Fluid Intelligence: The Immune System

Part 1. Germs, Sewers and Vaccines

In the 1800s microbiologist Robert Koch’s discovery of 'germ theory' changed how we viewed disease and set the foundation for modern medicine. The previously held belief that infectious diseases such as fevers, agues, poxes and plagues were caused by 'miasmas' or imbalances in the body's 'humors', was overturned. We now knew that infectious diseases were the result of the spread of micro-organisms like bacteria and viruses.

For as long as people have been living together in groups we have understood the need for basic sanitation measures. There is a case to be made that a lot of the rules contained in religious texts were really just public health measures designed to prevent the spread of disease (including the sexually transmitted variety). Still, germ theory finally gave us a mechanism to explain how infectious diseases spread. It also set in motion the development of mass sanitation measures - water systems, sewers and the like - which have been the single most effective health measure in human history. The second most effective measure, the development of vaccinations, also stems from our understanding of microorganisms; as does the third, the mass production of antibiotics. It is also worth mentioning the more recent success of anti-retrovirals in treating HIV. Though still not as widely available as needed, in countries like the UK these have turned what was a terrifying diagnosis into a well-managed health risk, in what is very much an unsung medical success story.

Sanitation and vaccination have vastly improved human life expectancy and reduced infant mortality and disability. Despite this, in the past few decades we have seen a backlash against vaccinations, despite overwhelming evidence as to their safety and efficacy. (Interestingly, we have not seen a similar backlash against the necessity for mass sanitation). Antibiotics continue to be the mainstay of treatment for bacterial infections, though the evolution of antibiotic-resistant strains of bacteria is set to become a significant issue. The covid-19 pandemic has also been a sobering reminder of the threat of infection and epidemic. In short, we are not out of the woods when it comes to infectious disease yet.

Despite this the undeniable trend of disease in the 'developed' world over the past half-century has been towards non-communicable - i.e. non-infectious - illness, such as cardiovascular and metabolic diseases like heart disease, type 2 diabetes, respiratory conditions and certain cancers. A significant burden of disease in the modern world, including mental disease, is now largely the result of social, economic and lifestyle factors, not infection. We might ask what role our immune system, which evolved primarily to fight off infection, has in this new world.

But does our immune system only deal with infections? In the human body, every 'system' usually does more than one thing (our skeletal system makes blood cells, our skin helps produce calcium, our kidneys regulate blood pressure, and so on) and the immune system is no exception. It is a holistic system, managing many different facets of health, including our mental health. As well as working as a kind of sixth sense - constantly monitoring the outer and inner world - it plays a crucial role in the healing, maintenance and repair of our bodies. We'll start by looking at one of the primary ways it does this.

Inflammation; Our Painful Friend

Inflammation is a ‘universal process' in the body, affecting all of its myriad parts and systems. It is also our body's way of telling our brain that something is wrong. To this end it affects everything from our appetite to our mood, and even how social we feel. It is a finely tuned system equipped with 'cascade mechanisms' to kick start it into action and feedback loops to slow it down when the job is done. Continually overstimulating this intricate system can lead to systemic inflammation, leading ultimately to chronic disease. A physical toxin can do this - tobacco smoke for example - but we now appreciate that mental stress can also push the body into a pro-inflammatory state.

Inflammation is an essential component of our immune system. Simply put, it creates the 'conditions' which allow the immune system to work. As any military strategist is aware, if the conditions of a conflict zone are not right - poor weather, hostile locals, impenetrable terrain - then any campaign is doomed from the start. Likewise the immune system needs the right conditions to fight off invading pathogens and repair damage. To this end inflammation 'prepares the ground', leading to the notorious five cardinal signs of inflammation: rubor, tumor, calor, dolor and functio laesa; respectively redness, swelling and warmth plus pain and loss of function. Basically, the first three result in increased blood flow to the affected area - to increase immune cell traffic - and the last two 'guard' the affected area.

Inflammation isn't always obvious however and, unlike with a bruised shin, we may not even be aware of these signs until it's quite late. You will doubtless have had times when you've felt rotten - irritable, tired, anti-social - for no obvious reason only to come down with a cold a week later. In all likelihood you caught the cold a while back and your body was busy undergoing an inflammatory cascade just beneath the radar of awareness. Indeed, one of the reasons coronavirus was able to spread so widely was the lag between people getting infected and showing symptoms around 10-14 days later. Hence the value of being able to 'listen to your body', often easier said than done.

Yet, not all inflammation is a response to infection or injury. During the night our body goes into a pro-inflammatory state anyway in order to promote healing. This explains why people with any kind of infection - especially children - tend to have higher fevers during the night. Inflammation also accounts for why people with any kind of injury or arthritis tend to feel stiff in the morning and why, if one has been doing a lot of physical work, waking up in the middle of the night can be so uncomfortable.

To better understand inflammation it is useful to get an idea of how the immune system works as a whole. I often visualize the immune system as a kind of military system. This isn't entirely fanciful as its basic aim is to protect the body from invading pathogens and remove 'non-self cellular matter' or, like an engineering corps, to repair damage. This 'immune army' has two major branches: the innate and the adaptive systems.

Innate Immunity: Self and Non-Self

The innate immune system is the first line of defence. It includes the barriers of the skin, mucous membranes and the gut as well as such tricks as turning up the heat - fever - to kill off invading microorganisms. The innate system has legions of deadly cells to assist in its work. These cells are trained in the thymus gland, which sits behind the sternum, and also to a considerable extent in the gut, and in these training grounds they learn the essential art of distinguishing friend from enemy, to learn the difference between self cells (don't attack) and foreign proteins (attack). It's an unforgiving training camp; immune cells which pass the test and attack foreign pathogens go on to the next stage, but those who attack 'self' are basically told to self-destruct (though not all do, and this is thought to be one of the processes by which auto-immune disease can start).

Having been thus trained they specialize into their various jobs - from the quick and dirty complement factors which basically punch holes in invading organisms, to the more sophisticated natural killer (NK) cells which lyse (i.e. destroy) virus-infected cells and then recruit other immune cells to the fight. The way they recruit and signal to other cells is via chemical messengers called cytokines. Other cells of the innate system include neutrophils, macrophages and dendritic cells (DCs). These are 'phagocytes', so called because they basically eat invading cells. Having eaten the invading cell they are promoted to the title of antigen presenting cells (APCs) and then migrate to the lymph nodes where they present antigens - i.e. bits of the invading cell - to 'naive' T cells. Here the T-cells 'learn about' the antigen and prepare for future encounters. These T cells are part of the second branch of the immune system, the adaptive system, and to continue the metaphor, they are akin to a sort of military intelligence.

Stress and Immunity

Before going into the adaptive system in more detail, there is something else worth noting about the innate immune system and this is its capacity to induce behavioral changes in us. Certain complex molecules used by the innate system, such as TNF-alpha, IFN-alpha or the aforementioned cytokines, are behind many of the experiences of being ill, which include not only the experience of fever and pain, but also fatigue, malaise and feeling down. Not only this, but the innate system also activates the hypothalamic-pituitary axis (HPA) which is an essential part of our stress response.

The HPA - a kind relay network between the hypothalamus deep in the brain, the pituitary gland just beneath it and the adrenal glands above the kidneys - regulates the release of cortisol which is a powerful anti-inflammatory. Cortisol dampens down the inflammatory effects of the immune system, especially during 'active times' such as after waking up. It also increases metabolism to make more energy available to fight disease, raising blood sugar levels, numbing pain and fighting fatigue. It is a finely tuned system, very effective for short-term stressful events, but when chronically stimulated it is responsible for many features of chronic disease and 'burnout'. Those raised sugar levels reduce our insulin sensitivity putting us at risk of metabolic and diabetic disease, and the fatigue and pain fighting-effects in time lead to numbness and an inability to properly rest or sleep. (The immune-boosting effects of short bursts of exercise or cold showers, as well more pleasant activities such as meditation, yoga and saunas, are likely due in large part to their ability to 'reset' this overstimulated stress response.)

Adaptive Immunity: A Second Brain?

The innate immune system is certainly sophisticated enough, but it more or less does the same thing over and over. The adaptive immune system on the other hand is able to actually accumulate knowledge. When we say that we are immune to something, we are talking about our adaptive system. It consists of cells called lymphocytes, which are created mainly in bone marrow and which spend most of their lives in the lymphatic system or on the walls of blood vessels. These lymphocytes include T-cell and B-cells. The adaptive system is different from the innate system in that it is able to learn about foreign pathogens and create memory, and in this sense has intelligence. Indeed, it is a telling coincidence that the lymphocytes in our body have the roughly the same mass as our brain.

It takes longer to take action against pathogens however, usually around 10-14 days, and works roughly by destroying invading 'non-self' organisms. This is done by a class of the T-cell we mentioned earlier, the 'cytotoxic' T'-lymphocyte (CTL). As we saw, the CTL is triggered into action by one of the antigen-presenting cells which, a little like in the films where they give a hunter dog a scrap of the fugitive's clothes to sniff-and-go-catch, shows a fragment of invading cell for the CTL to go and lyse (of course we are talking about millions of such cells, not just one).

The other T-cell which learns is the TH 'helper' cell. These TH cells produce cytokines which recruit yet more cells to fight infection. They are pro-inflammatory, leading to those features of inflammation mentioned earlier, including those behavioral changes - fatigue, lack of energy and so forth, sometimes called sickness behaviors. There are a few other types of T-cell, such as the T-regulator cells that 'down-modulate', that is to say, calm down or switch off the activity of CTL and TH cells so the immune system does not get carried away. It is worth noting that T-cells play a crucial role in identifying and eradicating neoplastic (cancer) cells. At any one time there will be -among the trillions of cells in our body - such neoplastic cells, though fortunately these are almost always being picked up and destroyed by our immune system.

Antibody Factories and Vaccines

The TH cells also direct the other cells of the adaptive immune system, the B-cells. These are essentially factories for producing antibodies. Any given foreign organism, once smashed up by the immune system, will yield fragments of proteins that can be used to identify similar cells in the future. Once introduced to the B-cell it will go on to produce countless numbers of these antibodies. Antibodies are basically molecular 'tags' that circulate in the blood, each one tailored to the particular type of antigen found on the surface of a bacteria and if encountered it will latch on to that organism (or virus-infected cell). This allows for a quicker and more targeted response - one less dependent on the innate immune system and therefore less inflammatory and less debilitating. By adulthood we have billions of such antibodies in our system.

In other words, the adaptive immune system is able to identify and destroy the invading pathogen before it has time to multiply enough to cause disease. Vaccines work in this way - they contain non-active fragments of pathogens which trick the immune system into producing the right antibodies to latch onto and destroy the organism if it does ever get into the body (The Vaccine Knowledge Project has a short animation which explains this well https://vk.ovg.ox.ac.uk/vk/how-do-vaccines-work).

The Battle Scene

The methods used by the adaptive immune system to combat infection are efficient and ingenious, and they often work together to do battle: invading cells or virally-infected cells may be bound together for instance, all the more easier to target and destroy; they may be made 'slippery' so they cannot attach to anything; they may be made 'tasty' so that phagocytes will chomp them up or they may just simply be lysed - their cell walls broken down and destroyed.

Of course sometimes the system malfunctions and produces antibodies against 'self-cells' such as the insulin-producing cells of the pancreas - a problem which leads to type 1 diabetes - or the anti-gliadin antibodies which target the gluten protein and can lead to coeliac disease. A more common issue is sensitivity where certain proteins on food or pollen, or industrial or motor vehicle particles, cause an overreaction - specifically the over-release of cytokines and histamines - normally on a barrier site such as the gut or skin (or airways as with asthma). There is no easy solution to this growing problem, though identifying as accurately as possible the trigger and trying to reduce exposure is the current mainstay of management. Even something as simple as rubbing Vaseline just inside the nostrils can help trap pollen before it gets in the sinuses!

Can We Control Immunity?

To recap then; we have an immune system which can be grouped into the innate and the adaptive. Both systems work together. The innate system includes the barriers of the skin, gut and mucosa and uses inflammation to optimize conditions for getting rid of infection and repairing damage. It also presents bits of invading cells - antigens - to the adaptive system to 'learn from' and mount a more targeted response in future, with the help of millions of antibodies. Both systems use chemical messengers to feedback and regulate each other.

As well as affecting us physically the immune system also affects us emotionally and changes our behavior. Often this effect is subtle - we hardly notice it beneath the often relentless pace of our day-to-day activity or our ever-busy minds - but it is there and sometimes will make itself felt in dramatic and unexpected ways, which I'll talk more about in the next part, where we'll also explore questions such as; what conscious control do we have over our immune system; what can we do to strengthen our immune system, and why do I always get a cold when I go on holiday?

Part 2. The Waterfall

The year was 1910 and in Japan a young man called Tempu Nakamura was facing his own death. It was not the first time. As a spy working covertly for the Japanese military in Manchuria (a couple of decades before the brutal Japanese occupation), he'd been shot, starved and miraculously saved from a Russian firing squad by his comrades. He'd dished out his share of death too - putting his samurai sword to use against marauding bandits for instance, and delivering bloody vengeance on Russian soldiers who had themselves murdered three Japanese geishas some days before. These were not gentle times. But on his return to Japan he faced a more insidious and intractable enemy: tuberculosis, or TB. At the time there was no cure for TB and a gloomy Nakamura - previously a fit martial artist - resigned himself to a premature, cough-racked death. Fate intervened however, in the form of an Indian sage called Kariappa who he met one day in a waiting room and who, in a somewhat cinematic turn of events, invited Nakamura to study with him in the mountains of Nepal. Racked by coughs and fatigue, Nakamura nevertheless made his way to the verdant foothills for a two year stay.

This was no luxury retreat. In the morning mist he would join a handful of other pupils and sit up to his chest in a freezing stream for an hour. After, under the sage's goading, he would hike up a mountain to a waterfall, next to which he would spend the rest of the day meditating. As the months passed Nakamura began to change. The morning dips in the icy mountain stream, once torture, began to feel calming and even pleasant. After many weeks spent meditating by the waterfall his mind began to clear. His coughs subsided, his fatigue lifted and his mood improved. After many months of this he realized that his symptoms had vanished and he had never felt so strong. The spectre of death had vanished.

Yet, without regular practice not even enlightenment lasts and, after bidding farewell to his mentor, Nakamura returned to Japan whereupon he promptly lapsed back into his bad old ways - namely smoking, gambling and idleness. Before long the malaise and the coughing crept back in. However this time he knew what was needed - he was 'mentally immunized' you might say - and he soon resumed his meditation and cold water soaks, became a committed pacifist, and eventually went on to develop a kind of Japanese yoga system called shin shin toitso do (loosely translated as 'mind-body harmonization') which is still practiced to this day. His tuberculosis disappeared for good this time, and he went on to live a long and fruitful life.

Boosting Immunity

Many aspects of Nakamura's story seem fantastical, though they are backed by the record. Yet, one has to ask: how valid is his tale of 'curing' himself of an incurable disease? Granted, tuberculosis does not kill everybody who gets it, but Nakamura certainly seemed to be one of the unlucky ones: before his trip to India he was losing weight rapidly, sweating profusely at night, and coughing up blood; all of which indicate that the 'bacterial load' of TB had overwhelmed his immune system and was destroying his lungs. However, in the days before antibiotics he was somehow able to reverse this process. He was able to boost his immune system enough that it would contain the infection and later it seems, effectively 'clear it' from his body.

The question is how? What mechanisms might explain this recovery? What role does mental attitude play in the recovery of the body? We tend to overlook this aspect, particularly in our 'biomedical' approach to medicine. We might not say so explicitly, but so much of modern medicine is based on the assumption that the mind does one thing and the body another. Sure, we know that mental attitudes play some role in physical well being. Positive, optimistic mind states are associated with better outcomes for many diseases. But the how remains somewhat vague. Is it chemical, hormonal, neurological? Our mental processes and beliefs interact with our bodies in an elusive zone, but it is here that our immune system operates.

Immunity and the Brain

In normal conditions the brain is protected from the immune system by the blood-brain barrier (BBB). In cases of quite advanced infection - such as meningitis - this barrier is leaky enough that microorganisms can cross it, though normally it remains strictly closed off to such pathogens. In fact the BBB is even impenetrable to the body's regular immune cells and depends upon its own class of cells called microglia. These microglia are able to identify damaged or diseased nerve cells, using phagocytes (cell eaters) to limit any damage and clear up. Like any complex system the brain's immune system can become dysfunctional and is implicated in such conditions such as multiple sclerosis and Alzheimer's disease, and even depression.

The immune-inflammatory response has even been put forward as a mechanism by which vaccinations might lead to autism - the theory being that the immune-inflammatory response to the vaccine causes neuronal damage. However, and this point needs to be stressed, there is no established link connecting the two, and I would encourage the reader to look at the Immunization Safety Review: Vaccines and Autism (2004) (available on www.nationalacademies.org) for reassurance on this matter.

Inflammation can cause damage. While necessary in the short term for clearing infection, repair and healing, in the long term it impairs the functioning of the various cells, organs and systems of the body. It can cause microscopic scarring to tissue and damage to cells. We now also know that inflammatory molecules known as cytokines can cross the BBB, and therefore affect the central nervous system. The brain also produces cytokines in response to any kind of 'insult' - infections, trauma, stress, toxins and so on. In this way the immune system directly influences our behavior - making us feel fatigued, anti-social etc. - the aforementioned 'sickness behaviors'. So we can see how the immune-inflammatory system affects our state of mind. The question is whether our state of mind can influence it.

Holiday Cold

To approach this question we can look at a more familiar one: Why do I get a cold when I go on holiday? Most of us have experienced this. We’ve been working hard, looking forward to a break but when it finally comes it is sullied by a runny nose, sore throat and other flu-like symptoms. How come? One explanation brings us back to our hypothalamic-pituitary axis (HPA). You’ll recall that when the immune system kicks into action the hypothalamus in the brain tells the pituitary gland to stimulate the adrenals above the kidneys into producing cortisol. Cortisol is a powerful anti-inflammatory and limits collateral damage from the inflammatory cascade.

Psychological stress also activates the HPA. This makes sense from an evolutionary perspective: there will be times when we can’t be laid up in bed and will need to ‘power through’, and in such circumstances the body will tip towards an ‘anti-inflammatory’ state. The cortisol will raise blood sugar, increase metabolism and dampen down pain. Accordingly, once the 'stressor' is removed – e.g. work, escaping a hostile tribe – and the 'holiday' commences there is a rebound effect whereby the HPA winds down, the cortisol dries up and that inflammation which was being kept in check now runs riot; hence the ‘fluey’ symptoms.

The immune system is directed by the brain in other ways. The autonomic nervous system responds directly to stress. You will have heard of the ‘fight-flight-freeze’ response initiated by the sympathetic system and the ‘rest and digest’ counter-response of the parasympathetic system. These systems use chemicals such as adrenaline and acetylcholine to speed up and slow down the heart, for instance. What is perhaps less well known is that the autonomic nervous system also directly innervates the immune system sending nerves to, for instance, the thymus gland, the gut, mucous membranes, bone marrow and blood vessels.

We now begin to see how our mental state can directly affect our immune system, especially stress. Broadly speaking, stress inhibits our immune response. Sometimes this is necessary but in the long term it impairs our ability to fight infection or even malignant cells. Moreover chronic over-stimulation disorientates the feedback loops of the immune response. This imbalance can result in distressing and otherwise unexplained symptoms such as inflamed sinuses or gut pain, or 'psychosomatic' experiences like fatigue, depression or social avoidance, which can happen in the absence of any obvious pathogen.

The Loop Hypothesis

The 'loop hypothesis' is a model which aims to explain why, in certain circumstances, we experience disease - sometimes in the absence of an identifiable cause. It goes something like this: Most systems in the human body operate through feedback loops, and it is disruption of these loops which can lead to chronic problems. We can, however, re-train ourselves so that these loops can be restored and therefore return the organism (i.e. us) to a state of well-being.

As we saw in Part 1, the immune system works through a series of feedback loops. A pathogen gets into our body and starts to multiply. The innate immune system kick-starts into action to combat the infection. If we're lucky we will also have anti-bodies to this infection which will be latching on to the bacteria or virally-infected cells and marking them for destruction, so that they can be cleared before they reach a significant number. However the immune system will also be releasing chemicals to slow itself down so that it does not cause too much damage. As the infection is cleared, these 'calming' signals increase until the system returns to a state of rest. The autonomic nervous system - with nerves running directly to immune tissue - is also coordinating the immune response.

Ideally this system works in concert. However because this same system is integrated by our nervous system, that same nervous system can cause problems. If for example we are perceiving a continual threat - if our stress response is being triggered by anything from unpaid bills to a hostile colleague at work - then the immune loop is being prevented from closing. Are there ways we can voluntarily ‘reset’ our immune system and thus close the loop?

Take a Dip...

Nakamura was convinced that his cold stream meditations helped him overcome TB. Several studies now demonstrate an immunological benefit to cold water immersion (CWI) with one study in the Netherlands showing that participants randomly assigned to cold water showers (of no more than 90 seconds!) suffered less from cold-symptoms and were less likely to take time off work due to illness. Other research demonstrates that cold water exposure increases the quantity of certain immune cells.

How exposure to cold water enhances the immune system is still a matter of some speculation. We know that having a brief plunge into a cold pool or shower boosts blood flow to the skin and we know that our blood vessels are lined with immune cells so it's possible that cold water mobilizes the immune system in this manner. Another mechanism is that cold water immersion is an acute stressful event: It places us under a state of brief but controlled stress. Once over, one retires to a warm place, gets wrapped up and enjoys a hot drink. The 'burst' of stress is much more intense than chronic, insidious stress, but precisely because of this it is able to trigger the immune system into winding down. Of course, exposure to heat may be a more pleasant way to trigger the same homeostatic mechanisms - saunas and steam-rooms doing much the same thing as cold showers and plunge pools. In either case there is a benefit to exposing our bodies to cold and heat outside our chronic room-temperature zone.

...Break a Sweat…

It is now well established that physical activity has profound immune-boosting and anti-inflammatory effects. With exercise, the sympathetic nervous system kick starts into action; blood is pumped to muscles, airways expand, and an array of chemicals are released (for example the cytokine IL-6 from contracting skeletal muscle, which is pro-inflammatory but which in turn activates the anti-inflammatory IL-10 molecule in a classic feedback loop. The anti-inflammatory cortisol is also released during exercise). In many ways this mimics the stress of an acute infection, but again it stops after a relatively short time, the feedback loops close and the body returns to homeostasis.

Exercise is also important in recovery. 'Post-infection malaise' is a very common phenomenon whereby the infection is more or less gone, but we nevertheless feel exhausted and even depressed for weeks after. This can partly be explained by the fact that the immune system makes significant demands on the body's energy supplies. Another explanation comes from the central governor theory which proposes that our nervous system has a kind of internal dial which tells us how much energy we have to spare. In the case of an infection this 'governor' will tell us to conserve energy, leading to the experience of fatigue. This stops us from squandering precious energy and helps us recover.

However, as we have seen, sometimes this governor does not quite return to normal after the 'insult' but rather stays on high alert. It becomes sensitised. Sometimes this goes on for weeks, and sometime the fatigue becomes chronic, lasting years. Here again it is likely that brief controlled bursts of exertion would be effective in 'resetting' the default network to a higher threshold - in other words telling it that the body is capable of far more than it currently 'feels' it is.

A final note on physical activity is that it ‘mechanically’ helps the immune system in that immune cells such as CTL and TH cells patrol the blood vessels and the lymphatic system of the body, always on the prowl for potential invaders. One of the benefits of physical activity such as exercise, stretching, massage or yoga, is that it helps the flow of the lymphatic system (which, unlike blood, does not have a pump of its own) by squeezing and pumping.

...And Relax

What about meditation? Research into this field has surged in the past decade, and although not conclusive, the findings so far are promising. A recent review of around 20 randomized controlled trials found reproducible evidence that meditation reduces inflammatory markers, increases CD4 (regulatory t-cell) activity and also increased telomerase activity (which has a protective effect on cells during division and thus reduces 'biological aging'). In any case regular meditation practice reduces psychological stress and allows the body to return to a state of rest, or 'optimal functioning' whereby the feedback loops are allowed to complete their processes unhindered by mental impulses. In the words of Nakamura 'since the body can only exist in the present that's where the mind should be too'.

Good Fat, Bad Fat and Anti-Fat

Finally, what about diet? What foods are inflammatory or anti-inflammatory? The evidence is mixed. Still, one thing we can say with confidence is that eating a large amount of food in one go does produce an inflammatory response from the body, so binge-eating is not a good long term plan. Sugar is also pro-inflammatory.

Another proven fact is that adipose tissue (especially visceral fat, that is, fat around the internal organs) is pro-inflammatory. Fat cells release inflammatory molecules, known as adipokines, as well as hormones such as oestrogen. Fat is not entirely bad. In healthy adipose tissue there is an abundance of anti-inflammatory immune cells such as M2 macrophages and CD4 T-regulatory cells. However in the absence of physical activity and too many calories this adipose tissue switches to 'bad', pro-inflammatory fat leading to a state of constant, low-grade systemic inflammation. Muscle on the other hand releases its anti-inflammatory molecules called myokines, in this respect making it a kind of 'anti-fat'.

Our Bacterial Garden

Not all bacteria is bad. Our body is stocked with micro-organisms that play an important role in our health - the billions of bacteria in our colon for instance which metabolize vitamin B12 for us - and their presence plays an important role in regulating our immunity. It's no coincidence that around 75% of the weight of the gut is composed of immune tissue. So what we eat is important, and foods rich in bacteria - probiotic yoghurts, fermented foods, raw food - probably introduce a lot of beneficial bacteria to our immune system. You could compare it to a garden; the more benign bacteria you have covering it, the less chance toxic bacteria have to flourish.

Stacking the Odds

One of the lessons from the Covid-19 pandemic is that sometimes there is no immediate cure, pill or injection. When the vaccine was rolled out it on 2020 it reduced death rates by 57%*, but for a long time our only options were to reduce our risk of exposure to the virus and optimize our immune systems so that we were more likely to be in that group of people whose symptoms are 'mild or minimal'. How well we cope with disease is often down to managing probabilities like this. Unfortunately the human brain is not very adept at assessing risk, especially to something that can’t be seen or only appreciated through statistics. Some people reacted to the pandemic with an abundance of caution, isolating themselves, others with outright denial, becoming boorish and careless. However most of us seemed to adopt a pragmatic approach, getting on with things and following the rules, as it seemed to be in all of our interests to do so (which is very different from blind obedience, in which people follow the rules despite it going against their interests).

We can also stack the odds in our favour by optimising our immunity. Even though much of it works beyond voluntary control, hopefully we can now appreciate that there are a lot of ways we can harness its inbuilt capacity, not just to fight off infections, but to promote healing, boost our energy levels and lighten our mood. Essentially this seems to involve re-acquainting ourselves with our Stone Age bodies - eating vitamin-rich foods, avoiding sugars, more daylight, more activity - including occasional bursts of intensity - and more exposure to cold and heat, while reducing exposure to chronic stress. Not all of us have a nearby waterfall to meditate next to, but even 10 minutes mindfulness practice a day can make a difference, and while stories like Nakamura’s are interesting, it is worth remembering that it is not the dramatic transformations that make a difference, but those small everyday changes that are within everybody’s power to make.**

- H James, May 2020

Sources:

- Heaven's Wind: The Life and Teachings of Nakamura Tempu - a Mind-Body Integration Pioneer, Steven Earle (2017)

- 'Multimorbidity' as the manifestation of network disturbances, Sturmberg J.P, et al, Journal of Evaluation in Clinical Practice, 23, (2016) - 'The key pathways to health result from the modulation of the neuroendocrine and autonomous nervous system regulatory feedback loops. Chronic overstimulation of these pathways is the main contribution to poor health...'

- The anti-inflammatory effects of exercise: mechanisms and implications for the prevention and treatment of disease, Gleeson M et al, Nature Reviews: Immunology, (2011)

- The effect of cold showering on health and work: A randomized control trial, Geert A.B et al, PLOS (2016)

- Mindfulness meditation and the immune system: a systematic review of randomized controlled trials, Black, D.S, Slavich G.M, Annals of the New York Academy of Sciences, (2016) 

- *https://www.who.int/europe/news/item/16-01-2024-covid-19-vaccinations-have-saved-more-than-1.4-million-lives-in-the-who-european-region--a-new-study-finds. On a personal note, I was working in hospital at the time of the vaccine roll out and we noticed a dramatic reduction in admissions almost overnight. Those who were admitted to hospital were generally unvaccinated younger people.

** The late Dr Michael Mosley was an authority on such matters: https://www.bbc.co.uk/programmes/articles/3y685wld5pw50SBfq1hHjwk/10-easy-ways-to-boost-your-health-and-wellbeing-during-your-working-day#:~:text=Breaking%20up%20the%20working%20day,response%20to%20stress%20and%20pain.