Image from Division of Cancer Epidemiology and Genetics
You have a living ecosystem inside of you. Trillions of different bacteria and microbiota are currently alive in your body, in fact according Nature Journal, the ratio of microorganisms that reside in us to human cells is likely to be one-to-one. This makes humans ~holobionts~, pretty neat. Through millions of years of evolution animals have developed a unique relationship with these bacteria and microorganisms in order to survive and thrive. In this post we are going to take a deeper look inside this relationship specifically through the lens of human evolution.
The Microbiome
The microbiome is a name given to the community of microbes that reside in a specific area of our body (i.e. gut microbiome and skin microbiome). We are currently in the midsts of a revolution in terms of our understanding of the human gut and microbiome. Previously there was little known about the different microbes that live within various parts of our bodies, but with the advent of techonological advancements it has allowed for us to get a clearer picture as to what role the microbiome may play in our health physically and psychologically.
How It Developed
When compared with our closests living ancestors, non-human primates and more specifically African Apes, humans have a lower microbiome diversity. Certain species of microbes that we have in relative abundances suggest that this shift occurred when humans began to eat more meat. It has since undergone rapid development and evolution when compared to that of Aftrican Apes (1). We are first exposed to the microbes as we pass through our mothers' birthing canal and begin to grow this living ecosystem through the various exposures and experiences we encounter: environmental, physical, and even psychological.
What Does It Do and Why is It Important?
The microbiome plays very important roles in the regulation, maintenance and development of the human body.
Immune System Regulation
These microorganisms are responsible for controlling most of your immune system. Interestingly, these bacteria, fungi, and microbes communicate with immune cells and help the bodies response to infection and foreign invaders.
Weight Maintence
It also impacts your weight. In one study the researchers looked at the microbiomes from two identical twins. One twin was obese and the other was not they then transferred the two microbiomes into mice using a fecal transplant. They found that the mouse that recieved the microbiome from the twin who was obese gained more weight than the mouse who recieved the microbiome from the non-obese twin. This study suggests that the biosis of the microbiome plays a role in weight maintence.
Brain Health & Mood
Certain species of bacteria produce chemicals in the brain called neurotransmitters. These are the chemical messangers for your brain some examples of neurotransmitters are: serotonin, dopamine, norepinephrine, and acetylcholine. Many of these messangers and their precursors are synthesized in the gut. In fact, it has been shown that up to 90% of serotonin (an antidepression neurotransmitter) is made in your gut. The gut is also physically connected to the brain through millions of different nerves including the vagus nerve. This is called the gut-brain axis, and it communicates mainly from the gut to the brain using these neurotransmitters and gut hormones. This plays vital roles in modulating sleep, energy levels, stress, and mood. Maybe there is some wisdom to the old saying "listen to your gut feeling".
In the next post (Internal natURe: The factors that influence your internal ecosystem) we will discuss what sorts of things impact and influence these trillions of microorganisms inside you and perhaps how you can nurture them to turn on and harness your inner vitality.
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