There Are More Bacteria Living Inside of Us Than Our Human Cells

Here’s how to make them thrive.

Photo by CDC on Unsplash

It’s a hobby many of us like to have. We can grow and cultivate our environment, it’s always more enjoyable when the weather is nice, and we can reap the ‘fruits’ of our labor. Of course, I’m referring to our gut microbial ecosystem. The folks outnumber our genome by a factor of 10–100 to 1. For those to who this is breaking news, do not worry. For it seems like every day, new data is coming out on how our gut bugs can make us healthy, unhealthy, and even some species that can be either healthy or unhealthy depending on how many there are. But how does this happen? How can some bugs make us healthy? Can certain species contribute to diseases such as autoimmunity and diabetes? How did they get there? What can we do to cultivate our ‘garden within’?

Learning the players.

The gut ecosystem is a crowded and highly coveted ground where bacteria, viruses, protozoa, fungi, and helminths (worms) compete for residence. Many of those things may sound scary, but know that humans have been co-evolving with these creatures since the beginning of time. If they weren’t supposed to be there, evolution would have made it so. For this article, we’re only going to be talking about bacteria.

Most of our gut bacteria live within our colon (Large Intestine). The colon is one of the most densely populated areas in terms of bacterial cells on Earth, with concentrations of 10^12 (that’s a lot of zeros) (1). Our small intestine does house some bacteria, but nowhere near the degree of the large intestine. People with bacterial concentrations greater than 10^3 (not quite as many zeros) in the small intestine may be diagnosed with SIBO (Small Intestinal Bacterial Overgrowth).

These bacteria encode more than 3 million genes compared to only 23,000 in the human genome.

Their functions include, but are not limited to, absorption and creation of vitamins, keeping our immune system intact, and fighting off harmful bacteria that try to colonize us. Those who have taken biology or a microbiology class may be familiar with the naming system for bacteria. Great news for all involved; we’re not going to touch on that. Our gut bacteria are classified based on several subgroups with similar genetic makeup.

Everyone’s microbiome is unique to that individual.

Let me say that, again, everyone’s microbiome is unique to that individual. Even biological twins will have differences in their gut bacteria. Logical next question, what determines what type of bacteria we have? Answer. What doesn’t?

Microbial Influences

It all starts on your birthday, while you’re in the mom’s belly, or it all begins with the health of your mom’s microbiome. Not much you can do to affect your mom’s health before you were even a thought (maybe if Elon Musk invents this time machine he always talks about, who knows). Two significant events that happen early in life are vast predictors of your bacterial balance: 1) Whether you were born vaginally (normal birth) or via C-section, and 2) Whether you were breastfed as a child. Babies born vaginally and fed breast milk have greater diversity in their microbiome than those born via c-section or fed artificial formula (1).

When it comes to the gut biome, diversity is a huge factor. Eating a nutrient-dense diet, getting the right amount of exercise, sleeping well, and even having a positive mental state are all ways to alter its diversity. Gee that sounds like all the stereotypical stuff we’re told to make us healthy. You’re right. What’s fit for you (the host) is likely the most beneficial for the microbiome. Vice versa, long-term antibiotic use, not exercising, eating a small diversity of foods, and not being in a good mental state can potentially decrease the diversity of our gut biome. Diversity is reduced in conditions such as Irritable Bowel Syndrome (IBS), obesity, chronic pain, and Alzheimer’s (2). Patients with autoimmune diseases such as Rheumatoid Arthritis, Lupus, and Multiple Sclerosis have a different microbiome than healthy individuals (3).

Okay. Cultivating my gut garden is essential. Now what?

Let me start by saying if you suffer from autoimmune conditions, digestive ailments, chronic pain, or chronic stress, seek a qualified physician trained to look for the root cause of your situation, such as a Functional Medicine Practitioner.

Every time we eat, a change takes place in our microbiome. If we take people eating a standard American diet and switch it to either a plant-based or animal-based diet, markers for gut diversity change within the first day (4). You may think the diversity scores were better for the plant-based diet, but not so fast! Diversity scores were similar across both groups after four days of being on their respective diets. Some people respond well to vegan diets, and others respond well to more carnivore, animal-based diets. But that’s a topic for a whole other article. The moral of the story, changing what we eat changes our gut biome.

As if there needed to be another reason to exercise, those who exercise have greater diversity and an increased number of species associated with positive health outcomes. That goes for all different flavors of exercise. Low-intensity activities such as walking improve gut diversity and general digestive function. Bouts of high-intensity exercise also change your bacteria and help assist the physiology associated with intense exercise, acting as a performance enhancement (5). I say this with caution, as too much exercise (overtraining) can cause a “leaky gut,” thus worsening digestion and increasing your likelihood of autoimmune disease. The key is to find the correct dose of exercise for you.

Ever experienced a stormy night of sleep? Maybe you couldn’t fall asleep, stay asleep, or woke up after 8 hours feeling like you only slept 2. You don’t need a Ph.D. in physiology to know that sleep disturbances aren’t suitable for the gut biome. Not sleeping well already makes us more stressed, less able to regulate our blood sugar, and less able to fight off infection. All of which can be harmful to our gut bugs.

We know that psychiatric conditions such as depression and anxiety are associated with lower gut diversity. It may be difficult for some to understand the microbiome-mental health connection. But the microbiome and the brain participate in bi-directional communication via the Vagus Nerve (the name vagus means “great wonderer, how fitting…). The gut produces compounds that can travel, via the Vagus Nerve, up to the brain and subsequently affect our mood. Ever have that gut felt something wasn’t right? Or one of my favorite statements, ever get nervous and feel ‘butterflies in your stomach?’ That all has to do with our gut bugs communicating with our brain, crazy right!?

Other Tools in the Shed

I’ve seen things in the health space talking about Fecal Microbial Transplants (FMTs), taking the microbes from a healthy person's feces and putting them into someone with the disease, with success in some instances! Then you have probiotics, which have been shown to have tremendous benefits for IBS, mood disorders, and constipation (check out my article on Probiotics if you want to know more about them). These tools are the more “sexy, extra stuff” for improving gut diversity — especially swallowing another person’s poop. They’d be like buying a new piece of gardening equipment when you have “crap” soil and haven’t read a thing about gardening. It should always start with the five foundational pillars of health: nutrition, movement habits, stress management, sleep hygiene, and life purpose. Remember, what’s healthy for the host is beneficial for the microbiome. All you have to do is eat, sleep, move, and think well. Easier said than done.

As always, trust in Your Gut.

Disclaimer: The contents of this article are for educational purposes only and are not intended to diagnose or treat any condition. Only apply the information in this article after first speaking with your doctor.

References

1. Rinninella, E., Raoul, P., Cintoni, M., Franceschi, F., Miggiano, G,…et Mele, M. (2019). What is the Healthy Gut Microbiota Composition? A changing Ecosystem across Age, Environment, Diet, and Diseases. Microorganisms, 7(1): 14. DOI: 10.3390/microorganisms7010014.
2. Guo, R., Chen, L., Xing, C., et Liu, T. (2019). Pain regulation by gut microbiota: molecular mechanisms and therapeutic potential. British Journal of Anesthesia, 123 (5):637–654. DOI: 10.101/j.bja.2019.07.026.
3. Gianchecchi, E., Fierabracci, A. (2019). Recent advances on Microbial Involvement in the Pathogenesis of Autoimmunity. International Journal of Molecular Sciences, 20(2): 283. DOI: 10.3390.ijms20020283
4. David, L., Maurice, C., Carmody, R., Gootenberg, D., Button, J et al. (2014). Diet rapidly and reproducibly alters the human gut microbiome. Nature, 505(7484): 559–563. DOI: 10.1038/nature12820.
5. Monda, V., Villano, I., Messina, A., Valenzano, A., et Esposito, T. (2017). Exercise modifies the gut microbiota with positive health effects. Oxidative Medicine and Cellular Longevity, 2017. DOI: 10.1155/2017/3831972.