochondria are shielded from our immunity, but when they leak out, they are recognised (by innate immunity) as patterns of danger. Their bacteria ancestry makes them exceptionally good at signalling to start inflammation, even though no infectious germs are present.

Sixth Sense: Immunity Beyond Infection Protection

Understanding infection protection was the first step in discovering how the immune system works, and it remains the main lens through which our immunity is viewed. But infection protection is only part of the story. Vigilantly patrolling, our health guardian is always on. Beyond just surveying for possible infections, immunity has many additional vital functions: it governs repair and healing, regulates body weight and metabolism, defines how we age and if, or when, we might encounter age-related disease. Immunity also determines the success of a pregnancy or a transplanted organ. And, crucially, using those NK immune cells you met earlier, it is our main cancer surveillance system. The immune system is so fundamental to our existence, it’s the essence of our species.

People often talk about having a ‘sixth sense’, a way of perceiving the world other than by the standard channels of seeing, smelling, tasting, hearing or touching. I’d like to propose that your body has such a sense: the humble and hard-working immune system deserves recognition as a sensory organ of sorts. Much like vision, hearing and touch, our immune system recognises challenges from our environment and signals from our emotions. Unlike other types of cells, immune cells can sense and respond to environmental, hormonal, nutrient and even brain signals. This dynamic ability makes the immune system both fairly unique and quite peculiar.

In fact, science has started to consider immunity as a kind of second brain: a specialised network of biosensors designed to pick up information from within and around the body and relay it to the brain, where it can motivate and manipulate us to behave in specific ways. This may be as simple as huddling, shivering or sleeping – actions that are typically considered general symptoms of illness or debilitation, but may, in fact, be highly specific and beneficial responses to infection. In other cases, the immune system may inspire behaviours not typically associated with illness at all, such as passivity, aggression or sexual attraction. The immune system, it would appear, has quite a bit to say not only about how we behave but about how we feel and even who we are.

Instead of recognising light, sound waves or taste, the immune system recognises molecular shapes of germs, damage or danger – perturbations to our status quo. Sampling the environment, immunity has evolved rigorous mechanisms enmeshed with all our other body signals to keep us well. No other system in the body places such a premium on adaptability (except, possibly, the brain – and why would nature disconnect two such vital systems from one another?). If our immune systems can’t counter the diversity in our ever-changing environment by adapting and responding, we’re dead ducks.

Although it may sound counterintuitive, immunity keeps you alive, but is also disease-causing. Tip it one way, and your immune system weakens, leaving you vulnerable to pathogens. Tip it the other way, and it becomes overactive, attacking your own healthy tissue or benign things in the environment. Or it becomes unable to regulate the daily inflammatory wear and tear. These are not things you want.

Modern Malaise

Illness is part of our natural history – a biological heritage, crafted by evolution, the greatest part of it prior to the antibiotic era. Pre-antibiotics, infectious disease had the potential to wipe out the majority of us. This created evolutionary pressure to mount strong immune responses. But now, mostly everyone in the Western world survives the childhood infections of times gone by. As we humans have evolved, so too have our diseases. Over the past hundred or so years, deaths related to infectious disease have been dramatically reduced. But the diseases that have challenged us have also shaped us and left us with deeply embedded evolutionary vulnerabilities. And while epidemics of diphtheria, plague, cholera and smallpox no longer sweep across the Western world, we now have other foes to fight.

Today, germs are no longer the enemy. In fact, 99 per cent of those that surround us at any given moment (and they are everywhere, all the time) do not cause disease. Rather, they are ‘good’ bacteria – our microscopic health allies. This pokes holes in the ‘all-germs-are-bad-and-should-be-avoided’ dogma. These microbes were here first and our long-shared history with germs has cultivated an enduring marriage of mutual exploitation (we’ll explore this further in Chapter 3). The spectrum of disease faced by our immunity today has changed considerably from the infectious ones that challenged our health in the past. Germs may no longer be the main enemy we face but the war on our health certainly isn’t over. We have merely delayed and mostly transformed it.

Of all the major health threats to emerge, none has tested the foundations of public health so profoundly as the rise of chronic non-communicable diseases (NCDs), which include autoimmunity, allergy, metabolic dysfunction and some cancers. Immunity has a central role to play across the spectrum of these chronic conditions that have quickly replaced infectious diseases as the leading cause of premature death and disability worldwide. We are getting sick in the absence of infection – the Western world is experiencing a rising tide of lifestyle-related illnesses, with immune-triggering danger signals rife and immunity going awry. This trend is deadly, carries crippling economic costs and cannot be easily reversed under the conditions of our 21st-century lifestyle. While an infectious disease can spread fast and far and kill irrespective of age, complex modern NCDs are long-term conditions that develop silently over years – even decades in some cases – ending the lives of people still in their prime, figuratively if not actually killing them. But we should remember that for all the ways in which we seem to be sliding backward, we’re lurching forward too. Since the 1980s, in Western countries we have sharply cut down on deaths from infections and malnutrition. Thanks to medical advances, rising wealth and much else, infectious diseases now kill fewer people than non-communicable ones. Sounds like great news, right? Well, it would be. But we have simply replaced one with the other, to the detriment of our health.

The good news? Doctors, scientists and the general public are increasingly aware that this is happening. Getting a handle on your health earlier in life might just be the key to better outcomes for these long-term chronic conditions. But although these modern-day health challenges are linked heavily to lifestyle, we cannot ignore how life in the 21st century also makes it difficult for people to change what they do. We can ban smoking, clean the air, build cycle lanes, tell people to eat ‘5-a-day’, but it’s not always easy for people to alter their behaviour, and this is a big part of foiling non-communicable diseases. It’s also one reason why these diseases don’t always generate the same level of concern: they’re often regarded as the sufferer’s fault.

Autoimmunity: Friendly Fire and a Case of Mistaken Identity

You may have heard of autoimmune diseases – but what exactly are they? And who gets them?

Autoimmunity is like friendly fire – a condition in which the immune system is too active, and unchecked T and B cells grow overzealous, wreaking havoc on the body they’re supposed to protect. The body has a variety of fail-safes to ensure that the immune system doesn’t attack itself, the guardian Treg cells being a mainstay. But sometimes these safeguards don’t work or get weakened and we get an unwarranted inflammatory response towards ourselves.

The incidence of autoimmune disease is increasing worldwide by up to 7 per cent every year. Autoimmune disease is a large umbrella term, and there are over 80 diseases within it that are linked in some way. Each of these can be terrible, frustrating, debilitating and hard to diagnose. They are driven by the adaptive immune system with its long-lived memory, making them impossible to cure. Some of the most common ones include type 1 diabetes, rheumatoid arthritis and lupus.

The causes behind autoimmunity remain broad and murky, but what we know for sure is that there is rarely a single cause. In fact, some research suggests that all of us have a little autoimmune potential as a trade-off for having over 100,000 unique T and B cells, each with the potential to detect a different molecule. This gives us a broad-spectrum infection protection but at a potential cost, in that some of these white blood cells might mistakenly recognise molecules on our own cells. Most of the time our specialised immune regulatory systems act as a firewall that keeps any rogue cells with autoimmune potential in check. Any issues with immune regulation leave us wide open to any counterintuitive attack. A big clue that this is the case lies in the fact that people who develop one autoimmune disease are more likely to develop another, indicating a global immune dysregulation is at play throughout the body.

Genetic predisposition accounts for roughly 30 per cent of all autoimmune diseases and currently there are more than 20 associated genes, many of which are in the ‘compatibility’ genes. This goes a long way towards explaining why autoimmune diseases tend to run in families. One family member might have rheumatoid arthritis, one might have thyroid disease and one might have lupus. It might be the same gene causing each of these different autoimmune conditions. But then identical twins are identical in genes, but they are not identical in developing autoimmune disease. This tells us that genetics is just part of the picture.

The remaining 70 per cent of autoimmune diseases are the result of environmental triggers and other situations we encounter – for example, toxic chemicals, diet, infections, digestive issues, stress and other lifestyle factors. Exposure to the perfect storm of non-genetic factors may actually flip the switch to push the immune system in the direction of an autoimmune condition. These factors are referred to as the ‘mosaic of autoimmunity’. And to complicate things further, each of us is different. So the particular combination of factors that causes one person to develop an autoimmune condition may not do so in another. In other words, there’s no one recipe for autoimmunity.

In the following chapters I will explore some of the ways that we can reduce our risk for autoimmunity. None of these lifestyle modifications is a guarantee to prevent or stop autoimmune disease. But together they may help to lower your risk.

A big issue with treating autoimmunity is that the slow-burning symptoms take so long to become apparent, and by the time they do, your immunity has silently been damaging your tissue for years. If you are unfortunate enough to be diagnosed with an autoimmune disease, you’ll probably be told that it’s incurable but manageable. Many of the current therapies for treating autoimmune diseases work by suppressing the entire immune system and are likened to using ‘a cannon to swat a fly’. Consequently, while these therapies can successfully block an inflammatory response, they have the unwelcome side effect of leaving patients vulnerable to infection. Though there are many essential conventional therapies now available, I’ll share some complementary approaches to treatment throughout the book.

Allergy – The Scourge of Modern Life

Allergies are the close cousins of autoimmunity. They are the result of the immune system overreacting – not to us, but to benign things in our environment like pollen (in the case of hay fever) or to a specific food (such as peanuts). Allergies are immunity overshooting, creating inflammation in the body in response to something that doesn’t really pose much of a threat.

Our ancestors didn’t suffer from allergies, and anyone from Generation X will recognise that they were extremely rare even a few decades ago. In fact, before the 1990s, peanut allergies were so rare that there was barely any data on them. Incidence of allergies is now steeply climbing, showing no signs of abating. Like autoimmunity, this happens partly through genetics. Our collective population genes have changed little over this relatively short period of time, so can’t be to blame. It is likely that these modern-day epidemics are due to an environment and lifestyle that do not allow our immune systems to properly calibrate.

ALLERGY: A HISTORY OF A MODERN MALADY

In the 1880s British doctor Morell Mackenzie noted that hay fever, with its tell-tale summer sneezing through the pollen season, went hand in hand with culture. Hay fever was an aristocratic disease, implying that the higher we rise on the socioeconomic scale, the more this allergic reaction tends to develop. Medical science at the time deduced that hay fever was the result of the stresses of modern life, the cry of an immune system struggling with its environment, and Mackenzie went on to conclude that the typical patient was ‘a delicate, upper-class only child who subsequently developed into an emotionally and socially maladjusted adult’. In fact, although there are many influences involved, levels of urbanisation may be one of the strongest predictors for the prevalence of allergy in a population, both historically and in the future. This has been shown time and time again. Allergies are more likely to affect people who are more distanced from traditional upbringings. The history of allergy is perhaps a metaphor for our physical, emotional and cultural responses to our changing environment.

Cancer – A Nasty Trick on Our Immune Defences

Cancer is a wide range of diseases with a common characteristic: something goes wrong in the way the cells regulate growth, resulting in uncontrolled cell expansion. This happens deep in the cell at the molecular level, in the cell’s genetic material.

Cancer is somewhat a matter of odds – an unfortunate by-product of the way evolution works. Large and complicated animals like us humans are vulnerable to cancer precisely because we are large and complicated. Each time our cells replicate, there is a chance of a mutation. Some of these mutations are benign, some are useful, but others are dangerous. Though it may seem flawed, over generations we pass on tiny mutations in our genes via this system. These mutations select out certain physical attributes, or phenotypes, to our offspring helping them better fit their environment. This is natural selection. But natural selection is not natural perfection. The more replications, the higher the chance of cancer. This is why our risk for some cancers increases with age. As previously mentioned, our immunity is our main cancer-surveillance system. But cancer is ‘self’. It is part of us. So it can easily slip under the radar of our immunity cancer patrol. This is the cruel trick cancer plays on our immune defences. Some cancer cells present ‘Don’t-eat-me’ signals on their surfaces, instructing our immune cancer killers not to attack our own tissues.

While there is much evidence that exercise and healthy living can reduce the risk of certain cancers, reducing is not preventing. You cannot remove all risk. Lifestyle can have a huge influence on the risk of cancer overall. My dad – an active man, a farmer, non-smoker, rare drinker, never overweight and having never eaten a takeaway in his life – was diagnosed 12 years ago with colon cancer, one of the most preventable lifestyle-associated cancers. With a colostomy and chemo (and a lot of faith in Mother Nature) my father survived the illness and has enjoyed good health since then. But, as I write, my family and I are anxiously awaiting more information on my dad’s second cancer diagnosis.

Other than hereditary risk (mutations passed down in your family), and certain exposures and behaviours (like smoking), cancer is still pretty unpredictable. The older you get, the more likely it is that you will have it, and you might not even know it. And not all cancers have known lifestyle components. Even with the ‘perfect’ diet and lifestyle you are still at risk. But this doesn’t mean that making healthy choices is futile. In fact, around 1 in 4 cases of cancer could be prevented in the UK each year largely through lifestyle changes including stopping smoking, maintaining a healthy weight, eating a healthy diet, enjoying the sun safely, protecting against certain infections and cutting back on alcohol.10

When it comes to cancer, the good news is that taking care of your health will help you get through treatment and recover in better shape than your less health-conscious peers. From the earliest days of my dad’s cancer diagnosis, my mother instinctively stepped up her game to prioritise his wellbeing. Not a lifestyle overhaul, but paying attention to the little details: tweaks to his diet to ensure as much variety as possible and plenty of protein, prioritising sleep and reflexology to aid with the stress of such a diagnosis.

Metabolic and Lifestyle Disease

Metabolic syndrome – a cluster of metabolic aberrations that results in conditions combining diabetes, high blood pressure and obesity – is rampant. This clustering of risk factors doubles the risk of heart disease and increases that of type 2 diabetes five-fold. Research also links metabolic syndrome to an increased risk of several cancers. The diseases associated with metabolic syndrome can be chronic, debilitating and lethal. Even though each metabolic condition is different, these diseases share common features below the surface. Metabolic disorders are caused by a multitude of factors, but the immune system plays a role. Metabolic syndrome has strong inflammatory underpinnings often associated with deregulated immunity and reduced infection protection.

Something in our lifestyles triggers immunity danger signals that feed into metabolic deregulation. Many people with metabolic syndrome are overweight. Being over your healthy weight does put you at risk of metabolic derailment. In our modern environments it’s easier to over consume calories, sending immunity slowly awry, as we will explore in Chapter 7. Studies suggest that this link reflects the influence of chronic inflammation and elevated levels of hormones involved in metabolic processes, like insulin. But weight doesn’t tell the whole story, as we will see. The modern Western lifestyle hasn’t just changed our diet, but every facet of our way of life. Epidemiological studies confirm that most people affected by metabolic syndrome have multiple common lifestyle characteristics or behaviours. These include smoking, poor diet, obesity and physical inactivity – all identified as leading contributors to overall mortality, working together to increase the risk of chronic conditions and other negative health outcomes in adolescence, adulthood and old age.

Brain Immunity

Until recently, the brain was thought to be cordoned off from the peripheral immune system. It’s carefully tucked away behind a barrier to give it extra armour and prevent germs from getting in. But that extra barrier means that while most germy threats can’t invade the brain, the body’s immune system can’t easily get in either. So it is reliant on its resident immune police-force cells called microglia. These cells patrol the brain. They swallow up invading germs, chow down on dead neurons and also trim the ends of healthy ones. (Neurons are specialised nerve cells in the brain, whose ends connect to each other, passing messages back and forth. These conversations help us to learn movements, store memories and much more, but the cellular connections change over time. Some become stronger. Others weaken. Eventually, some old connections aren’t needed any more. So microglia step in as the neurons’ personal barbers, pruning off old, less useful connections at the ends of cells so that new ones can emerge.) This single type of immune microglia in the brain exists in multiple flavours, working as versatile all-rounders, not specialists. So when they go rogue (following serious infections, injury or psychological trauma) they play a key role in mental-health problems and neurodegenerative diseases that rob people of their minds, memories and the ability to go about their normal lives.

Studying the relationship between mental health and the immune system is a hot area in psychiatry and neuroscience; so much so that new terms have been coined to define the field: psychoneuroimmunology describes the bidirectional communication between the brain and the immune systems and immunopsychiatry is the biological dominance of the immune system in the brain–body relationship. Inflammation was once considered a passive bystander in the health of brain function. Advances in science are beginning to unearth an unexpected role of the immune system in disease onset and pathogenesis. As we will explore, research suggests that for tens of millions of people, certain neurological disorders might be caused by a malfunction of the immune system. In other words, it is not ‘all in the mind’.

A New and Dangerous Form of Inflammation

The discovery in the 1990s of a ‘new’ form of inflammation present in many, if not all chronic diseases goes some way to explaining the surge in our modern-day malaise. A subclass of inflammation, often termed chronic or ‘meta-inflammation’, is now used to define a form of low, smouldering inflammation. Unlike the short, sharp assault acute inflammation delivers, meta-inflammation is a long-term slow burn. It is not local to any specific area, but widespread, silently surging through your veins. New links between inappropriate inflammation and seemingly unrelated disease or disorders emerge in the medical arena on almost a weekly basis.

When inflammation shifts from short- to long-lived, there is a breakdown in immune tolerance and regulation, and major alterations in the normal functions of all our cells and tissues, increasing the risk for all non-communicable diseases. Chronic inflammation can also impair normal immune system functioning, leading to increased susceptibility to infection, tumours and poor responses to vaccines.

When someone is experiencing chronic inflammation, the causes are insidious, the ‘danger’ triggers are so subtle and the root issues can be difficult to pinpoint. Shaped through evolution, in an environment in which sedentary behaviour was minimal and calorie surplus was rare, immunity is not optimised to our present lifestyle. One of the first red flags for chronic inflammation was its link with obesity. But this slow burn can also be present without someone being overweight – it’s just the cumulative effect of our overall modern lifestyle, comprising a plethora of psychosocial and environmental factors. Modern living has disturbed the balance of the immune system, setting off the ‘danger’ alarm bells in the form of an inflamed molecular cascade. This reaction is slowly undermining our health, constituting a cause or complicating factor in many diseases. We may not even realise, until slowly the cracks start to show.

Silent Signs and Symptoms

When you experience acute inflammation, the symptoms are pretty obvious: redness, heat, swelling and pain, all localised to the site of the injury or infection – like a sprained ankle or sore throat. But the symptoms of chronic inflammation are a bit more subtle and sometimes not even there at all. Signs that chronic inflammation is manifesting in your body include:

 Erratic moods, anxiety and depression (inflammation affects your entire body, including your brain)

 Pain (one of the key features is often painful, stiff or achy joints)

 Fatigue (inflammation places demands on your body, messes with your stress response and muddles up hormonal balance; it makes sense that your body is telling you to hit the sofa rather than the gym)

 No symptoms at all, but ‘just not feeling right’ (while symptomless chronic inflammation might seem pretty chill, it can still lead to all the risks and complications of chronic inflammation with symptoms)

There aren’t, unfortunately, any standardised tests to measure chronic inflammation. A simple blood test can measure a liver chemical – C-reactive protein (CRP) – which, as part of the immune system, rises in response to inflammation. The result can help your doctor devise a strategy to lower your levels. However, the test doesn’t show where the inflammation is or what is causing it.

When chronic inflammation symptoms do present themselves, they can manifest in a variety of ways, many of which can be mistakenly attributed to a lingering common cold or something else (hence chronic inflammation being so tough to nail down). Doctor visits are often related to the negative effects of stress or just feelings of being not quite right, unexplained or ongoing fatigue or niggling aches, pains or rashes. The red flags of chronic inflammation are often only acknowledged once severe symptoms that we can no longer ignore have taken hold.

While those symptoms all sound pretty awful, there’s worse news: chronic inflammation has been linked to some very serious health issues down the line. Seemingly unrelated conditions like heart disease, type 2 diabetes, autoimmunity, allergy, some forms of cancer, and even neurodegenerative diseases like Alzheimer’s share this deep immunological link.11 This is because if it is continually ‘rescuing’ (i.e. fighting over a long period of time without resolution), your body’s inflammatory response, left unchecked and unresolved, is universally damaging to your healthy cells, tissues and organs, which, in turn, leads to damaged DNA, tissue death and internal scarring. Chronic inflammation may be a recently observed phenomenon, but many of the related diseases are themselves not new. They are the same cluster of wear-and-tear diseases of ageing, but rates are increasing dramatically. And now they are happening more aggressively and at younger and younger ages in individuals living in industrialised countries who follow a Western lifestyle. But they are relatively rare in populations who adhere to more traditional diets and lifestyles, with environments and social stressors starkly different from those typically present in today’s modern Western world.12

The idea that chronic inflammation – constant, low-level immune-system activation – could be at the root of many non-communicable diseases is a startling claim, requiring extraordinary proof. But is it cause or consequence? The details are still being fully worked out. The pathways of inflammation are complicated, difficult to define and manipulate, making unpicking the details challenging. But in 2017 a large-scale human clinical trial of more than 10,000 patients in 39 countries examined the effects of inflammation in heart disease. Researchers found that the immune system’s inflammatory response is uniformly damaging and causal in the process, killing people by degrees.13 For some conditions it appears that inflammation is a causal factor in this modern malaise. Until we accept that – and take action to change it – we will not be able to fight these lifestyle illnesses effectively.

The Drugs Don’t Work

True, anti-inflammatory drugs exist. There are many types, including non-steroidal anti-inflammatory drugs (NSAIDs), many of which are available as common over-the-counter non-prescription drugs – ibuprofen, for example. These are powerful medications for a whole variety of acute pain problems, and when taken for a few days or a week they are very safe for most people. But they are not without their side effects. The Food and Drug Administration added new warnings about NSAIDs in July 2015. NSAIDs must be used cautiously in people with heart conditions and cardiovascular problems since recent studies have demonstrated taking prescription NSAIDs for just one week can increase the chance of heart attack or stroke in these patients,14 not to mention the suite of more common side effects, including damaging the delicate lining of the digestive tract. And, alarmingly, they actually interfere with the resolution of inflammation, hindering the natural course of the healing process that our bodies are designed to do so well. In fact, these treatments may bring symptomatic relief, but a little-known fact is that they have minimal effect on chronic inflammation. Inhibiting these crucial resolution pathways over the long term induces physiologic dependence, which has been shown to produce a rebound effect, paradoxically promoting chronic inflammation further through a compensatory mechanism.15,16 Constant use actually worsens some of the problems that people hope to ameliorate by taking these drugs. Arthritis is a prime example. NSAIDs provide short-term symptom relief, but long-term use accelerates disease.17 This is why, and studies confirm this, that when it comes to chronic inflammation, the side effects might outweigh any benefits.

So when is it OK to take NSAIDs, and when is it not OK? This is a complex and controversial topic. If you have been prescribed these drugs, then you must follow your doctor’s orders. Prescriptions aside, these drugs are ubiquitous and available without prescription, so now there’s no guidance or accountability, and people are taking them for every imaginable pain or ache, even for emotional stress. They must be used with an eye towards the delicate balance that has allowed our species to survive this long. We need to start looking to better long-term ways to manage chronic inflammation, some of which we will explore in the upcoming chapters. I’m optimistic that holistic approaches to managing chronic conditions won’t negate NSAIDs but may reduce how many we need to take.

Avoiding Snake Oil and How to Get the Best from Your Immunity

By now you should be getting the picture: immunity is more than those symptoms you feel when the seasonal winter lurgy rolls around. Immunity is the river that runs through every aspect of health and wellbeing. In my experience as an immunologist, it is so central to our wellbeing – survival, even – that its inner workings offer key lessons for living better. It keeps us alive. But it can also make us sick. We can no longer ignore the fact that our fast-paced, over-consuming, unrelenting lives are slowly eroding the balance of this carefully crafted system.

In my line of work I’ve heard it all. From chicken soup for the sniffles to copper bracelets for arthritis. Old-wives’ tales, traditional beliefs and the positively bizarre. Each generation has their own ‘snake oil’ concoctions, potions or rituals promising miraculous cures and good health. Many are flawed or completely miss the mark, some are foolhardy and others downright harmful. That’s not to say all alternative remedies are ineffective. Often, they seem to work for the people who promote them but may not be appropriate or are perhaps even dangerous for others. And, certainly, most won’t be enough to keep you healthy all the time. For some, the biology of belief is enough. By this I mean the placebo effect, which is a wondrous thing. It shows us the immense power of our minds and the beliefs we hold, even though the impact that mindset can have on health is one of the least understood concepts in medicine.

On the other side of this coin is the rise of ‘wellness’. This surging trend has ushered in a wave of enthusiasm for preventative self-care, but also propelled a cascade of misleading messaging, hyperbolic claims and a shift away from science. As we saw with the anti-vaccination movement that evolved from a discredited article in The Lancet, misinformation, compounded by confirmation bias, spreads faster and deeper than the truth. This means misguided choices and misspent money, both of which have the potential to compromise our health.

Everyone wants to hear the tactical. They would have me tell you what to do each day, which superfoods to eat and which supplements to take. So what’s causing me to go against the grain and urge you to cast a critical eye upon all the messages of ‘wellness’? To disregard the powerful marketing aimed at having you ‘boost’ your immunity? Some argue that ‘the science just hasn’t caught up yet’. But it never will. Because that’s just not how science works.

PLACEBO EFFECT

A placebo is anything that seems to be a ‘real’ medical treatment – but isn’t. It could be a pill, an injection or some other type of ‘fake’ treatment. What all placebos have in common is that they do not contain an active substance meant to affect health. They are used in clinical trials to determine the effectiveness of a new drug. Sometimes a person can have a response to a placebo, either positive or negative. For instance, the person’s symptoms may improve or they may have what appear to be side effects. These responses are known as the ‘placebo effect’. Your mind can be a powerful healing tool when given the chance. The idea that your brain can convince your body a fake treatment is the real thing and thus stimulate healing has been around for millennia. Now science has found that in the right circumstances, a placebo can be just as effective as traditional treatments.

I don’t want to focus on lamenting times gone by or chastising the latest superfood. Life has moved on, and our health is better in some ways than it was in past generations. But I can’t help but wonder if we have thrown the baby out with the bathwater? This book is not about quick fixes and cure-all remedies. For many, a mindset shift from sick-care to self-care means we’ve become more intentional about our diets, nutrition, exercise and lifestyle as they relate to health. As the evidence builds, conventional medicine can no longer afford to ignore its place either. It may be the best we have against the uncontrollable surge of NCDs that now plague our modern lives. Several scientific studies explored in the following chapters demonstrate that sustaining certain positive lifestyle choices lowers risk, and that those already diagnosed can have their treatment effectively reinforced by shifts in habits and the provision of strong support networks.

SOLVING THE PUZZLE OF BETTER HEALTH

Health, both physical and mental, starts and ends with your immune system – the guardian control centre behind all other body systems. Ultimately, the immune system seeks peace with the environment. Your goal is to create one that doesn’t require your immune system to lose its natural balance.

Like the brain, the immune system is a learning system. It evolved to anticipate inputs from our environment. We can no longer ignore the fact that our fast-paced, over-consuming, unrelenting lives distort these inputs and are slowly degrading the balance of this carefully crafted system. Despite the fact that our world has changed – or, more correctly, because of that – it’s more important than ever that we anchor ourselves to the things that came so intuitively to our ancestors yet present the greatest challenge in our modern-day 24/7 culture. For example, a sensible lifestyle, getting enough sleep, exercising regularly, eating healthy foods and cultivating the mental bandwidth to adapt and self-manage the constant pressures of modern life. The future is not conventional medicine or alternative medicine – it’s a fusion of modern medicine with the intuitive tools of our great-grandparents.

For those of you who are curious about the forces within that can determine your wellbeing outside of your doctor’s realm, but are nervous to venture into the sphere of Dr Google and online influencer quackery and tired of being told to juice celery, this book makes no claims for quick-fix cures but will provide you with knowledge and direction. Understanding immunity can help you navigate the long game for health. Instead of boosting your immune system: support it. Honour its finely honed balance – one that is so essential to feeling healthy and living well. In the following chapters I will share my own personal tips and tricks, teaching you how to incorporate modern versions of ancient traditions into daily life. Think of these as lifestyle tweaks and changes backed by science. This is in no way prescriptive, nor a magic bullet to health. Quite simply, it is a gentle nudge in a better direction.

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