Defending Against the Greatest Killer

From Lifestyle is the Best Medicine podcast notes for episode 1, season 1.

The Greatest Killer

An estimated 100 billion people have died throughout the world’s history. It has long been the quest of many to find the fountain of youth, or the secret to immortality. But to find that secret, you must know the most common causes of death.

Take a guess: What has been the leading cause of death throughout all history? Is it war? Birth complications? Poor nutrition? Heart disease? Cancer?

In this, the first season of the Lifestyle is the Best Medicine Podcast, we will talk about just that: the greatest killer ever, the thing that has caused over 95% of all deaths and the secrets to how we defend ourselves against it.

We often measure the severity of something that causes death by looking at mortality rate. If we look at what has had the highest mortality rate throughout history, we see that:

  • The Plague killed over 1/2 of the European population in under a decade.

  • Within a century of Columbus arriving to the Americas, it wasn’t war that killed the most of the native people on the American continent, it was infectious disease. In some instances, 90% of community populations were decimated by smallpox within a matter of just a few short years.

  • AIDS has killed 35 million people.

  • The influenza pandemic of 1918 killed up to 100 million, with most of the victims dying in less than 6 months.

  • To this day, it is still the case that respiratory infections and diarrheal diseases are the top 2 killers of people in low income countries.

The clear winner is infectious diseases. From Malaria to tuberculosis to influenza, HIV, measles, smallpox, cholera, typhoid, and the list goes on and on and on. It is unequivocal that infectious disease is the grand champion of killers.

In today’s episode we are talking about: The immune system…what it is, how it works, and how it protects us from disease. Throughout the rest of season 1 we’ll be discussing how to optimize the immune system with a focus of course being on what we can DO to help keep it strong. This is a very appropriate discussion to be having right now as we are in the middle of the COVID-19 pandemic. Much of what we talk about will help provide a better understanding so you can be better informed as you try to navigate some of the confusion around it.

But even outside of the current pandemic, the things we’ll be talking about are universally important. After all, infectious disease has been the leading killer up until we discovered that germs (pathogens) could be spread and all the subsequent discoveries on how to protect ourselves.

So let’s rewind a bit and look back to how we got to what we know today.

The Greek Physician Hippocrates … who died in the 4th century BC … that said, the ”Natural forces within us are the true healers of disease.” Prior to him, it was believed that disease was caused by superstition, or the gods. He was the first to separate medicine from religion and he believed that disease was not a punishment inflicted by the gods, but rather the product of things like environmental factors, diet, and living habits. Have you ever heard that from your doctor??? Yes, he was handing out the same advice over 2400 years ago. This is part of the reason why we call him the father of modern medicine.

Fast forward more than 2000 years. There have been many infectious disease epidemics. One particularly lethal virus was smallpox. During the 18th century, over 400,000 Europeans were killed by smallpox and its complications every year. Yes…EVERY YEAR. Over 80% of children that contracted it died. This was a very deadly virus. When exposed to it from the European colonizers, up to 90% of the Inca population was killed by it in just a matter of years. So towards the end of the 1700s, an English physician named Edward Jenner made an interesting observation. He realized that milkmaids did not contract smallpox. He thought this might be due to their exposure to the similar, but less dangerous disease cowpox. Cowpox was a mild disease that would spread from open sores on cows to the dairy workers. They too would get these pustules on their hands and it would spread to other parts of their body. He performed history’s first “vaccination” when took some material from a cowpox scab and injected it into an 8 year old boy…who was then protected from smallpox.

But there was still a missing piece of the puzzle - how was smallpox transmitted from person-to-person? It wasn’t until the 1850s that scientists discovered microscopic organisms in body fluids of people with disease. Before the discoveries of this time, it was thought that “bad air” or a poisonous vapor filled with particles from decomposed matter is what caused disease. But with the discovery of these microscopic organisms, the Germ Theory of Disease was presented and is still accepted today.

It was during this time that things like boiling water was adopted as a health practice, and it was British nurse Florence Nightingale, the founder of modern nursing who wrote in 1860 “Every nurse ought to be careful to wash her hands very frequently during the day.”

Why do we have an immune system?

Since the 1850s we have learned much about germs and how we can protect ourselves from them, and how our body defends itself from them. And that’s where we come to the immune system.

So let’s start with the why…why do we have an immune system?

The easy answer: It’s our body’s biological defense system. It helps protect us from disease causing threats to the body.

We typically think of the immune system as protecting us from germs (what we call pathogens)… most commonly bacteria and viruses, but it’s not just germs that it protects us from. We use the phrase…“it protects self from non-self”. What we mean by that is that immune system cells are always on the look out for any foreign material. The immune system protects the body not only from bacteria and viruses, but also from harmful substances and cell changes within the body…which we will discuss in more depth in later episodes.

What is the immune system?

So the immune system is our defense against pathogens.Pathogens are disease-causing germs such as: 

  1. Bacteria

  2. Viruses

  3. Fungus

  4. Parasites

How do pathogens spread?

Direct contact

  • With infected skin, mucous membranes, or body fluids. (Think cold sores - from the herpes virus, or AIDS - from HIV)

Indirect contact

  • When an infected person touches a surface, like a doorknob or faucet handle and leaves behind microbes that are then transferred to another person who touches the surface.

  • Droplets spread by sneezing, coughing, talking or even just breathing and then transmitted to another persons mucous membranes.

Common transmission methods

Common vehicles:

  • Contaminated food, water, blood, body fluid (think E. coli and Salmonella)


  • Creatures such as fleas, mites, ticks (think malaria, West Nile virus, yellow fever)

Airborne transmission:

  • Droplets or dust particles containing microorganisms suspended in air (think tuberculosis, measles, hantavirus, COVID-19)

How do pathogens enter our bodies?

  • Eyes

  • Mouth

  • Nose

  • Urogenital openings

  • Wounds or breaches in the skin barrier (mosquito bite)

How does the immune system protect us?

First we have physical barriers:

  • skin - covers outer surfaces

  • mucous membranes - covers inner surfaces

Several things support this protective wall:

  • Enzymes in saliva, airways, and tear fluid can destroy cell walls of bacteria.

  • Many pathogens that are breathed in get stuck to mucus in the airways and moved out of the airways by little hair-like structures called cilia.

  • Stomach acid can kill most pathogens that enter with eating or drinking.

  • Normal flora - harmless bacteria that reside on the skin, mucous membranes, and in the gut can protect by competing for attachment sites and essential nutrients, or by excreting substances that inhibit or kill pathogenic substances.

  • Coughing and sneezing are reflexes that help remove pathogens.

And if a pathogen gets by these initial defense systems then a system of organs and cells will play defensive and even offensive roles in ridding the body of the pathogen:

The primary lymphoid organs produce defense cells called lymphocytes. These are:

  • The bone marrow - produces these lymphocytes

  • The thymus - a gland just higher the heart and behind the central sternum mature and differentiate these lymphocytes into cells that are capable of recognizing “non-self” proteins…or what we call “antigens”.

* During the course of life, both of these organs will gradually turn into fat tissue - which we will talk about in a subsequent episode about the effects of aging on the immune system.

The secondary lymphoid organs are where these defense cells do the work.

  • Lymph nodes - the lymphatic system is continually exchanging substances between the blood and tissue in the body. The fluid that isn’t taken back into the blood system in drained through lymph vessels, and filtered in lymph nodes on its way back to the superior vena cava, (a large vein that enters the heart) to re-enter the blood system. These “filter stations” contain many defense cells, which will trap pathogens and activate the production of specific antibodies in the blood - this is why when you are sick, your lymph nodes can become swollen, painful, or hard - it’s a sign of an active defensive reaction.

  • Other lymphatic tissue - Near areas where pathogens can enter the body through mucous membranes (like airways or the urinary tract) lymphatic tissue can be found beneath the membrane to help prevent pathogens from attaching and spreading.

  • Spleen - part of its job is to store and release defense cells when needed.

  • Tonsils - due to their position in the throat, defense cells stored here come into contact with pathogens especially soon and can activate the immune system immediately. Adenoids are part of the lymphatic system, and there is other lymphatic tissue in the throat region (that takes on the function if removed).

  • GI tract:

  • Small bowel/appendix - more than half of all the cells that produce antibodies are found in the bowel wall. Antibodies are protein molecules that recognize non-self substances, mark them, and destroy them. They also store information on these foreign pathogens to be able to react quicker next time.

  • Large bowel - contains bacteria (normal flora) that make it difficult for other pathogens to settle and enter the body.

Putting it all together

A pathogen lives in another host. Let’s pick an example. And since we’re in the middle of a global pandemic, we’ll choose the virus that causes COVID-19, or the SARS- CoV-2. (Now a little disclaimer, the information we have on this is changing, we’ve only know about this virus for a matter of months. That’s not a lot of time for science to figure everything out. In fact in 2014, almost 100 years after one of the deadliest viral pandemics, we were still getting new theories on how the 1918 influenza started. So we’re really early in this process. So in today’s example, we’re talking about something that in a year from now might be different….but this is just for illustrative purposes to help you understand how the immune system responds to pathogens.)

So back to the example. It starts in a host. (we still don’t know for sure the original source and it’s not the purpose of this show to speculate, but somehow the virus enters a host.)

As it enters the host, the body recognizes the virus as foreign — The immune system gets activated by things it does not recognize as its own (antigens - proteins on the surfaces of things like bacteria or viruses.) When antigens attach to special receptors on immune system cells, a whole series of processes are triggered in the body.

Innate response (Non-specific) Provides a general defense against harmful germs and substances 

  • Mostly fights using immune cells that will “kill” or “eat” harmful cells or substances

Adaptive response (Specific) Once the body comes into contact with a disease-causing germ for the first time, it can store that information (It it can be efficient) so the next time it comes into contact with it, it can act quicker.

  • This is why with some germs, you’ll only get sick the first time you come in contact with them (chicken pox)

  • As part of the response, some of the defense cells will makes antibodies and use them to fight germs it now recognizes. These antibodies are specific to this virus. It’s part of the good thing about the immune system- it helps it “remember” what to do when it is exposed to the pathogen again. It’s also part of the bad thing about it…if the virus mutates, or we get exposed to a different one, the antibodies won’t recognize and you’re basically starting over every time you get exposed to a new virus.

Autoimmune response Aside from the innate (non-specific) and the adaptive responses, you can also get what we call an autoimmune response, where the immune response is activated by the body’s own cells. This is not caused by a pathogen, but the body’s own cells have proteins on their surface, too…and these proteins don’t usually trigger the immune system to fight the cells, but sometimes the immune system mistakenly thinks that the body's own cells are foreign cells. It then attacks healthy, harmless cells in the body.

How do we get sick?

So the virus is now reproducing in the host (us) … in the ideal situation the body mounts a response. We are all exposed to thousands of viruses everyday. They are everywhere. Most don’t make us “sick”. Most of those are denied entry to our system by the body’s initial defenses.

Infection occurs when the pathogen enters the body and begins to multiply. In our example of COVID-19, the virus likely binds to cells in the nasal cavity and starts replicating. As the virus becomes more prevalent, it migrates down the respiratory tract - where a more robust innate (general) immune response is triggered. For most of the infected people, the disease is restricted to the upper airways.

For those that are unable to defeat the virus at this point, the virus gets deeper into the lungs at the cellular level…all the way to the alveoli (where oxygen is transferred into the bloodstream). As the virus reproduces in these lung cells, a toxin destroys the lung cells…and in response to that, the body tries to repair the damaged cells, but it can leave severe scarring. When you destroy the breathing cells in the lungs and then as they try to repair you are leaving scar tissue, you end up not being able to get oxygen into the blood and THIS is how it gets dangerous - people aren’t able to get enough oxygen.

So it’s actually the immune response, the healing response that can cause the most damage in pathogens like this.

Most of the symptoms you experience are due to the immune system response. The bigger the response, the more severe the symptoms. Sickness doesn’t happen in everyone that’s exposed or infected. By sickness we mean symptoms. Not everyone who gets infected gets sick. Sickness only occurs when the pathogen advances enough that the cells in your body are damaged enough, or if your immune system is responding enough.

Let’s look at the common symptoms:

  • Fever is a common immune response. Fever is not caused by the virus, it’s caused by the body responding to the pathogen. Heat inactivates many viruses, so by heating our body up, we’re fighting the pathogen. Now I say this with caution…because some use this type of information to not treat the fever and just “let it ride out”. While in some cases, there is evidence that not treating the fever can help fight the infection, the danger lies in the fever itself. The increase in body temperature can itself cause destruction of body cells, changes in blood flow to different body organs, or harm to the gut, the kidneys, the brain, the liver, your blood system or the cardiovascular system. SO, THIS IS WHY YOU SHOULD MAKES DECISIONS ON WHAT TO DO WITH A FEVER WITH YOUR PERSONAL PHYSICIAN. They can be dangerous, especially in children.

  • Not only does the immune response cause fever, but the some of the chemicals that are released in response to the virus will cause the symptoms of muscle aches, joint pain, fatigue, sore throat, painful and swollen glands.

The immune response is an inflammatory response - the symptoms you feel are caused by this inflammatory response. That’s why anti-inflammatories are commonly taken to relieve the symptoms. In the case of COVID-19, the “disease” is the “illness or collection of symptoms” that are caused be the SARS-COV-2 virus.

The irony here is that to rid yourself of the pathogen, you have to mount an immune response. But that immune response is actually what can be making you feel sick, and in some cases kill you.

What determines if it kills you? If you can get rid of the virus before you’ve suffered enough damage to kill you then you’ll survive. If your defense system is overrun, it can become quite serious. For most pathogens the immune system will do its job and you’ll survive, likely with an increased ability to fight another infection.

There are a few scenarios that exist that will lead to more serious illness:

A weakened immune system - people who have weakened or suppressed immune systems. If you can’t fight the pathogen, it can eventually do enough damage and overcome you.

Aggressive germs

With some pathogens, we just don’t mount an immune response. Just as we have evolved to defend against pathogens, pathogens have evolved to evade these defense mechanisms. (for example: there are 84 known types of Streptococcus pneumonia, an important cause of bacterial pneumonia - each type has a different structure of antigen (surface markers) so our immune system has to recognize each type - this is how the same pathogen can cause disease many times in the same individual

In the case of the Influenza virus - if surface proteins mutate they won’t be recognized by existing antibodies - this means the body has to start from scratch in its immune response to each new variant. You have different types, then different subtypes, within the subtypes you have groups, and even subgroups.

For the virus that causes COVID-19, it’s not the only known Coronavirus. Coronavirus is a family of viruses. We call them “Corona” viruses because they have “crown” (corona is latin for crown) -like spikes on their surface. We don’t pay attention to them because they typically only cause mild symptoms like a runny nose or coughing (common cold). If you remember in 2002-2003, there was an outbreak of another Coronavirus - SARS-CoV, it caused the illness we call “SARS” an acronym for Sever Acute Respiratory Syndrome. The illness COVID-19 is caused by the SARS-CoV-2 virus. SARS was much more deadly in terms of death rate - (it killed a higher percentage of people who got it). But less than 1000 people died from it. So why if it’s more deadly is COVID-19 killing more people? Even though it has a lower death “rate”, it is more easily transmitted. We think that’s because in COVID-19 that highest viral load is in the nose and throat of people early on (which means it’s more likely to be transmitted by people without symptoms vs. in SARS, the highest viral load peaks much later in the disease process, so people develop worse symptoms before they become the most contagious.

Some viruses will enter “latency”, where the virus is not being replicated and does not cause disease, but can be reactivated and result in recurrent illness - this happens with viruses like Herpes and Epstein-Barr, the Herpes virus will remain in nerve tissue (where it is difficult to detected because there are few defense cells in nerve tissue. It will kind of just hide there. Once it reactivated, it then presents itself to the epithelial tissue…causes the common sores that we see with Herpes, and the immune response is again activated and fights it off, clears it from the epithelial tissue and it just hangs out in the nerve tissue until it gets activated again. This is also how we get Shingles. It’s caused by the same virus that causes chicken pox and it can reactivate after being dormant for years - showing up in the form of Shingles.

Another technique that some aggressive pathogens employ is to resist the effects of a normal immune response. Tuberculosis uses defense cells as their primary host. It reproduces in the defense cells themselves and can lie dormant and wait for activation at a later time.

Some pathogens actually suppress the immune system (this can make you more susceptible to secondary infections). Most don’t die from measles, but Measles induced immune suppression, which makes you susceptible to common bacterial infections. 10% of global mortality of children under 5, malnourished children are the main victims. We see this happen frequently and it’s why many suffering from a viral infection will actually get a pneumonia that is caused by a bacteria that will then be the cause of death.

AIDS is the most extreme case of immune suppression caused by HIV. With AIDS, there is a gradual loss of immune competence. As your immune system is weakened, eventually you’ll be exposed to a pathogen that you would likely have been able to fight off, but now that your immune system is weakened so much, you are much more susceptible to exposure to pathogens.

When we look at the things that can weaken the immune system, by now you can see that the entire system is very complex and it’s critical that it stay in balance. Not enough of an immune response and you get in trouble, too much of an immune response and you get in trouble.

There are many different ways the immune system can be weakened:

For most, the immune system regulates itself and doesn’t need much help. However in some people, medications or immune system disorders can cause overactivity or low activity.

  1. Primary disorders

  2. Secondary disorders

  3. Allergies and asthma

  4. Autoimmune disease

We’ll be talking more about some of these situations in episodes to come so we won’t go into too much detail at this point about them.

Of course the next question is - if the immune system can be weakened, can it be strengthened…or boosted?

Everyone at sometime has been told: “Take some Vitamin C to boost your immune system.” It’s a multi-billion dollar industry, so there’s clearly incentive for those to convince you that there are secrets to boosting your immune system.

But here’s the secret: while you can definitely “optimize” your immune system, you can’t “boost” it. There is no such thing as a boosted immune system. Now I say that and understand that it can be a relative term. There are definitely things you can do to prevent it from “weakening”, so in a sense if you have a weakened immune system, and you do things to remove those weaknesses, then some could argue that you are boosting a weakened system. But in most respects, you can take a normal immune system and then “boost” it. You can only optimize it, and what I mean by that is making sure you aren’t doing things that will weaken it. It’s all about preventing it from weakening.

What can we DO to optimize the immune system?

That’s where the rest of this season will take us. There is much too much to talk about in just a single episode. And because this is a podcast designed to emphasize how we can use lifestyle as focus on our health, we will always ask this: What can we DO?

Remember this if you don’t learn anything else today: Knowledge is not power, it only turns into power when we DO SOMETHING. Work over time is power.

Optimizing the immune system in a healthy way starts with things we can control. Talking about the things we can’t control doesn’t help us optimize our health. But everyone, no matter the capacity of your immune system, everyone can do things that will weaken it further, and everyone can do things to optimize what you’ve got.

So today, in the spirit of DOING something, choose one thing you can change, one thing you can do daily that helps you optimize your health. If you haven’t already, I’d suggest the first thing you do is to set aside some time and really analyze why you want to be healthy. Write it down, and write down your personal vision of health. Evidence has shown that to make lasting, sustained changes to your behavior, having some purpose will be one of the greatest motivating influences.

To help you with your Personal Vision Statement, we’ve created a worksheet that will assist you in creating it and using it to help you make the progress you desire. You can find that in the Meducos Library, where you’ll also find additional tools and information to help you on your path to achieving health.

Thank you so much again for joining us. Please like and subscribe to the podcast as it really helps us to reach more people just like you. And tune in to the rest of the season as we learn what actions we need to take to optimize the immune system in a balanced and healthy way.

And now that you are on your way to making lifestyle the best medicine in your life, go share what you’re learning with someone else and together we can #SpreadHealth. Until next time, have a happy and healthy week.

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