What Are Gut Bacteria And Why Are They Important?

Gut bacteria are those bacteria that live inside the digestive system of all animals, including humans. We’ve found that these bacteria are crucial to our health, both physical and mental. They help us digest food, provide us with nutrients and help us fend of pathogenic bacteria.

Simply put – gut bacteria, also known as the gut microbiota, are the bacteria present in our bodies lined across the inner walls of our gastrointestinal tract. There are about 300-500 bacterial species in the human gut with their average population being 100 trillion. That’s enough to fill twelve thousand, six hundred and fifty-eight Earths at our current population. Initially, that was thought to be ten times the number of human cells in our body but new research suggests the ratio of bacterial cells to human cells could be 1.3:1.

You may be learning a lot about gut bacteria in the news, social media, and many science channels. We’ve only recently started to understand their role in our bodies and they are more important than we could imagine.

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Where does it all begin?

When babies are still in the fetus stage inside the mother’s uterus, bacteria start to colonize and form settlements in their guts. These bacteria are similar to the mother’s and they enter the body when the baby swallows amniotic fluid. Once settled inside, the gut bacteria start planning their settlements but only start to build them after the baby is born.

After the baby’s born, more bacteria enter the gut, especially at birth. During the delivery, the bacteria present in the mother’s vagina make their way inside the babies mouth and try to colonize themselves inside. In fact, C-section babies have a different gut microbiota compared to their naturally born counterparts.

Unfortunately, all the bacteria that enters the baby’s gut isn’t good. Sometimes even bad disease-causing bacteria can enter. However, there is a simple solution – breastmilk. The mother’s breastmilk contains everything a baby needs to grow big and strong.

One breastmilk component is antibodies. When babies are born, their immune system isn’t well developed. These antibodies protect the newly born babies till their immune systems learn to fight for themselves. One of the ways they do that is by teaming up with the good bacteria to fight the bad bacteria and prevent them from lining inside the baby’s gut.

Additionally, breastmilk has human milk oligosaccharides which are sugary molecules meant to boost good gut bacteria growth. It’s a natural prebiotic that helps increase the population of Bifidobacterium – the bacteria largely present in a baby’s gut.

As the baby grows older and starts eating solid foods, the gut bacteria start to party. All these new foods bring newer and newer gut bacteria inside the baby’s system where they can mingle with each other. The new foods also bring new nutrients that support the growth of such different gut bacteria. This is why eating a healthy diet is so important. Even research shows that eating too much non-nutritious junk food causes imbalances in our gut bacteria.

The new bacteria species that start to make themselves at home are Bacteroides, Ruminococcus and Clostridium. Then as babies turn three, their guts settle down and becom5e adult-like.

Why is this procedure so delicate and important? It’s because gut bacteria have enzymes that help break down difficult to digest food and help make vitamins our bodies are incapable of doing! Without gut bacteria, our body would face vitamin deficiencies and suffer from indigestion and growth defects.

The gut bacteria colonization process in growing babies

The gut bacteria colonization process in growing babies. (Photo Credit : ScienceDirect)

What other processes do gut bacteria participate in?

We just talked about how gut bacteria help in digestion but they don’t only do it in the infancy stage. Throughout our entire lives, gut bacteria help digest food.

On average, each person passes 60 tonnes of food through their GI tract in their lifetime! That’s as heavy as ten elephants or a fully fuelled aeroplane. Our gut bacteria grind non-stop by helping us break down complex sugars like starch and other polysaccharides. In doing so they make the B group vitamins and vitamin K which they release into our intestinal environment, where it is absorbed by our own cells. We should thank our gut bacteria as we need these vitamins for our body to stay healthy.


Our twelve essential vitamins. (Photo Credit : OlgaChernyak/Shutterstock)

But how do gut bacteria perform such helpful tasks? They have the genes for it and all these genes make up what we know as the gut microbiome. Interestingly more than 99% of the genes in our body are microbial.


Apart from digestion, gut bacteria also play a role in our sleep cycle. Studies found that gut bacteria would release sleep-inducing compounds called muramyl peptides.

Other studies found that sleep-deprived people showed changes in their gut bacteria.

Some gut bacteria like Corynebacterium after feeding on the food we eat produce metabolites like serotonin. This produced serotonin is released into the blood and interacts with the nervous system which signals the brain to control the sleep/wake cycle.

If you find yourself suffering from poor sleep quality for an unknown reason, it could be because your gut bacteria are disturbed.

If your gut bacteria can’t sleep well, neither can you.

Gut-brain axis

Apart from helping us digest and sleep well, the gut microbiota also communicates with the brain. That’s right, all the gut microbes have our brain on speed dial and they help coordinate our body’s functions. This is known as the gut-brain axis. It’s the two-way communication between the central and enteric nervous systems allowing the gastrointestinal tract and brain to talk to each other to regulate homeostasis.

Neurons in the GI tract, send signals to the brain coordinating physiological functions and even immune responses to germs. That’s how gut bacteria are able to affect the way we behave, think and interact.

One study that worked on special female mice that were without gut bacteria found that they had lower anxiety levels when they were inside mazes. In males, however, there was a stronger stress response. This led scientists to believe that the gut-brain axis differs amongst gender.

So, depending on how healthy our gut bacteria are, it can affect our brain signalling, affecting our hormonal responses. This is why sometimes when you have indigestion or stomach problems, you could be feeling a lot of anxiety or irritability.

How can we increase our good gut bacteria’s strength?

Apart from maintaining a good healthy diet, we can help strengthen the good gut bacteria using two tools; probiotics and prebiotics.

Probiotics are essentially good bacteria that we put in our bodies, in numbers high enough actually to have a beneficial effect. These include Bifidobacterium species and other Lactic Acid Bacteria species. These bacteria can be consumed by taking capsules or eating probiotic foods like cheese, yoghurt and other bacteria rich foods.

Prebiotics are slightly different. These are foods used by good gut bacteria to help boost their growth and strength. Like any other living organism, Gut bacteria like their fair share of treats. Giving them prebiotics like inulin, fructooligosaccharides or galactooligosaccharides allows the good gut bacteria to grow better.

However, before trying any of the two, it is important to consult your doctor to find out which probiotics or prebiotics are suitable for you.


Sources of probiotics and prebiotics. (Photo Credit : Natasha Markina/Shutterstock)

A final word

I hope you’re beginning to understand now just how important gut bacteria are to us. They are more than just germs that help us digest food. They help control our body’s functions in unimaginable ways. Studies are finding connections between disturbed gut bacteria and neurological conditions such as Alzheimer’s and autism.

That’s why so much research focuses on better understanding the gut-brain connections. Previously, brain disorders were considered incurable, but now there is hope that we can treat these conditions better by modifying gut bacteria.

Many companies are out there that can give you details about your gut bacteria based on your stool samples. All you have to do is send them a bag of poop and they will isolate all the bacterial strains from it and sequence them to let you know how healthy your gut is and what kind of bacteria you have inside.

Our gut bacteria do so much for our body that we don’t understand yet. But what is clear is that by optimising the relationship between our body and our gut bacteria, we can become mentally and physically stronger.

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About the Author

Armaan Gvalani holds a Masters in Biotechnology from Symbiosis International University (India). He finds the microscopic world as fascinating as the business of biology. He loves to find practical applications from scientific research. When not peering into his microscope or nurturing his cultures, he can be found smashing a ball around the squash court or doing laps in a pool.


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