What is the gut-brain axis?

Key Points

• The gut-brain axis is a communication highway between the brain and gut involving the vagus nerve, immune system, digestive system, and more.
• The gut-brain axis may influence mood, gastrointestinal (GI) function, and other neurological functions.
• You can support your gut health through a balanced diet, targeted supplements, and lifestyle modifications.

Have you heard of the gut-brain axis? If you’ve researched gut health, chances are you’ve come across the term. But what is this mysterious “communication highway” between the brain and the digestive system? How does it work? And why should you care about it?

We’re going to explore what the gut-brain axis is and how it influences many facets of health, including digestive issues and mental well-being.

What is the gut-brain axis?

The gut-brain axis (GBA) is a bidirectional communication highway between the brain and the gut, connecting the central and enteric nervous systems. This connection links intestinal function with the cognitive and emotional centers of the brain.

What does that mean, exactly? It means the bacteria and microbes in your gut can influence functions in your brain, such as hunger, mood, and neuromuscular function.

The highway is bidirectional, meaning it goes both ways from gut to brain and brain to gut. The pathway includes the vagus nerve, enteric nervous system, and all the neurotransmitters in the GI tract. It also extends to the endocrine, immune, and hormonal systems.

How does your gut affect your brain?

The gut-brain axis is still being researched, but there are already some well-established ways in which your gut influences your brain.

The most obvious connection between your gut and brain is that this communication system helps maintain gastrointestinal homeostasis and cues your brain when you are hungry, full, or uncomfortable. But the communication goes far beyond just digestion.

Several mood disorders, including anxiety, depression, and autism spectrum disorder, are all linked to functional GI disruptions. Many GI disorders, like irritable bowel syndrome (IBS) or irritable bowel disease (IBD), have been found to dysregulate the enteric nervous system and impact intestinal motility and secretion.

This influence likely exists because neurotransmitters within the GI tract contribute to the creation and modulation of brain neurotransmitters, such as serotonin, histamine, GABA, and acetylcholine, which significantly affect mood, sleep, and overall well-being.

Gut-brain crosstalk might even influence motivation, affect, and higher cognitive functions. So, if you’re feeling unmotivated, take a second look at what’s on your plate!

How the gut-brain connection impacts your health

As mentioned, gut microbiota are believed to influence depression and anxiety, as well as dysbiosis in individuals with autism. In some research, gut disruption was associated with enhanced vulnerability to colitis in concert with depression, as well as changes in colonic motility and intestinal microbial profiles.

This also explains why stress can significantly disrupt the gut. Stress signals from the brain can travel down to the gut and impact microbial diversity, digestion, and more.

IBS is a perfect example of GBA disturbance. This GI disorder is a direct result of a disturbance along the microbiota-gut-brain axis. Signals from gut microbiota result in inflammation, visceral hypersensitivity, and GI symptoms like bloating or gas. It can even lead to mood disturbances like feelings of anxiety or depression.

In IBS, the normal communication between the gut and brain (and all other bodily systems), which typically signals harmony and homeostasis, instead can trigger fluctuations in the enteric nervous system, which includes the muscular and secretory systems of the GI tract. This is how IBS can lead to diarrhea, constipation, and other bowel issues.

What are the symptoms of gut-brain dysfunction?

When it comes to gut-brain dysfunction, you may expect typical gut symptoms like gas, bloating, nausea, and inflammation. While these can occur, other symptoms may include:

• Acid reflux
• Functional dyspepsia (chronic indigestion)
• Slow gastric emptying (gastroparesis)
• Unexplained mood changes
• Unexplained weight changes 
• Hypersensitivity 
• Heartburn 

Prebiotics, probiotics & the gut-brain connection

Probiotics are some of the most well-studied gut supplements. While it’s well-known that they help balance gut microbiota, emerging research highlights how they may influence the gut-brain axis and aid in improving neurological conditions.

Studies suggest certain probiotic strains may positively affect individuals with autism, depression, anxiety, multiple sclerosis, and Alzheimer’s disease. This is incredible news for those struggling with mental health and other challenging conditions.

You can also get consume probiotics in foods like sauerkraut, kimchi, miso, tempeh, yogurt, and more. Probiotic capsules are much more potent than probiotic foods, but everyone is different, so one may work better for you than the other.

Prebiotics are also crucial. These fibers help support the production of “friendly” bacteria in the gut. Prebiotics exist in artichokes, oats, garlic, onions, bananas, and asparagus.

What foods help gut health?

Of course, diet always plays a role. To support gut health, focus on whole foods and minimize processed foods. Processed foods are full of added sugar and fillers that can be difficult to digest and wreak havoc on the gut.

Most Americans don’t have enough variety in their diet, particularly when it comes to fruits and vegetables. Eating a range of produce helps diversify the bacteria in your gut, keeping it healthy. Aim for 30 different types of plant-based foods per week (this includes fruits, vegetables, whole grains, beans, and nuts).

On the other side of things, it’s also helpful to minimize the number of ingredients you’re consuming at one time. Instead of a smoothie with 12 ingredients, for example, where it’s easy to consume a lot of different foods at once, try to keep it around 4-6 ingredients. The same goes for salads with several different toppings or meals with multiple courses.

Polyphenols, which provide antioxidant and antibacterial benefits, are also great for gut health. Polyphenols are found in apples, broccoli, plums, coffee, and certain teas. Learn more about foods for gut health here.

How does your lifestyle affect the gut-brain axis?

Your lifestyle is another factor in your gut health.

Chronic stress can impact colonic motor activity via the GBA, which can lower beneficial bacteria. As mentioned, gut microbes can influence mood, and since the GBA is bi-directional, stress can have the opposite effect on gut microbes.

A sedentary lifestyle isn’t great for your gut, either. Lack of exercise can lead to a lack of gut biodiversity. Research has found that those with obesity have marked changes in their gut microbial population, which could further contribute to adipose (fat) tissue.

A poor diet is another factor in poor gut health. Excess dietary saturated fats may increase pro-inflammatory gut microbes, leading to an imbalanced gut and more inflammation in the body. A diet high in processed food can be tough on the gut with saturated fats, added sugar, and filler ingredients. Try to keep processed snacks to a minimum.

Other factors like smoking or excess alcohol intake also change gut microbiota and can contribute to IBD.

FAQs

How do you heal the gut-brain axis?

Healing occurs in the gut, not in the gut-brain axis. What might be broken is communication between the two, or the microbes in your gut may be out of balance. Other than the lifestyle factors addressed above, different therapies such as cognitive behavioral therapy (CBT), gut-directed relaxation training, or biofeedback may help heal chronic gut dysbiosis.

How does the gut-brain axis affect mood?

The microbes in your gut send different signals to your brain. An imbalanced gut with too much “unfriendly” bacteria or a lack of biodiversity may lead to low mood or unexplained changes in mood.

How does stress affect the gut-brain axis?

Stress can lower the amount of beneficial bacteria in your gut, potentially throwing your gut health out of balance. The gut-brain axis involves both hormonal and neuronal pathways, so changes in either your brain or your gut can throw off both gut health and your mood.

Take control of your gut health

While it may feel overwhelming to take in all this information about how the gut works, the good thing is that there are steps you can take to gain control of your gut health.

The best way to take control of your gut health is by working with a registered dietitian. An RD can assess your current diet and lifestyle to help find ways to improve your gut health and reduce or eliminate your symptoms.

Fay connects you with qualified dietitians covered by your health insurance. This means you could work with a trusted gut dietitian for as little as $0 per session.

Start working with a Fay gut health dietitian today.

The views expressed by authors and contributors of such content are not endorsed or approved by Fay and are intended for informational purposes only. The content is reviewed by Fay only to confirm educational value and audience interest. You are encouraged to discuss any questions that you may have about your health with a healthcare provider.