From the moment we are born, our bodies become a prime destination for an incredible variety of microbes. These tiny life forms — bacteria, fungi, and viruses — begin colonizing us right away, starting with the process of us being born, followed by skin contact through our mother’s touch, just as mother’s milk is introduced into our system.
Trust your gut, your health depends on it

This early microbial exposure plays a crucial role in shaping our immune system, influencing our health and development throughout our lives. As we grow, we encounter more microbes from everything around us — people, food, and even the surfaces we touch. Some of these microbes stick around for good, establishing permanent homes in various areas of our body, such as our nose, mouth, gut, skin, and genitals. Collectively, these microbial communities are known as microbiomes. And among all these microbiomes, the gut microbiome is the most populated3.
This is where our story begins — inside the gut, home to billions of microbes that shape not only digestion but also immunity, metabolism, and overall health. By the time you finish reading this, you may find yourself rethinking what it means to have a “gut feeling.”
The Gut, A Prime Real Estate for Microbes
The ‘gut microbiome’ typically refers to the community of microbes in organs like the esophagus, stomach, small intestine, and large intestine. However, the large intestine, or colon, is where most of the action happens. This area is the most densely populated microbial habitat in the body. For example, while each milliliter of fluid in the large intestine can contain anywhere between 10 billion - 100 billion bacteria4, the numbers drop dramatically in the small intestine to around 10,000 - 100 million bacteria per milliliter, and less than 1,000 bacteria per milliliter in the stomach.
This significant concentration in the large intestine is why so much of the research on gut health focuses on this part of the body, which is not only the most densely packed with microbes but also plays a central role in maintaining our overall health.
So, what does all this mean for you and your health? Let’s explore the importance of these microbes and their roles in our well-being.
Why Does the Gut Microbiome Matter?
If you gathered all the bacteria from your gut microbiome and weighed them, you’d find they add up to around 1-2 kilograms⁵ — roughly the weight of your liver. That’s a lot of microscopic beings! But it’s not just about the sheer number of microbes in the gut; it’s about the vital roles they play.
But that’s not all. The gut microbiome also plays a starring role in immune health. Around 70-80 percent⁶ of the body’s immune cells reside in the gut. This makes a thriving microbiome essential for defending against infections and maintaining overall immunity. And it doesn’t stop there. As we learn more about the science of the microbiome, we realize how many diseases are linked to microbiome: lifestyle diseases, including diabetes, obesity, and cardiovascular disease.
Indeed, as researchers continue to unravel the complexities of the gut microbiome, we’re discovering more about how these microbes influence nearly every aspect of our health. While the science is still evolving, one thing is clear: a healthy gut microbiome is crucial for our well-being.
Let’s now dive into one of the most fascinating aspects of gut health: the Gut-Brain Axis.
The Gut-Brain Axis
One of the most fascinating revelations about the gut microbiome is its role in the "Gut-Brain Axis" — a constant communication channel between your gut and brain that they use to regulate each other. When your gut is happy, it can positively affect your mood and mental state; conversely, an unhappy brain can lead to issues like constipation.
You may be wondering how your gut, which you’ve always thought of as the place for digestion and waste elimination, can possibly communicate with the brain.
The gut contains a vast network of neurons—tiny cells that, when connected, form nerves and help transmit signals throughout the body. In fact, there are about 600 million neurons⁷ in the gut, and this complex network is called the Enteric Nervous System (ENS). So independent and sophisticated, the ENS is often referred to as the "second brain"⁸. It’s the only part of the body, outside the brain, with such a highly developed network of neurons. The ENS manages everything from moving food through the digestive tract to monitoring gut health in real-time—without needing direct input from the brain.
But this doesn't mean the ENS works in isolation. It communicates with the brain every second through the Vagus nerve — a kind of superhighway for signals traveling between the gut and the brain. This two-way communication explains sensations like "butterflies in your stomach" when you’re nervous, or the gut discomfort you may feel during stressful times.

Research into the gut-brain axis has made one thing clear: microbes don't just live quietly in your gut; they are active, vocal contributors to your brain's health and emotional well-being.
Now, given this constant chatter between the gut and brain, do you think the trillions of microbes in your gut will remain passive? Absolutely not! These gut microbes are active participants in this ongoing dialogue. They produce chemicals that influence brain function, affecting mood, mental health, and stress levels. Conversely, a stressed brain will send signals that affect your gut, potentially causing problems like constipation or bloating. It’s a dynamic, bidirectional system where the state of your gut microbiome directly impacts how you feel — and vice versa.
Research into the gut-brain axis has made one thing clear: microbes don't just live quietly in your gut; they are active, vocal contributors to your brain's health and emotional well-being. This connection is facilitated by a variety of direct and indirect pathways, and the effects are more profound than we ever imagined.
Let’s explore a few examples of how microbes in your gut influence your health through the Gut-Brain Axis.

Mood Influencers and Mental Health Champions
Ever felt a sudden burst of calm after a deep breath, or that rewarding thrill when you hit a personal goal? Those feelings — whether it’s relaxation before tackling a challenge or the sense of achievement afterward — are fueled by chemicals in your body called serotonin and dopamine. Often referred to as the "feel-good" chemicals, they are crucial for maintaining mood, motivation, and emotional balance.
But here’s something surprising: your gut has a significant role in the production of these mood-regulating chemicals. It’s not just a silent bystander digesting food and processing waste — it’s a bustling hub of activity that teams up with the microbes living inside it to influence your mental well-being.
At any given time, your gut hosts around 500–1,000 species9 of bacteria, and among these, some like Lactobacillus, Bifidobacterium, and Staphylococcus play key roles in influencing serotonin and dopamine levels in your body. But how do these tiny microbes, living so far from the brain, manage to influence your mood? Let’s break it down.
Direct Impact: The Gut as a Serotonin Factory
The gut is home to special cells called enterochromaffin (EC) cells. Think of these as tiny factories that produce serotonin with some help from the bacteria in your intestines. While this serotonin doesn’t directly enter your brain — it’s mostly used to regulate gut functions — it still plays a vital role in gut-brain communication.
How does it work? Through the gut-brain axis, a two-way communication system that constantly shares information between your gut and your brain. Serotonin from the gut can signal the brain to stay calm or sound the alarm if something is off, like low levels of serotonin in the body. When your gut microbes are thriving, these signals work like a charm, keeping stress in check and emotions balanced.
But if your gut’s microbial ecosystem becomes unbalanced — a condition known as dysbiosis — serotonin production can falter. This imbalance doesn’t just affect your mood; it can also lead to physical symptoms like constipation or Irritable Bowel Syndrome (IBS), a condition that affects about 1 in 10 people worldwide10.
Indirect Impact: Microbial Support for Mood Molecules
Your gut microbiome is an active participant in keeping your mental health balanced. One way it does this is by producing critical chemicals such as Tryptophan and Tyrosine — known as ‘precursors’ because they are the raw materials your brain uses to create serotonin and dopamine, as it cannot use the serotonin and dopamine produced inside the gut. Bacteria like Lactobacillus and Bifidobacterium produce precursors by breaking down proteins in the food we eat.
If the gut microbiome gets disrupted, the production of these critical precursors can plummet, leading to reduced serotonin and dopamine levels. This imbalance might manifest as mood swings, anxiety, or even depression. On the flip side, a healthy, diverse gut microbiome ensures a steady supply of these building blocks, keeping mental health in check.
Beyond the Gut-Brain Axis
The influence of your gut microbiome goes far beyond just connecting to the brain—it plays a key role in several critical functions, including immunity, cancer risk, and metabolism.
Your immune system acts like a defense army, always on the lookout for invaders. The bacteria in your gut help train immune cells to differentiate between harmful pathogens and harmless substances, ensuring the immune system doesn’t attack the body itself. However, when the balance of gut microbes is disrupted, it can lead to chronic inflammation.
What is chronic inflammation? It is like an alarm that keeps ringing even after the threat is long gone, signaling an ongoing issue that the body hasn't resolved. This can cause the immune system to mistakenly attack the gut, leading to conditions like Crohn’s disease, Ulcerative colitis, rheumatoid arthritis, and neurological disorders.
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Maintaining a healthy balance of gut microbes is crucial for overall well-being.
Various laboratory and animal studies have linked the gut microbiome to cardiovascular diseases and Type 2 diabetes, and now research is focused on uncovering any direct causal links to develop targeted therapies12.
Emerging research is also revealing how our gut microbiome might influence cancer development and its role in anticancer therapies. For instance, bacteria like Fusobacterium nucleatum and Helicobacter pylori have been linked to an increased risk of stomach cancer13.
Maintaining a healthy balance of gut microbes is crucial for overall well-being. But did you know that the food you eat plays a direct role in shaping that balance?
You Are What Your Microbes Eat
Your gut is home to trillions of microbes, and they are dependent on the food you consume. However, they are not just there living off the food we consume – in return they give us something that makes us healthy; it's a mutually beneficial relationship, known as symbiosis. When you eat, your gut microbes feast on the food you consume, and to return the favor, they produce essential chemicals like neurotransmitters that help regulate various functions in your body. But here’s the catch: if your diet doesn’t provide the right nutrients for these microbes, their ability to support your health can diminish, and the consequences can be significant.
Consider the example of one of the most important bacteria of the gut microbiome, the Bifidobacterium, which begins to populate the gut shortly after birth14, entering via the vaginal canal during a natural delivery or through breast milk.

Numerous benefits to the baby in Bifidobacterium that thrive on special compounds, including obtaining energy from the breastmilk.
There are Bifidobacterium that thrive on special compounds found in breast milk called human milk oligosaccharides, and in return, they provide numerous benefits to the baby, including obtaining energy from the breastmilk, training and helping our immune system develop, and encouraging the growth of other beneficial gut microbes. This mutual relationship underscores how food directly impacts gut microbes and overall health.
However, studies have found that the population of Bifidobacterium and other good bacteria in our gut tends to reduce as we get older – particularly in combination with poor dietary choices, not least those rich in processed foods, high in sugar, and low in fiber, which accelerates this decline. Antibiotics can also disrupt the gut microbiome by wiping out both harmful and beneficial bacteria like Bifidobacterium.
This decline in Bifidobacterium highlights a broader issue: poor dietary habits and overuse of antibiotics can weaken the gut microbiome as a whole, reducing its ability to support not only physical health but mental well-being as well.
But it’s not only Bifidobacterium that suffers. Other essential microbes can also decline due to similar dietary and lifestyle factors. When the diversity of microbes in the gut decreases, the microbiome loses its ability to maintain balance and perform essential functions, affecting everything from digestion to immune function.
With the understanding that the health of our gut microbiome hinges on the foods we consume, it's clear that the future of gut health is not just in what we eat, but also in the innovative solutions we can incorporate to nurture it — enter biosolutions.
Biosolutions for Your Gut Health
The intricate partnership between humans and their gut microbes is a cornerstone of health, and science is uncovering natural ways to support this balance through biosolutions – innovative methods that work with your body instead of against it. Unlike treatments that may disrupt the natural systems in your gut, biosolutions aim to enhance and restore harmony within your microbiome.

One of the most widely recognized biosolutions is probiotics, found naturally in e.g. yogurt.
One of the most widely recognized biosolutions is probiotics, which are live beneficial bacteria introduced into the gut through food or supplements. You’ve likely heard about probiotics in foods like yogurt, kimchi, or kefir, which naturally contain these helpful microbes. Probiotics are also available as specialized products, often in capsules or powders, designed to deliver targeted health benefits.
For instance, supplements containing Bifidobacterium longum 35624™ have shown significant success in alleviating common digestive discomforts like bloating, abdominal pain, and irregular bowel movements16. Similarly, Limosilactobacillus reuteri has demonstrated remarkable benefits for people dealing with stomach discomfort caused by Helicobacter pylori, helping to create a healthier gut environment by reducing the population of harmful bacteria17.
Probiotics do more than address digestive issues. Emerging research has identified a fascinating class of probiotics called psychobiotics, which specifically influence the Gut-Brain Axis – the communication link between your gut and brain. For example, Bifidobacterium longum 1714™ has shown potential in helping people manage stress, improve sleep quality, and even enhance mood, offering a new dimension to how we think about mental and physical health18.
But probiotics are only the beginning. Scientists are identifying an ever-growing list of beneficial microbes within the gut microbiome, each playing a unique role in maintaining health. Many of these microbes are now isolated, studied, and developed into safe and effective biosolutions that can be tailored to individual needs.

The future holds the promise of treatments customized to each individual’s microbial ecosystem.
What makes these advancements even more exciting is the prospect of personalized medicine. Every person’s microbiome is as unique as a fingerprint, and the future holds the promise of treatments customized to each individual’s microbial ecosystem. Such precision healthcare could revolutionize not just how we treat disease but how we maintain health, moving from symptom management to prevention and optimization.
As we delve deeper into the secrets of the gut microbiome, it becomes clear that a healthy life begins with a healthy gut. By supporting the trillions of microbes working tirelessly on our behalf, we’re unlocking a new era in medicine—one that honors the delicate yet powerful partnership within us.
Food cravings? You can blame it on the gut microbes
Ever feel like your cravings are totally out of your control? Your gut microbiome, those trillions of tiny bacteria living inside you, could be pulling the strings. 1. For example, if you're constantly craving chocolate, it might be because your gut bacteria are whispering sweet nothings into your brain. Studies have shown that people who crave chocolate have different microbial metabolites in their urine compared to those who don’t crave it—even when they eat the same food2! So next time you’re reaching for that extra piece of chocolate, blame it on your gut microbes!
Couples who stay together, gut together
Ever wondered if your relationship is making you healthier? Turns out, it might be—on a microbial level! A study integrated into the Wisconsin Longitudinal Study4 found that the quality of your social bonds, especially with a spouse, could influence the diversity of your gut microbiome. Researchers analyzed microbiota data from 94 married couples and 83 sibling pairs and found that couples, particularly those with close relationships, shared more similar microbiomes than siblings.
Not only that, married couples reported greater microbial diversity and richness compared to those living alone—especially when they had close relationships. This suggests that your social ties, especially close marital bonds, could be influencing your gut health, possibly contributing to the health benefits long associated with marriage.
Play a Tune, Boost Your Gut!
Your gut might have a hidden love for music! A recent study on mice revealed that playing music during feeding led to significant changes in their gut microbiota. The music increased populations of beneficial bacteria, like Firmicutes, while decreasing harmful or conditionally pathogenic bacteria. Looks like a good playlist could be the key to happier, healthier guts—
Is Your Gut Making You Angry?
Did you know your gut microbes might influence your level of aggression? A recent study6 found that mice with altered gut microbiomes—either from being germ-free or treated with antibiotics—showed increased aggression. Even more fascinating, when researchers transplanted gut bacteria from infants exposed to antibiotics into other mice, those mice became more aggressive too. The study suggests that the gut microbiome plays a key role in regulating aggression, potentially through its impact on serotonin levels and brain function. So, next time you're feeling a bit extra, it could be your gut microbes calling the shots

You’re never alone, there’s a world within you
Would you believe that tiny organisms inside your body influence how well you sleep, the state of your mental health, your immunity, and even your overall physical well-being?
No, we’re not talking about miniature aliens sitting in you and orchestrating your life like a sci-fi thriller — this isn’t Men in Black! Instead, we’re referring to the bacteria, fungi, viruses, and other microbes that call your body home.
What is a biosolution?
Microbes and enzymes are tiny but mighty agents of change. For billions of years, they’ve enabled transformation in all living things through microbiology.

What are biosolutions? Where do they come from?
How do they work? What would the world look like without them?
Get the answers to these questions and more from the monthly biosolutions bulletin. Whether you’re an expert who wants to keep on top of the latest innovations or just starting to learn about biosolutions, we’ve got you covered.
With stories ranging from the role of biosolutions in food security to how they enable NOMA-style dining experiences, there’s something for everyone.
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Sources:
1. Breastfeeding from the first hour of birth: What works and what hurts
3. An expanded reference map of the human gut microbiome reveals hundreds of previously unknown species
5. The critical role of gut microbiota in obesity
7. The Enteric Nervous System and Its Emerging Role as a Therapeutic Target
9. Current understanding of the human microbiome
10. Global burden of irritable bowel syndrome: trends, predictions and risk factors
11. Think Twice: How the Gut's "Second Brain" Influences Mood and Well-Being
12. Bacteria in our gut could play a role in cardiometabolic disease: A new initiative aims to find out
13. Role of the gut microbiota in anticancer therapy: from molecular mechanisms to clinical applications
14. Gut microbiome: meet Bifidobacterium breve, keeping babies healthy
15. The role of Bifidobacterium in longevity and the future of probiotics
16. IBme™
17. Pylopass™
18. ProbioBrain™
Trivia:
How Gut Bacteria Tell Their Hosts What to Eat
Got food cravings? What's living in your gut may be responsible
The composition of the gut microbiota could influence decision-making
Close social relationships correlate with human gut microbiota composition
Music-based interventions in the feeding environment on the gut microbiota of mice