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  This Is Your Brain on Gut Health (And Vice Versa)
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This Is Your Brain on Gut Health (And Vice Versa)

After a fall left her with permanent brain damage in 2015, Brooke Knisley’s journey back to health started in the gut

Brooke Knisley

Your brain controls everything—people forget that. At least, I know I did before I fell over 20 feet out of a redwood tree in 2015. I didn’t break a single bone in my body but ended up permanently disabled, and began having the worst digestive issues imaginable. This last bit may seem arbitrary but, according to some experts, makes perfect sense.

The brain-gut axis consists of a complex network involving neuroendocrine and immunological signaling pathways and bi-directional neural mechanisms. Importantly, modifying the gut microbiome alters this axis,” says a 2021 article published by Current Neuropharmacology.

In essence, a troubled mind can create a troubled gut which, in turn, can contribute to the troubled mind creating a feedback loop of (yep, you guessed it) trouble. What does that mean for you? Well, maybe your depression and anxiety are caused by different stimuli than you previously thought—or maybe your digestive issues require a more cognitive-based approach.

Your Second Control Center

“The small intestine is where a majority of our neurotransmitters or mood-regulating hormones are,” explains naturopathic doctor and epigenetic intuitive Dr. Melanie Keller, “and also where our nutrition is absorbed. So if you have an overgrowth of bacteria in that small intestine, where all of that work is getting done, then you can have nutritional deficiencies which can contribute to mental health.”

Let me give you an example.

When I fell out of that tree and hit my head on two branches and then the ground, I suffered a diffuse-axonal injury. That’s doctor-speak for a closed-head injury where my brain ricocheted off the sides of my skull and caused damage to parts of itself that would usually only be damaged in open head injuries (that result in … death). My brain stem, which controls automatic functions like digestion, took some damage during this shake up. You see where I’m going with this?

A Feedback Loop of Misery

But my brain was swelling. Like when you knock your arm and blood rushes there to form a bruise, I had excess fluid in my skull that needed to be released. For this, they put a bolt in my head to relieve pressure on my brain. But when you have a literal hole in your head, they pump you full of antibiotics to make sure you don’t end up with a brain infection. When your gastro-intestinal tract is already having a hard time, antibiotics do a number on it, especially when not balanced with probiotics (which feed the good bacteria and prevent complete decimation by the antibiotics).

For me, the antibiotics killed off a lot of the good gut bacteria I had and let one strain grow out of control, causing a highly contagious and incredibly painful large intestine infection called Clostridioides difficile, or C. diff. You might have heard of it.

“For others, if they have this small intestinal bacterial overgrowth, it can actually feed the bacteria,” says Dr. Keller. “And here's the caveat: These are not bad bacteria. These are bacteria that are good guys—probiotics when they're in the large intestine. This is just a situation of gut motility.”

And although your brain is the command center of the body, it receives messages, too. Contrary to some beliefs, one’s body isn’t a dictatorship. In fact, Dr. Inna Lukyanovsky says researchers are working on improving the messages the gut sends to the brain. “For the microbiome, they’re working on things called psychobiotics: Probiotics that have been studied to improve anxiety, to improve memory, to improve mental wellness.”

So what happens when those messages aren’t improved? Remember, a troubled intestine can send signals to the brain—a toxic SOS, if you will. My situation is a great example of this. As serious and traumatic as my head injury was, it was only when the C. diff began ravaging the lower half of my body (through what felt like acid diarrhea), depleting my nutritional intake, that my morale took a nosedive. Thanks, neurotransmitters.

A 2021 study published by the Immune Network further supports this. “The gut closely connects with the central nervous system through dynamic, bidirectional communication along the gut-brain axis. The connection between gut environment and brain may affect host mood and behaviors.”

Read more: How Does Alcohol Impact Sleep?

Psychotherapy for Your Gut Brain

You may be thinking, “This information is disgusting and interesting, but what can I do about it? Tell us something hopeful.” Well, you have control. But it’s going to take hard work, and it’s not enough to simply change your diet.

A notable study published by Front Psychiatry in 2020 found those with irritable bowel syndrome saw a significant improvement when treated with psychotherapeutic interventions. “The World Gastroenterology Organization states that CBT, hypnotherapy and psychodynamic therapy are more effective in improving global symptoms than usual care.”

So yes, you should consider therapy—the psychological kind. 

Two years after my accident, I started psychotherapy for my depression, stress and other comorbidities. I began eliminating certain foods from my diet before slowly reintroducing them, to see which ones exacerbated my terrible bowel movements. Six years post-fall, I’m now vegan, drink an ample amount of kombucha and still see my psychotherapist every week. My digestion has finally normalized a bit, although I do have flares—it’s the nature of living with a traumatic brain injury, unfortunately. But this is the best I’ve felt in six years.

In conjunction with this, Dr. Lukyanovsky recommends we diversify the microbiome. “Don’t throw in probiotics right away. Start with very small amounts of fiber to start improving the microbiome and regrowing and diversifying.”

And Dr. Keller agrees. “It’s a ‘Goldilocks’ situation,” she explains. “Probiotics are very powerful. Some people will think that because they don't have a gut problem, they don't associate their lack of energy, or their insomnia, or their short temper to the probiotic.”

I’ve found kombucha works, but sauerkraut wrecks me. Everyone’s gut biome—and brain—is unique. Find what works for you and make a therapy appointment. Your intestines will thank you.

“Not all medicine is for all,” quips Dr. Lukyanovsky. “Incorporate tools to get your mind and body in sync. If you're only working with someone on the physical end, it might not work. One cannot heal without the other.”

Brooke Knisley is an Oceanside, CA-based comedian seeking representation for her traumatic brain injury memoir. Find her at or on Twitter.

Header image by Priyanka Singh via Unsplash.

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