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The Microscopic Bond: How Microbes Make Us Healthier

How Humans & Microbes Have Co-Evolved

Friends enjoying a meal together

Our microbiomes are extensive, intricately intertwined ecosystems that deserve our daily attention. In this article, we explain the importance of the microbes living in and on our bodies and their impact on our overall health.

For a more practical approach, check out our article about 5 tips to maintain a healthy gut microbiome.

Our bodies are home to trillions of microbes that play a huge role in so many aspects of our health. They’re the little organisms that comprise our microbiomes: the diverse, microscopic ecosystems that aid in things like digestion, nutrient absorption, protection from infection, and even mood regulation.

But this mutually beneficial relationship didn’t happen overnight. You and your microscopic partners have actually evolved together to keep that relationship strong.

Microbes are your long-term partners in health

Microbes play a critical role in ecosystems all over the world — including in our bodies. It is estimated that the human body has roughly 3.8 trillion microbial cells — over 480 times the number of people on earth, and more than the estimated 3.0 trillion cells that make up the body itself (Sender, 2016).

This massive population of microscopic organisms resides within us because we’ve adapted together: humans and microbes share an evolutionary history that is as old as humanity itself. In a 2022 study exploring the relationship between humans and their gut microbes, researchers found that many of our gut microbes evolved in parallel with our genomes. In fact, the microbes residing in our gut actually evolved to specifically adapt to the human environment. Over time, some of those microbes even lost key functions needed to survive, becoming dependent on their human hosts to provide them instead (Suzuki, 2020).

Our bodies provide a hospitable environment for these tiny organisms to thrive. In return, we’ve adapted to rely on them for our own well-being in numerous ways.

Nearly every human system is impacted by microbes

We may commonly associate microbes in the body with our gut and our gut health, but they can have a net positive impact on several systems. In fact, our microbes play a fundamental role in the wellness and function many human systems, such as the six below:

Systems of the body that are influenced by microbes

Digestive System (The Gut): A central gut microbiome promoting healthy metabolism

The gut microbiome is a complex ecosystem that resides primarily in the intestines, providing benefits to digestion, nutrient synthesis, and bowel movements.

For example, gut microbes break down indigestible complex carbohydrates and dietary fibers into short-chain fatty acids, beneficial compounds that are a primary source of energy for colon cells and help with healthy cell turnover. In addition, short-chain fatty acids have incredible benefits to our overall health: increased nutrient absorption, anti-inflammation, protection from gastrointestinal pathogens, and more (Xiong, 2022).

Your gut microbiome can also synthesize vitamins such as thiamine, folate, and biotin. In fact, our body actually relies on our gut microbiome to supply certain key vitamins such as B12 and K. Studies suggest that an imbalanced gut microbiome can lead to vitamin B12 deficiency (Guetterman, 2022). And it’s estimated that up to half of our daily requirement of Vitamin K comes from our gut microbes (Hill, 1997).

Finally, a healthy microbiome leads to healthy bowel movements. A microbiome that’s unbalanced can lead to inflammation and an increased risk of disorders such as constipation, diarrhea, and irritable bowel syndrome (IBS) (Vijay, 2022).

Nervous System - The Brain: A gut-brain “superhighway” that impacts mood & cognition

We all have an enormous communication “superhighway” called the gut-brain axis that connects our central nervous system (our brain and spinal cord) with our enteric nervous system (our gut) (Appleton, 2018). This highway passes neural and chemical signals to and from these organs as well as the microbes in our gut.

What this means is that our gut microbiome can significantly affect our mood, memory, and cognitive functions. For example, various microbes residing in the gut can produce serotonin, dopamine, and GABA — neurotransmitters key for regulating stress and anxiety. Recent evidence even suggests that microbial-produced GABA may play a more significant role in modulating mental health than initially thought (Braga, 2024).

In addition, a 2022 study found a correlation between microbial composition and cognitive function in middle-aged adults: those with higher counts of specific types of microbes exhibited higher cognition than those with lower counts (Meyer, 2022). While this may require further research, it’s nonetheless an exciting finding that further supports a link between our microbiomes and our brain health.

The Immune System: A healthy microbiome for a healthy immune response

As many as 80% of your immune cells are in your gut (Wiertsema, 2021). These cells interact directly with your microbiome to strengthen your immune system. Therefore, your immune system relies on a healthy, balanced microbiome to perform at its best.

Notably, the microbiome trains the immune system to distinguish between potentially dangerous pathogens and beneficial microbes. This not only optimizes your immune response, but lowers the number of inappropriate responses to friendly microbes and other non-harmful substances, reducing unnecessary inflammation, allergies, and food sensitivities.

A diverse gut microbiome also can prevent the harboring of pathogens within the gastrointestinal tract. Certain microbes help foster conditions that aren’t conducive to pathogenic growth, reducing the chances of infection and sickness.

Integumentary System - The Skin: An important external microbiome

Our skin is often the first line of defense against infection and sickness, and one of the key factors in its effectiveness is its microbiome.

For example, skin may serve as a physical barrier to prevent the entry of pathogens, but our microbiome adds an extra layer of protection by keeping our skin’s pH at a level that’s undesirable or even harmful to germs (Grice, 2011).

Additionally, the skin’s microbiome serves as a warning flag for the immune system, similar to that of the gut microbiome. It effectively distinguishes between helpful and harmful microbes on your skin, initiating an immediate immune response if it detects any harmful organisms (Byrd, 2018).

Emerging evidence also suggests that the skin microbiome is crucial to the wound healing process. For example, one key microbe in particular, Staphylococcus epidermidis, plays an important role:

  • It effectively shields wounds from being infected by pathogens
  • It protects wounds from other microbes which may slow down healing
  • It helps modulate inflammation and signals immune cells to accelerate wound closure (Leonel, 2019)

Respiratory System - The Lungs: A unique microbiome that supports respiratory health

It was long thought the lung was a sterile organ without a beneficial microbial population: the first evidence of the lung microbiome was only recently reported in 2010 (Chen, 2023). Since then, we’ve learned that the lung microbiome indeed exists, but it’s wholly unique from other microbial populations: it’s more dynamic & fluid rather than robust & self-sustaining due to its high rate of turnover.

As a result, the data connecting a healthy lung microbiome to health is scant — simply because we haven’t really been able to define what a healthy lung microbiome looks like. Interestingly, preliminary data suggests that those with stronger respiratory health have lung microbiomes that are similar to their oral microbiomes (Whiteside, 2021).

We’ve also come to learn that, in addition to the gut-brain axis, there’s also a gut-lung axis: a complex pathway connecting their respective microbiomes. This connection indicates a correlation between gut microbes and lung immunity. For example, an unhealthy, imbalanced gut microbiome may result in chronic inflammatory respiratory disorders such as asthma and chronic obstructive pulmonary disease (COPD) (Frati, 2019).

Oronasal System - Mouth and Nose: Beneficial microbes key to more than oral hygiene

The inner linings of the mouth and nose are abundant with diverse microbial communities that play a critical role in preventing infections. In a healthy mouth, these microbes maintain a balanced ecosystem that effectively suppresses the growth of pathogenic bacteria.

Conversely, an unhealthy mouth experiences a disruption in this microbial balance, which can lead to a significant trickle down effect that impacts not just your oral health.

An overgrowth of harmful bacteria can lead to serious oral diseases — and studies have shown that those with periodontal diseases such as gingivitis have a significantly higher risk of developing heart disease (Leng, 2023). Additionally, because your oral microbiome is connected to your gut microbiome, the overgrowth can travel to your gut and cause additional imbalances there, resulting in further gastrointestinal health issues (Park, 2021).

In other words, keeping your oral microbiome balanced isn’t just important for your oral health; it’s important for your overall health.

Small but mighty microbes are essential to our overall health

The microbial populations that call our bodies home are more important than we know. As new studies come out, it’s clear that our microbiomes are absolutely essential to our overall health and optimal function — perhaps in ways that we haven’t even discovered yet.

Let’s take this as a phenomenal opportunity to give some attention and care to our microbiomes. It’ll most likely pay dividends for our continued well-being.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice.