Thousands of microscopic organisms live in our bodies, impacting our behavior in ways you’d never expect. Bacteria and fungi are present all over your body. But don’t worry: most of them are there to keep you alive—welcome to the world of the human microbiome.
What is the microbiome?
The human body is formed of around 30 trillion human cells, but our microbiome is an estimated 39 trillion microbial cells that live on and inside our body. Because of their small size, these organisms account for only about 1–3 percent of our total body mass.
Where is the microbiome?
The human body has many diverse environments, and microbes are capable of living in all of them. Each part of the body has a different environment and forms a different type of ecosystem, like a continent with different countries and climates, and whose inhabitants have adapted to the characteristics of each location.
Our faces and hands are dry and cool. They’re exposed to a constant stream of microbes every time we touch anything.
Nooks and crannies like the armpits are moist, warm, and dark therefore constituting a good place for bacteria to live.
The average human foot is even better, with 600 sweat glands per square centimeter – hundreds more than the armpits – it constitutes a perfect environment for a colony of bacteria.
And finally, the gut microbiome where thousands of bacteria live in symbiosis with us and are known as the gut microbiome.
Where do these microbes come from?
Your mother is responsible for three-quarters of your microbiome. The womb is a sterilized place, free of microbes (at least we think so at the moment). But during birth, when we cross via the birth canal, we are exposed to all kinds of vaginal microbes. Babies born through cesarean section are more prone to having allergies, asthma, celiac disease, and obesity later in life.
When we grow up, we start ingesting around a million microbes in every gram of food, and our diet has a direct impact on which species thrive in our gut microbiome; when we switch from a meat-eating to a vegetarian diet, our gut bacteria changes.
Similarly, as we go through life, moving from one environment to another, we get exposed to microbes from different people and places. Every home has its microbiome, which is shaped by the inhabitants. After moving into a new home, just after 24 hours, we colonize it with our microbes. Those who grow up in a home with pets are also exposed to a large variety of germs, which isn’t necessarily a bad thing.
Lack of exposure to such microorganisms is thought to be the cause behind many common allergies.
What does our microbiome do?
The microbiome has a lot of roles. The gut microbiome plays a role in fat storage and nutrient absorption. These helpful microorganisms help also protect the gut and skin barrier and assist in replacing damaged and dying cells with new ones. Hence, their vital is their role in preventing illness. Our good microbes protect us against hostile microbe invaders, helping us to prevent many diseases and inflammatory conditions.
The human microbiome even affects how we smell. Different microbe species might convert sweat into the smell of onions or testosterone into the stink of urine, which act as powerful signals for our friends and foes. These smells are highly personal; studies have found people can be identified just by their sweaty T-shirts.
Does the microbiome affect behavior?
It’s hard to tell if the microbiome causes changes in diseases and behavior or if diseases and behavior cause changes in the microbiome and maybe both.
It’s hard to tell if the microbiome causes changes in diseases and behavior or if diseases and behavior cause changes in the microbiome and maybe both.
Experts are piecing together how gut microbes influence the brain through the hormones and molecules they produce and more evidence is growing on the gut-brain relationship.
So, if you haven’t been paying attention to the health of the good microbes that live on your skin and inside your digestive tract, now is a great time to start!
