Explainers Food and Mood

What’s your intestinal flora? Why care about the gut?

January 25, 2018

Kurzgesagt (In a nutshell)

  • Your microbiome is all the bacteria that live on our surface and within our bodies. They are pretty numerous, your intestinal flora alone (the bacteria in your gut), weighs about 4.5 pounds.
  • Many gut bacteria are actually beneficial, helping with digestion, training the immune system, reducing inflammation (oh, and they may help determine whether or not you’re fat)
  • The gut and the brain are connected through an information superhighway (aka nerve) called the vagus nerve, this nerve might help the gut transport information to our brains which influences our actions  
  • Want to learn what you can do to improve the health of your intestinal flora? Read more here

What is your microbiome?

Your microbiome is the bacteria that lives on our outer surface and within our bodies. It’s comprised of organisms including, bacteria, yeasts, fungi, viruses and protozoans. Your intestinal flora alone (the bacteria in your gut), weighs about 4.5 pounds, heavier than your brain, and contains trillions of bacteria. Oh, and if you weren’t cringing a little bit already, a gram of shit, contains more bacteria than there are people on earth.

That lovely little introduction might be make you want to hurl, especially if you’ve grown up in a western home, with a neat freak mom (sorry, I’m projecting) who waged a constant war on all unknowable bacteria. Apparently, our deep-seated fear of bacteria was born from the tuberculosis epidemic, when people were taught the value of cleanliness to try and quell the rampant spread of the disease. Since then, many of us have thought of all unknowable organisms as invisible, little evil invaders, who target the old and young alike. Infecting us, making us sick and sometimes even killing us. While this can sometimes be true, more often than not, bacteria is benign or even helpful.

What’s happening with your intestinal flora? More importantly, why should you care?

Why care about intestinal flora?About 99% of all bacteria on/in your body can be found in the same place, your intestinal flora. Our gut is made up of three kinds of organisms: harmful critters (the ones we all know and fear), chillers who take up space that would otherwise be taken up by bad guys, and the hardworking helpful bacteria. Let’s talk a little more about the beneficial bacteria. Beneficial bacteria in our guts help with digestion, they produce nutrients, digest the indigestible, train the immune system, protect us against food-borne disease, reduce inflammation, and may help determine whether you’re fat or skinny (listening, now, aren’t you). Plus, a variety of other shit (pun intended) I won’t go on to name. Also, susceptibility to a host of different diseases, ranging from mental to physical are beginning to be linked back to bacteria in the gut. Diseases that include obvious things like IBD (inflammatory bowel disease), which science is beginning to show might have a unique microbial signature, but also include some more surprising discoveries like a link with autism.

Our intestinal flora is starting to emerge as science’s new darling, and as scientists begin to study it more, they are starting to come to grips with how little they know. Unfortunately, despite centuries of suspicion that we might be sharing our bodies with trillions of bacteria, we were unable to properly study them until about a decade ago, when new emerging sequencing technologies opened up this world of microbes to study. By 2008, the Human Microbiome Project (HMP) was established, which aimed to categorize and identify the microorganisms associated with both healthy and dead humans. The project closed in 2012 but did contribute to over 190 publications between 2008 and 2012. Anyhoo, since the establishment of that project more and more promising research is being performed.

What happens when you don’t have a microbiome?

Well, we can’t really answer that, at least not in humans, but we can in rats. Obviously, this makes these studies only partly applicable to you. That being said, they are still cool as a motherfucker. In order to figure out what a microbe-free mammal may look like, researchers in Japan bred germ-free mice. Basically, they delivered rats by C-section and placed them in sterile plastic bubbles. The rats could only be handled by researchers with hazmat suits on, and the rats could not be exposed to any outside elements.

These germ-free mice developed a host of issues, including underdeveloped brains and lungs, hyperactivity, anxiety, fear motivated behaviour, impaired learning, increased stress and immune response, and strange social behaviours. Basically, these were weird mice.

Scientists have since introduced germ-free mice to bacteria from “normal” mice, and they began to take on the characteristics of the “normal” mouse, without ever coming into contact with them. Some examples include reduced inflammation, less hyper-activity and more social behaviours. As they introduced different species of bacteria one at a time, or in stages, they have even been able to isolate for the roles that certain bacteria may play in physical and mental health. That being said, in real life, these bacteria don’t exist in a vacuum, and interplay between them and the rest of microbiome will influence their function.

The gut brain connection: they be linked, yo!

Earlier, I mentioned that your intestinal flora might play a role in certain mental disorders, including autism. Your finely (or maybe not so finely) tuned bullshit meter might be beginning to sound as you read this, since I know mine definitely did the first time I started learning about the link between the gut and the brain. I’m happy to report, it’s not bullshit.

Scientists are only beginning to understand the link between the gut and the brain. The gut has its own semi autonomous nervous system, called the ENS (enteric nervous system). This nervous system is capable of functioning, without consulting your brain, and generally does so. Only very important stimuli make it to your brain, via Vagus nerve, otherwise known as the information superhighway that connects your gut and brain. There, the brain’s gatekeeper (the Thalamus) decides if the information is important enough to make it to your brain.

Scientists are starting to discover that the stomach (and intestinal flora) might have a greater role to play in our thoughts, feelings and actions than otherwise thought. It makes sense if you think about it. The brain is basically a king in a castle. It exists, isolated, surrounded by a hardened skull and a membrane, enjoying only filtered blood. The gut is right in the thick of it, where 80% of our immune cells live, it’s subjected to undigested food, bacterial invaders, unfiltered hormones and a host of other stressors. The gut is on the front lines. The brain is the command center. It’s vital that the command center understands and reacts to what’s happening on the front lines.

Scientists are also beginning to discover some curious things, which support the hypothesis that our guts influence our moods. For one thing, it seems that about 90% of the serotonin (a neurotransmitter that influences mood) produced in our bodies are actually produced in our guts. This might be one way our gut (and intestinal flora) communicates with our brains, by producing neurotransmitters. Additionally, scientists have found evidence of the existence of bacteria that stimulate immune cells in the gut, sending a kind of alarm signal to our brains, activating immune cells that help the brain recover from injuries. Plus, new studies are beginning to show that bacteria in our microbiome can actually influence what foods we crave, and ultimately eat.

The wrap up! Actioning it.

Alright, alight, so I just dumped a shit load of information on you. After reading this, you might be wondering to yourself, that’s cool but what in the hell do I do now? Well, before I provide any recommendations at all, I want to remind you, this is a very new field of study. These recommendations are based on the limited evidence available now.

Based on the evidence we have to date, our intestinal flora is influenced by everything from how you are born, what bacteria you’re exposed to, genetics, whether or not you take antibiotics, lifestyle (exercise and eating habits). The first few factors you can’t influence. But the last two are within your control.

Let’s start with antibiotics. Try to limit them whenever possible. I am not saying refuse them at all costs. If you have pneumonia and you’re doctor prescribes them, take them.  It’s better than risking death. Rather, if you have a cold, just man up and let your body fight it off. You’re immune system is equipped, plus if it’s viral, antibiotics won’t do shit for you anyways.

Now, lifestyle, try to exercise regularly. Evidence is beginning to show that regular exercise promotes healthy digestive flora (and healthy everything). Eat soluble fibre, helpful gut bacteria like it. They gobble that shit up, and break it down into nutrients and grow mighty and numerous. Stay away from that high-fat, high-sugar western diet that many of us (including me) know and love. This reduces the diversity of our gut bacteria, which is bad af.

To wrap this essay up, I’ll say: this field of science is extremely new and it appears that the more scientists learn about it, the less they seem to know. That being said, it’s looking extremely promising. It may have far reaching implications on our relationships with germs, the medical community and lifestyle choices. Only time and research will tell, but I am excited to find out.

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