Digestion and Mental Health: The Science and Nourishment of the Gut-Brain Connection
Over the past 10 years there has been a volcano 🌋 of research on the connection between the digestive system (or “gut”) and our brain. While there is still so much more research and exploration that needs to be done, there are some interesting tidbits that have come to the surface regarding the Gut-Brain-Axis.
You may have heard about the gut/brain connection in the latest probiotic commercials, from social media ads, or on your containers of yogurt from the store. “Gut Health” has become a buzzword, “healing your gut” is now trendy (and no surprise, a biiiiiiig money maker in the wellness industry), and of course, is now common discourse in diet culture. And it can be dizzying, with all of the available information from a zillion different sources, to tease out the real information and throw away the flim-flam.
So, we’re gonna offer some help. Let’s get into the nitty-gritty, the microscopic, the inner-universe inside of us (Magic School Bus anyone!?), and gather some wisdom around the gut/brain connection (with a few sprinkles of ADHD gut/brain nuggets mixed in)!
WHAT IS THE BUTT GUT- BRAIN AXIS?
When most people think of the gut, they imagine the part of the digestive system that comes after the stomach, and is responsible for, well… poop. But actually, your gut (or gastrointestinal tract) is an incredibly long (average of 30 feet!!!!🪱) internal system that starts at your lips and ends at, well… your butt.
The gut-brain axis goes beyond just the digestive tract. It is a two-way communication network that links the enteric nervous system (the gut: hunger, fullness, and stress) and the central nervous system (the brain: thinking, learning, moving, sensing) through the vagus nerve (also a very cool part of the body worthy of its own entire post). These two systems are constantly talking to one another, sharing information, and reacting to each other’s experiences and needs.
And FUN FACT! More information passes between your brain and your gut than any other body system! In fact, there are more nerve cells in your gut than anywhere else in your body outside of your brain. For this reason, the gut is often referred to as the “second brain”.
So what’s the point of all this gut-brain chatter? By communicating with one another, the brain and the gut can work together to orchestrate a host of responses in the body, including:
- Hunger and satiety cues.
- Food preferences and cravings.
- Food sensitivities and intolerances.
- Gut motility (muscle movements).
- Digestion and Nutrient Metabolism.
- Mood.
- Emotions.
- Behavior.
- Stress levels.
- Pain sensitivity.
- Cognitive function.
- Immunity.
HOW DOES THE GUT- BRAIN AXIS WORK?
The gut-brain axis is incredibly complicated and contains layers upon layers of details and functions. Here are some key components that highlight how the two systems work together.
Enteric Nervous System:
- A complex network of neurons, neurotransmitters, and proteins in the lining of the gastro-intestinal tract.
- Allows the gut to function independently, learn, remember, and keep things moving.
Neurogastroenterology:
- The gut contains 100 million neurons - that’s more than the spinal cord!
- Includes neurotransmitters and hormones that influence mood and help manage anxiety and stress.
Serotonin:
- 95% of the body's serotonin is produced in the gut, and acts as a communicator between the brain and the gut.
- There is a misconception that if you don’t have “a healthy gut” you won’t have enough serotonin for your brain… but the brain actually makes its own serotonin, separate from what is produced in the gut. It turns out, serotonin has essential functions in both the brain AND the gut.
- Microbes in the gut transform the amino acid tryptophan into serotonin and other metabolites, which then regulates serotonin levels in the brain. Cool stuff!
- Imbalance in brain serotonin is linked to a variety of mental health conditions, including depression and ADHD; high serotonin levels in the gut can cause GI issues.
- Feelings of fear and stress can overstimulate the serotonin circuits in the gut, which can lead to diarrhea and indigestion.
- In terms of ADHD, serotonin in the brain is important because it helps regulate things like mood, impulsivity, and decision making, which ADHDers struggle with..
My Gut is Feeling Emotional:
- The gut is often referred to when describing emotions, reflecting the emotional states from the brain.
- “I have a gut-feeling” - intuition
- “I have butterflies in my stomach” - nervousness, excitement
- “I’m feeling down in the dumps” - sadness, depression, blah-ness
- “That was gut-wrenching” - sadness, distress
- “My stomach is in knots” - anxiety, anticipation
- “There is a pit in my stomach” - anxiety, unease
"Vitamin P" – Pleasure and Nutrient Metabolism:
- CCK (Cholecystokinin): produced in response to protein or fat in meals, but is inhibited by stress, fear, and negative perceptions of an eating experience.
- Aids digestion, reduces appetite, and creates feelings of pleasure in the brain.
- Contrary to the diet-culture messaging that pleasurable food leads to “out of control” eating, CCK helps signal fullness in the brain, and provides feelings of satisfaction that promote intuitive eating.
- In fact, engaging in restrictive behaviors like dieting, can reduce the production of CCK which inhibits digestion and absorption of nutrients, and leaves the body feeling hungry and unsatisfied.
Neuropeptide Y:
- Signals the search for food when pleasure from eating is absent.
- Naturally elevated in the morning or when deprived of food.
- Increases when blood sugar is low, signaling the consumption of carbohydrates.
Blood-Brain Barrier:
- More of a filter than a barrier - it’s job is to let some things in to, and keep other things out of the central nervous system.
- The compounds and byproducts metabolized and created by the microbiome play a role in the production and transmission of neurotransmitters.
- Certain byproducts from our microbiome, such as the essential amino acids phenylalanine (a precursor to dopamine creation) and tryptophan (precursor to serotonin creation), are absorbed in the gut and have the ability to cross the blood-brain barrier for dopamine creation.
Quick Tangent: DOES THE GUT- BRAIN AXIS PLAY A ROLE IN ADHD?
The short answer: “Maybe? Yes? We don’t really know”.
Disclaimer for all things new-research: take findings with a grain of salt. Due to factors like the infancy of this research topic, the limited populations that have been studied and tested, and the unique bodily qualities of all individuals, the following findings are all suggestions, theories, and indications for further research (vs. cold, hard, facts). Take this data in with a lens of curiosity, new learning, and an open mind, and remember that there is NO quick-fix bacteria pill (i.e. probiotic) that will make ADHD symptoms disappear.
A very preliminary, small research study (Aarts, 2017) on the Gut-Brain Axis and ADHD suggests that:
- People with ADHD may have different varieties and amounts of gut bacteria, specifically increased levels of *bifidobacterium*.
- *Bifidobacterium* is linked to higher production of phenylalanine, an amino acid important for making dopamine and noradrenaline, which are key brain chemicals.
- These microbiome differences might affect dopamine-related pathways, possibly leading to less reward anticipation, a common ADHD symptom.
- This study opens the door for continued research on how the gut-brain-axis and ADHD.
TIPS AND TOOLS TO HELP YOU TAKE CARE OF YOUR GUT-BRAIN AXIS
When it comes to supporting your gut (in order to also support your brain), there are 2 helpful food needs to lean into: VARIETY and GENTLE NUTRITION. *It is important to remember that tending to these two “higher level” food needs is very difficult if we are not meeting the food needs that are lower in the pyramid, like regularity and adequacy.*
Here are some ways that you can, or might already, support the bacteria party in your gut (and therefore your brain):
PREBIOTICS / SOLUBLE FIBER
The lively and vibrant community of bacteria in your gut eat and ferment some of the fiber that you consume and can’t digest/absorb on your own. All prebiotics are fiber, but not all fiber is prebiotic.
SOLUBLE FIBER (prebiotic) can be broken down in your gut, thanks to bacteria, but insoluble fiber (not a prebiotic) cannot be broken down and instead works to push everything through the intestine and acts as a scrub brush to keep things looking clean and shiny 🧼(also an important job).
As soluble fiber makes its way through your gut into your large intestine (the home of over 7 billion microbes🦠) it is fermented by bacteria which produces beneficial byproducts that support the processes mentioned earlier in this post.
Long story short: the food source for the bugs in your gut comes from the easy to digest fibers that you eat.
👉🏼 Some examples of foods that provide prebiotics (i.e. food for the bacteria in your gut) include: bananas, oatmeal, asparagus, onions, beans, peas, and SO MANY MORE PLANTS.
PROBIOTICS
Probiotics are the live bacteria in fermented foods, and there are a variety of bacterial strains in different foods. The more variety of fermented foods that you eat, the more variety of bacteria that will end up in your gut.
Adding probiotics into your diet can support digestion and the creation of beneficial byproducts from your microbiome. So, while prebiotics feed the bacteria, probiotics are the actual bacteria that populate your gut.
👉🏼 Some examples of foods that provide probiotics include pickles, yogurt, kombucha, kimchi, sauerkraut, parmesan cheese, kefir
In terms of supplements, here are a few quick pointers:
1) More variety means more diversity in your gut, so look for 2 or more strains of bacteria on the label
2) Check the label to see if the supplement needs to be kept cold in order to keep the bacteria alive (and if so, make sure it’s being kept cold).
🦠Scroll to the bottom of this post for some probiotic supplement recommendations or browse our favorites here. *always consult with your provider before taking any new supplements or herbs*
🦠Double Whammy: the Prebiotic + Probiotic gummy by Llama Naturals is a great option for giving your gut some quick and easy love! And, if you use the code THEADHDRD at checkout, you can save 20% off your entire order!!
BE KIND TO YOUR MIND
Stress releases cortisol which impacts the gut by slowing digestion, irritating the lining, and altering the makeup of those bacterial buddies.
You can soothe your nervous system by activating the vagus nerve (that cool part of the body that connects your gut and your brain). Here is a simple breathing exercise that you can do nearly anywhere, and almost anytime:
👉🏼 Want more tips to be kind in your mind? Check out our blog post: “Moving Towards being more KIND in our Mind”
WORK TOWARDS BETTER SLEEP
When you are asleep, your body is in “rest and digest” mode. When you are resting and digesting, your bacteria are doing their thing. Additionally, lack of sleep has been found to be correlated with lower microbiome composition and diversity. And it can be HARD to prioritize sleep… and annoying to be told “just go to bed earlier”. Instead, here are some of our favorite tips and tools for promoting more and/or better sleep:
- Take a baby step - aim for 15 minutes of extra sleep this week and if that goes well, add another 15 next week.
- Get a pair of quality earplugs (we love Loops!), and/or a soft pillowy eye mask.
- Limit caffeine intake later in the day.
- Do a guided meditation, try out the vagus nerve breath exercise from above, or use a biofeedback tool like MoonBird to relax your nervous system before bed.
- Bring down your core body temperature at night with a cool shower, or turn down the thermostat a few degrees.
- Use an old-school alarm clock so you can leave your phone out of the bedroom.
ENJOY YOUR FOOD
Your digestive system actually does a better job of breaking down and absorbing nutrients when you choose foods that bring you joy, provide pleasure, and stimulate satisfaction. Experiencing guilt, fear, anxiety, or shame about food choices (ahem… lookin at YOU, Diet Culture) can alter the metabolic process, which can then reduce the nutritional value that you get from the food you eat. You can read more about why pleasure is an important part of eating in another post we wrote, here!
TL;DR FINAL THOUGHTS
The gut-brain axis, or connection between our gut and our brain is a fascinating topic, with layers of complexity, new insights and understandings, and intricacies that we still can’t explain or don’t even know about yet! This communication network influences many aspects of our health, including mood, cognition, immune function, nutrient absorption, and recent findings suggest that it might even play a role in ADHD symptoms.
While the research is still evolving, what we do know is that the 2 separate systems - the brain and the gastrointestinal tracts - aren’t actually all that separate. They work together to support one another equally. When one is impacted, so is the other. When one is tended to, so is the other.
And, there are plenty of small ways for you to take care of your gut-brain axis, like including some soluble fiber in your diet, incorporating fermented foods or taking a probiotic supplement, working on stress reduction, increasing self-compassion, and caring for your overall mental health, getting enough quality sleep, and saying "F you" to diet culture by eating foods that provide pleasure!!!
Probiotic Supplements:
Check out my probiotic recommendations on Fullscript below!
https://us.fullscript.com/plans/astorch-probiotic-recommendations
References
Holzer P. (2022). Gut Signals and Gut Feelings: Science at the Interface of Data and Beliefs. Frontiers in behavioral neuroscience, 16, 929332. https://doi.org/10.3389/fnbeh.2022.929332
Fredell, E. (2023, January 18). Gut microbiome communication: The gut-organ axis. American Society for Microbiology. https://asm.org/articles/2023/january/gut-microbiome-communication-the-gut-organ-axis
Cleveland Clinic. (n.d.). The gut-brain connection. Cleveland Clinic. Retrieved August 19, 2024, from https://my.clevelandclinic.org/health/body/the-gut-brain-connection