It is interesting that we inhabit a machine that is far more complex, sensitive, and fragile than a race car. Could you imagine owning a race car, driving it hard, and never really understanding it? At a deep level, that ignorance would affect the way you drive, the way you diagnose problems, and the way you use the machine.
With a race car you would understand that dirty fuel leaves deposits on the engine parts and fouls the engine. It is easy to picture grime and particles building up and causing all kinds of problems, so you would keep only the best fuel in the tank, and you would not make exceptions, because at a competitive level you know you cannot win running dirty fuel. You would also know that the engine, the transmission, the brakes, the fuel lines, the hydraulics, and the electrical system all have to be maintained, cleaned, and diagnosed on a schedule, and that when a part starts to fail you attend to it quickly.
So why don’t we think about the human body, which is our life support, the same way? Is it ignorance, is it that we take the body for granted, or does anxiety keep us too scattered to hold our attention on the details long enough to act? It is probably all of these things at once, and one more thing that gets overlooked. Our anxiety self controls the narratives we create in our mind. When we are chronically anxious, even when we are successful by every outside measure, we are running on the older, faster, threat detecting circuitry of the brain, and the reasoning centers get less of the signal. There is less logic in us, and more emotion and reaction.
The body is a singular machine, meaning there is nothing else like it, no other machine that builds itself, repairs itself, runs itself, and knows it is doing so. The big difference between the body and a car engine is that the body carries a psychological system that has to be maintained too, because when it is not, thought and mood start showing up in the tissue. And how could they not? The mind is also mechanical, chemical, and electrical, made of cells and neurons and tissue. The body and the mind are running on the same system. We will come back to that.
First, let’s look at the systems we have. There are the framework systems, the skeletal system and the muscular system, which give us structure and movement. There is the nervous system, which carries signal and control. Then there are the systems built out of organs working as a group, the digestive system, the circulatory system, the respiratory system, the endocrine system, the urinary system, the lymphatic and immune system, the reproductive system, and the skin, which is an organ system of its own.
Now let’s break the body down into smaller parts. The smallest parts inside the body are not the smallest things we know of in the universe. Quarks, the up quark and the down quark, bind together to form protons and neutrons. Protons and neutrons form the nucleus of the atom, and electrons, which as far as we know are not made of anything smaller, complete it. An atom of a single kind is an element. Atoms bond with one another to form molecules. Molecules build the structures inside the cells of the body, and cells cluster together to form tissues. It is hard to believe, but your blood is a tissue. Tissues form the organs and the structures built from them, bone, muscle, nerve, skin, and hair. The organs are the real machinery of the body, but they operate through a network of systems, the nervous system, the respiratory system, the circulatory system, and the rest.
All of these systems are reliant on nutrition, the intake of food and water that supplies the replacement elements and compounds we use to build and rebuild, and the energy for movement and every other biological process.
There are two primary categories of what you can put into the body. The first is nutrients, the things the body needs to build, repair, and run itself. The second is toxins, compounds the body has to break down and carry out through the waste systems. Alcohol is the clearest example of the second. It carries seven calories per gram, so it is not nothing, but it delivers no vitamins, no minerals, no amino acids, and no essential fats, and the body treats it as a poison and drops everything else to clear it. Then there is a third category, and it may be as important as the first two. There are substances we do not digest or absorb ourselves at all, the fibers and the resistant starches, which pass through and feed the friendly bacteria living in the colon. We are not the ones being fed. They are. In return they produce short chain fatty acids that nourish the lining of the gut, they crowd out organisms we do not want, and they influence immunity and mood. We eat for them as much as we eat for ourselves.
There are three groups of nutrients. The first are the macronutrients, which we need in large amounts, carbohydrate, protein, and fat. In a whole food diet, carbohydrate is usually the largest share by weight, then protein, then fat. The body can manufacture some of this material on its own, it can build fat and it can make glucose out of other raw material, but it cannot make the essential amino acids or the essential fatty acids, and those have to come in through food.
Water sits in a category of its own because it is not a fuel and not a building material, it yields no calories and passes through none of the pathways that break carbohydrate, protein, and fat down into energy. It is the medium instead, the solvent every reaction runs in, the transport that carries nutrients in and waste out, the coolant that holds our temperature, which is why we require more of it than anything else and die without it in days.
The second group are the micronutrients, the compounds we need in much smaller amounts, the vitamins and the minerals. The minerals include sodium, chloride, potassium, magnesium, calcium, iron, and zinc. Table salt is a compound of two of them, sodium and chloride. Interestingly enough, we produce a few of these ourselves. We make vitamin D in the skin with sunlight, the bacteria in our gut make some vitamin K and some of the B vitamins, and we can convert the amino acid tryptophan into niacin. Most of them, though, we have to eat.
The third group is more abstract in terms of exact benefits. We know we need these compounds, but they do not quite classify as micronutrients. These are the phytochemicals and the antioxidants, families like the polyphenols and the flavonoids. Plants build these compounds themselves, using energy from sunlight, often as a defense against stress such as ultraviolet light, insects, and drought. In us they appear to affect how well our cells hold up and how well we fight off disease.