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  • Writer's pictureJeremy Likness

Gut Check: Parkinson's Disease and the Gut-Brain Connection

Updated: May 3, 2020

This may be a bit much for some of you to stomach, but there is a scientific connection between your brain 🧠 and your gut. If you've ever had a gut-wrenching experience, you know what I mean. Most people are aware that emotions impact your gut. I spent years dealing with butterflies 🦋 before presentations (and as much as I've spoken in public forums, that's a lot of butterflies!) and experienced nausea in my stomach due to anxiety. I've had stomach pain so severe I had to stop to catch my breath after almost being involved in an accident on the interstate. But did you know that the converse is also true? Are you aware that the health of your gut can impact your emotional state and brain health?

A brain and a butterfly
Brains and Butterflies

So how does the brain connect to the butterflies in our stomachs?

The Gut-Brain Axis (GBA)

The gut-brain axis or GBA refers to the connection between the brain and the gut. This includes your stomach and intestines. As this study describes, there is bi-directional communication between the central nervous system (your brain and spine) and the enteric nervous system (your gut). For perspective, although the brain contains an impressive 86 billion neurons (neurons are nerve cells responsible for communication), the nervous system that controls your gut has over 500 million neurons. Although that may not seem like much of a comparison, it makes more sense when you consider what the gut actually produces. The gut, it turns out, is the main culprit behind production of some very important chemicals.


Let me introduce you to my friend, 3,4-dihydroxyphenethylamine.

Dopamine molecule

Dopamine is a neurotransmitter. It is the chemical connection that helps relay messages between neurons. In people with Parkinson's Disease, the neurons that produce dopamine die, resulting in lower dopamine production. This, in turn, means certain signals are either lost or degraded. The result is loss of control and manifests in symptoms like tremors and muscle cramps.

The gut produces 50% of dopamine in the body! The other half is produced by the brain.


Dopamine's close friend is 5-hydroxytryptamine.

5-hydroxytryptamine molecule

Serotonin is also a neurotransmitter. It is well known for its connection to mood. It has multiple functions in the body, ranging from regulating sleep and mood to impacting eating habits and sexual behavior. What many people may not know is that serotonin helps regulate movement in your gut (if you want to impress your friends, it's "gastrointestinal motility"). Here's the kicker: over 90% of the serotonin in your body is found in your gut!

More on these later. Before I dig deeper, I want to cover one last part of the GBA (isn't it cool we're using insider acronyms now?)

Vagus Affects Your Nerves

The last aspect of GBA I want to cover for before moving on is the main nerve that coordinates communication between the brain and your gut: the vagus nerve. One of the longest nerves in our nervous system, it is also referred to as the pneumogastric nerve. The vagus nerve actually branches into a collection of nerves that control various body functions, including digestion. This is the nerve that communicates fight or flight response. When you are nervous, the body shifts resources from "relaxation" such as muscle repair and digestion to increased heart rate and adrenaline to fuel your fight or rapid retreat.

What's interesting is that the communication is bi-directional and the state of your gut can actually affect your state of mind! A quote from this study "shows clearly that the stomach also has a say in how we respond to fear; however, what it says, i.e. precisely what it signals, is not yet clear."

As someone who has been plagued by gut problems for most of my life, I've focused a lot on how to keep my gut healthy. This led to decisions like eliminating dairy and reducing sugar intake, but one piece that keeps coming up in my research is "gut flora." It turns out that our gut is filled with bacteria, and that's not necessarily a bad thing.

The Flora of the Gut

If you want a good conversation starter, bring up "human gastrointestinal microbiota" at your next party. It's a more profound sounding term for "gut flora." We do not fully understand what the role of each species or strain of bacteria is, or even how the bacterial colonies establish themselves in humans in the first place. However, it is clear from research that the presence of certain strains has a major impact on overall health.

In one study, subjects who ingested probiotics containing strains of Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum were less depressed and had better insulin levels. Another study used Lactobacillus helveticus and Bifidobacterium longum to successfully treat anxiety and depression without negative side effects. It is clear that these bacteria are very important for overall good health. Some bacteria even help produce serotonin! (I told you I'd come back to that).

Zoo Keeper

If your stomach is a zoo with exhibits featuring different strains of bacteria, what can you as the "zoo keeper" do to keep them healthy?

👎 Some things destroy the healthy flora in your gut. These include:

  • Antibiotics can kill healthy bacteria and cause harmful bacteria to grow.

  • Obesity, likely due to high fat and high sugar diets, can negatively impact gut flora (see this study).

  • Researchers don't know how, but studies like this one show that artificial sweeteners can reduce the amount of healthy bacteria in your gut. What's worse, other studies show that artificial sweeteners also increase glucose intolerance and can lead to increased risk of diabetes. This is why I don't replace real sugar with artificial sweetener.

  • Simple sugars and fats can reduce healthy bacteria, as evidenced by this study.

👍 What if you want to expand your exhibits? Here's how to encourage healthy bacteria and get rid of the harmful flora:

  • This study also determined that consuming complex carbohydrates helps eliminate harmful bacteria. Take heed, low carb Paleo and ketogenic dieters: skinnier isn't always healthier!

  • A vegetarian diet protects against the growth of harmful bacteria such as E. Coli.

  • Fermented foods like Kimchi, Kombucha, Sauerkraut, Tempeh, and Yogurt help establish healthy bacteria.

  • Probiotic supplements are an effective way to deliver and establish healthy bacteria. The question is "which probiotic" and I'll cover that in my conclusion.

Parkinson's Disease and Gut Health

Although I have always known about the importance of gut flora for overall health, I only recently discovered the role it plays in Parkinson's Disease. For a long time, scientists have been aware that many people experience gut-related symptoms such as constipation, bloating, difficulty swallowing and indigestion long before they manifest other PD-related symptoms. Experiments with mice show that changes in gut bacteria can worsen PD symptoms. Human observations show that people with PD have different gut bacteria compared to people who don't have PD.

Researchers are still trying to understand the link and how it impacts PD. A growing amount of evidence suggests that PD may start in the gut and travel to the brain through the vagus nerve. If so, preventing this migration up the vagus nerve could be key in slowing, halting, and eventually even preventing the spread of PD. To understand how this may happen, you have to meet Lewy.

Lewy, Lewy

Lewy bodies are sticky clumps of protein that abnormally aggregate in nerve cells. They are closely connected to Parkinson's Disease because their numbers increase as the disease progresses. It is not clear if they are a symptom of the disease or a root cause. Lewy bodies are linked to a number of progressive neurological disorders, including PD and Dementia with Lewy Bodies (DLB).

The main protein present in Lewy bodies is alpha-synuclein, often written as α-synuclein. The exact role that α-synuclein plays is not clear. It is present in the tips of neurons and is believed to play a role in releasing neurotransmitters. Now we've come full circle from showing the PD symptoms are due to neurons dying causing a reduction in dopamine, to this key component of neurotransmitters appearing in unnatural clumps. It is not known why the clumps form, but their presence disrupts normal cellular function. They are also present in Alzheimer's Disease and play such a significant role in many neurological diseases that the diseases are classified as synucleinopathies.

Lewy gets on my nerves!

Stop the Alpha Synuclein Aggregation

Some researchers believe that preventing the spread of α-synuclein may slow and event halt the progression of PD. If this is true, there are some very promising studies that suggest it is possible. One study conducted on round worms found that administering the bacterial strain Bacillus subtilis not only halted the progression of α-synuclein aggregation, it actually reversed it by reducing existing aggregation! There's a world of difference between worms and humans, but research like this is certainly very promising in the search for a cure.

I volunteered to participate in an immunotherapy trial that uses the administration of antibodies to stop α-synuclein aggregation. The trial is currently on hold due to COVID-19, but I'm excited to start it after current restrictions are lifted. Fortunately, there are some steps I can take before then ... like taking a probiotic that contains B. subtilis!

Conclusion: Probiotics

I recently published a blog post about my supplements for Parkinson's Disease. A longtime colleague of mine read the post and reached out to me. He suggested looking into a probiotic company that was started by a former Microsoft employee. I checked out the site and was immediately impressed with the science behind their products. The company produces seasonal probiotics that are constantly updated. I ordered the current blend along with a special "starter" and have been taking it for a few weeks now. The two things I've noticed are that the skin on my face is not as dry and I've had fewer episodes of stomach pain. Only time will reveal if I obtain other benefits and how it might impact my PD.

Disclosure: this article contains affiliate links and I may receive commissions. Anything I link to is a product or service I recommend because I've purchased and/or personally verified and used it.

The company is named Jetson. Here's the breakdown of what's in their probiotic:

I'll continue to report back how it's working for me. Right now, I'm feeling great about my gut health and the fight against Lewy bodies.


Jeremy Likness


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