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How 100 Trillion Bacteria in Your Gut Keep You Healthy

Let’s hear it for the microbiome!

We spoke to Annick Mercenier, a scientist at the Nestlé Research Center in Lausanne, Switzerland about the microbiome, or gut bacteria, that keeps our body healthy. Here’s what she had to tell us about friendly bacteria.

I am one of many scientists around the world whose work involves studying an ecosystem of diverse species. Some of these species are already known to us, others have never been cataloged before.

This ecosystem is not deep in a rainforest, or miles under the sea. It’s inside you.

It’s the human gut ‘microbiome,’ the vast colony of microbes that inhabit your gastrointestinal tract.

Mutual benefit

The average healthy adult has up to 4.5lbs of bacteria in their gut, made up of thousands of different species.

With all these different species, it means you and I actually have more bacterial genes than human genes.

However, we’re not simply providing that bacteria with somewhere safe to live. They also help us by playing an important role in keeping us healthy.


We know there is a two-way communication between our gut and our brain.

The gastrointestinal tract is sometimes referred to as the human body’s largest immune organ or the ‘little brain’ within us. It has up to 80% of our antibody-producing cells and is a vital part of our defense system. It also happens to be a ‘high-traffic’ channel.

Throughout our lives we consume things, inhale things, and swallow things, sometimes by accident.

Some of the microbes living in our gut may be native to us. Others might just be passing through. They may be helpful, or harmful.

Immune response

When we’re born, our gastrointestinal tract is sterile, or almost sterile. In the first few minutes after birth, microbes begin to occupy it. Recent studies suggest this might even start in the womb.

Evidence points to the fact that this early microbial colonization helps our body to defend itself against disease.

Very early on, our immune system must learn not only to recognize when a pathogen has entered the gut, but also to provide a quick and effective response.

The gut’s ability to function properly depends on the interactions between its three main components: the microbes, the intestinal barrier, and the immune system.

By studying this ‘cross talk’ we can better understand how certain microbes in our gut can help to maintain our health and why interfering with them may lead to problems.

Hygiene hypothesis

We’re much more hygienic than in previous decades. Although this has brought many public health benefits, it is not necessarily always a good thing.

Many scientists believe some aspects of modern life designed to make us cleaner and healthier may in fact be interfering with the microbes in our gut.

Antibiotics, for example, have been essential to society’s ability to fight infections, but we now know that repeated courses can upset the gut microbial balance. And it’s not just medicines. What we eat and all the substances around us can have an impact.

Technological breakthrough

Although each of us has a unique composition of microbes in our gut, we share a ‘core’ microbiome as human beings.

It’s thanks to high speed DNA sequencing that we now have such a huge amount of information at the molecular level about what types of bacteria make up our core gut microbiome.

Today, the challenge for scientists is to integrate this mass of data that has been generated worldwide to fully understand what constitutes a healthy gut microbial balance.

Research has taken us to the point where we can say that we know which microbes are in there and, to some extent, what they are doing.

What we don’t yet have is a complete picture, especially as the gut contains a number of bacteria we have yet to identify. The Nestlé Research Center, where I work, and the Nestlé Institute of Health Sciences are involved in a number of scientific collaborations that are that are trying to fill in the gaps and unlock information that can help with effective personalized nutrition and addressing health conditions.

It’s an exploration that’s only just beginning.

This article was originally published on




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