Ever heard of the Egyptian Plover? Well, in case you haven’t – this bird (also known as the “Crocodile Bird”) has a pretty interesting relationship with its namesake, the crocodile. According to some accounts, the croc’ will allow the bird to fly into its mouth and feed on decaying meat lodged between its teeth. [1] Sounds like a booby trap to me, but the bird doesn’t become lunch. Instead, the crocodile gets its teeth cleaned and avoids rotten chompers, while the bird gets a decent meal in an environment where it has little worry about predators. This is an example of mutualism, a type of symbiotic relationship in which both parties benefit.
Another perfect example of this selfless symbiosis, is that between you and your microbiome – that microbial ecosystem existing in your entrails. In an earlier article, we defined the delicate balance between human and microorganism, even going so far as to announce some noteworthy feeding habits that would benefit your microbiota the best. But in this article, I’d like to focus on that line of communication between your brain and your gut, and how integral they are in impacting your daily decisions.
The “cross-talk” between your gut and brain was appropriately described by Dr. Emeran Mayer, Director of the Center for Neurovisceral Sciences & Women’s Health at UCLA in a 2015 presentation called The Microbiome, Mind & Brain Interactions, as “The Gut Conectome.” This two-way communication occurs over multiple pathways and is known to regulate emotions, pain, eating behavior, stress responsiveness and social interactions. It’s a robust network of cups and strings, linking 100+ trillion microbes to 50+ million neurons. The largest collection of immune and endocrine cells in your body are found in your gut. These, along with a specialized set of [enteric] nervous cells, are perfectly poised to correspond between flora and fruition.
Let’s simplify that a bit. Your brain is directly connected to your gut via neural, physical, chemical and hormonal highways. It’s one way your body senses its environment – not only through the food that you eat, but by listening to what the bacteria in your bowels have to say about it. Ever here of the term, “comfort food?” Ever notice how your mood can swing simply from eating select foods? Well, there’s certainly a chemical connection between food and feelings, but not all of that comes from the “sugar rush” one gets after eating a Snickers. It seems that it may be more about microbial manipulation than anything else.
One study found that by changing the composition of gut flora in mice, researchers could alter the mouse’s behavior. [2] Put in some introverted bacteria and get a mouse that’s less exploratory; expose a shy mouse to extroverted bacteria and it becomes more exploratory. I can here Pfizer’s commercial now, “Have a hard time talking to women? Are you tired of being the boring sap at parties? Then talk to your doctor to see if Gooutandgetthem Bacteriserum is right for you.” Dear goodness! To prove how bacteria could rewire the human brain, scientists conducted a study among three groups of healthy women. For four weeks, they had one group consume yogurt twice per day, another group consumed non-fermented dairy (milk) twice per day, and the third group did not change their diet at all. After the 4 weeks, the group who ate the yogurt had a noticeable reduction in negative reactions to a controlled stimulus. [3] In other words, eating yogurt reduces stress!
And the bacteria have “feelings” just like you! Well, maybe not exactly, but when you’re stressed, they’re stressed. Have you ever noticed that you tend to get sick more often (or more severely) when you’re stressed or tired? That’s due (in part) to your sympathetic nervous system being “in charge.” During that time, your body releases norepinephrine (along with other hormones and neurotransmitters) which increases your heart rate and blood pressure. This chemical signal not only increases restlessness and anxiety in you, but also in the microbiota of the gut. See, not unlike your human cells, bacteria cells also have norepinephrine (NE) receptors, and when they get triggered…look out! Those little critters get hostile! The enteric (intestinal) bacteria flood your gut with even more NE-like chemicals, in a sense “amplifying” the original signal, which alters your biochemistry and overwhelms your own receptors. This action leads to increased permeability of your intestines, which perpetuates the cycle and leads to a sicker human. [4] Signals from bacteria in the gut can also reach the brain directly, passing through (and even altering the permeability of) the blood brain barrier – leading to sickness behavior and depression, and affecting the onset or severity of disease. [5]
Serotonin is another neurotransmitter and, when found in low levels in the body, has been linked to depression and suicide. Alternatively, high levels of serotonin are associated with joyful feelings. [6] Since 90-95% of all your serotonin cells are in your gut, it makes sense that the bacteria inside your intestines may have an influence on serotonin levels. As it turns out, microbes play a key role in regulating serotonin levels. Good bacteria release serotonin, making you feel happy; bad bacteria deplete serotonin levels, making you feel crappy. [7] Researchers have long understood the relationship between negative moods and negative outcomes: showing how hostility can lead to death, while agreeableness protects against mortality. [8] Nice guys may finish last, but that’s because all the bully’s died an early death. I mean, it’s not because they’re bad people…they just sided with the wrong bacteria. The link goes beyond our conscious, and into the “conectome.”
So, next time you have a “gut feeling,” listen – trillions of microorganisms are trying to tell you something; and that “gut reaction” you had was most likely due to the microorganism marionettists playing puppet master. They can control how you feel and fever. Symbiotic microbes can manipulate the brain through the central nervous system, circulatory system and immune system. Not only have they been shown to regulate nutrition and metabolism, they are critical for the development and function of the immune system. [9] Although Western medicine is still trying to get on top of this wave of science, most studies are in agreement that health and well-being of humans starts at the microscopic level. The dialogue between your gut and your brain will continue to take place with or without your input. What is it saying about you?
[1] https://en.wikipedia.org/wiki/Egyptian_plover
[2] https://www.ncbi.nlm.nih.gov/pubmed/21683077
[3] https://www.ncbi.nlm.nih.gov/pubmed/23474283
[4], [9] https://www.ncbi.nlm.nih.gov/pubmed/19404271
[5] https://www.ncbi.nlm.nih.gov/pubmed/25974299
[6], [8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2077351/
[7] https://www.ncbi.nlm.nih.gov/pubmed/25860609
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