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How human are we exactly? And who is really in control? Each of us consists of about 10 trillion human cells, but we also have 100 trillion microbial cells in and on us. This means they outnumber us by ten, ten to one in terms of the sheer count of cells. From these numbers, we’re only about 10% human. But wait, isn't it our genes that make us human?

Each of us has around 20,000 to 25,000 human genes, but our microbes also have them, in serious abundance. When it comes to microbial genes, we have between 2 and 20 million!

By these numbers, we are only around 1% human. And back to the original question, how human are we and who is really in control? This information within a relatively new field of study is so incredible and highly connected to the food we eat, because what we eat determines what species of bugs have the potential to grow inside of us. This field of research is rapidly evolving, and up to 70% of the species common in the gut are yet to be examined. This gives us insight into how much is still unknown. I have always found these high numbers of microbes fascinating, and every time we poop, those numbers can change dramatically. Our stool is made up of all sorts of things: bacteria, viruses, fungi, colon cells, indigestible foods, fats and metabolites. But when it comes to the abundance of these different cells, bacteria takes the gold. They make up nearly 1/3rd of your poop.

That's right, every time you take a number two, you are saying goodbye to trillions of bacterial buddies. Human colonies of microbes range from bacteria, fungi, viruses and other microscopic organisms. They live on and in every part of us, and have so forever!

We have different microbe colonies depending on where in or on the body we are talking about. Under your armpit, for example, would have a unique group of organisms, but a centimetre away down your body you have a completely different set of bugs.

Different microbes like different environments, no different to how some people like living somewhere hot, like Hawaii, or somewhere colder, like Iceland. When it comes to two different people, areas like the mouth, nose, armpit or belly button are actually similar in their microbial population. Where we observe significant differences between people is inside our gut. You and I are 99.99% genetically similar, but when it comes to the bugs in our gut, we are 90% different!! This makes what we decide to eat important and unique to us as individuals! The majority of the microbes we have are in the gut, primarily in the large intestine. Approximately 1000 species of bacteria live there, and they weigh around 3-4 pounds, the same as your brain! You may have heard the term “2nd brain,” well that's where it comes from.

This community of microbes in our gut depends on the resources available to them. Animals of different species share similar microbial community clusters depending on their diets, and it's the same for us. A herbivore or carnivore would have similar bug species sitting in their guts to people who share similar diets. The undigested fibre and food particles that make it to the large intestine significantly affect our bacterial populations. When we eat, our many digestive organs attempt to break down food small enough to be absorbed. What doesn’t get absorbed continues the journey to the exit! This is where those bugs lick their lips. When that undigested food comes on, this is their source of nourishment. A simple diet change can significantly change the dominant species within your gut, and different bugs do eat different things. So we want to eat foods that will help the beneficial bugs grow in number and become the dominant health force. There really isn’t ‘bad’ or ‘good’ bugs, it has more to do with the balance of these microbes that is most important.

We know that obese individuals carry certain species in similar quantities to other obese people, making us aware that there is such a thing as an obese set of gut bugs and a lean set. Experiments with mice show that if you put the bugs of a lean mouse into an obese one, larger mice given the right food will begin to become leaner pretty quickly. Healthy gut microbes help us survive, they are far from stagnant, and certainly not pathogenic. A beautiful term to describe this human and gut bacterial relationship is symbiotic. Symbiosis involves the interaction between two different organisms living in close physical association that mutually benefit from the relationship. Humans provide space to live and feed for these microbes.

What do they do for us?

Well, they protect us from disease, help digest our food, and help heal wounds. They also help feed our brains, and have incredible powers that can affect our personality and mood. An unbalanced gut microbiome can cause anxiety and depression. The bugs that we choose to feed and help colonize can affect how we think and feel! These organisms also regulate the way calories are extracted from our food. They produce vital nutrients and help regulate immunity. They have huge influences over hormones, appetite, cravings, genes and brain chemicals. It is clear with all this influence that the microbes are part of our bodies and act like an organ. Just like any other organ in the body, things can go wrong; microbes can cause dis-ease. Not simply gut related symptoms like stomach pain, but mental illness, obesity and heart disease! We have significant power over the potential bugs that we allow to colonize our guts, and many factors can come into play. When we consume or apply an antibiotic substance, we are pretty much wiping out all our bacterial species. Some antibiotics are necessary and life saving, but they are way over prescribed and are actually most abundant in the food industry. Giving animals antibiotics boosts their growth incredibly! Then we eat the animals, and boom, there’s an extra dose of antibiotics for us. Antibiotic soaps and lotions also radically affect vital colonies on our skin.

Many people around the world suffer from a condition known as “leaky gut,” where our gut lining basically opens up, allowing all kinds of large molecules and organisms into the blood where they shouldn’t be. This is a highly inflammatory place to be in, and this type of inflammation negatively affects our microbial colonies.

Most tap water contains chlorine, which acts as an antibiotic, killing off our much needed bacteria. Even having low stomach acid, which is common, will also have a considerable say in whether we have positive bacterial numbers living harmoniously where they should be. Tap water also includes many pharmaceutical chemicals, including antibiotics and birth control hormones. These also affect the microbiome. I wanted this article to be an introduction into the wondrous world of microbes and their symbiotic significance with us lovely humans. Keep an eye out for a follow up article -

Your Bugs & Your Immunity.

Simon Brazier. Dip HN, NNCP


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