The Gut-Brain Connection, Explained

Julia Malacoff
Medically Reviewed
December 5, 2019

You may have heard that you can improve your mental health via diet, and that less stress could soothe digestive issues. But is there really a link between gut health and mental health?

With the growing popularity of probiotics , fermented foods, and even microbiome testing, you’re probably familiar with the idea of gut health . We know that gut health is linked to a host of other health concerns, but one of the most fascinating relationships between the gut and overall health is this gut-brain connection.

While it might sound a little far-fetched at first, there’s actually quite a bit of scientific evidence that our digestive systems and our nervous systems are deeply connected. Here’s what you need to know in order to take advantage of this link for better mental and digestive health.

How do we know there is a gut-brain connection?

“There’s a lot of connection between how we feel emotionally and how that manifests in our body physically, and one of those manifestations is through our gut,” explains Harika Pal , MD, a board-certified family medicine physician at Parsley Health New York . Pal says there’s a very simple way to understand what the “gut-brain connection” feels like in your own body: You know how when you feel nervous, you get that feeling of butterflies in your stomach? That’s a classic example of the gut-brain connection at work.

But the connection goes much deeper than the occasional “gut feeling.” There are actually several pathways of connection from our brains to our guts.

So, how are the gut and brain connected? First, there’s the gut microbiome, an extensive ecosystem of bacteria and fungi housed in your digestive tract. “A lot of communication happens through our gut microbiome, and it can affect the kinds of neurotransmitters we make in our digestive tract, which have a direct impact on our brain,” Pal says.

Likewise, neurotransmitters can also be released in the reverse direction, from the brain to the gut. “And that’s why things like anxiety can cause an upset stomach or can cause diarrhea,” Pal says.

Scientists have long theorized that the bacteria in our gut may be related to a host of mental health issues and even neurodegenerative diseases like Parkinson’s and Alzheimer’s. And now, they’re actually beginning to pinpoint the specific types of bacteria (or lack thereof) that may be associated with these conditions.

For example, a study published in Nature Microbiology this year looked at the microbiomes of two groups of over 1,000 people. In the first group, made up of Belgian participants, researchers found that those who had depression (or who had scored low on a quality of life survey) were more likely to be missing two specific types of bacteria in their guts: Coprococcus and Dialister.

When the researchers looked at the second group, made up of Dutch participants, they found that the same bacteria were missing from those who were depressed, but not from those who had a high quality of life. The researchers aren’t sure whether the missing bacteria is a cause or effect of depression, but the study emphasized the link between gut health and mental health.

What’s more, many mental illnesses, such as depression, are associated with digestive diseases, like Crohn’s and irritable bowel syndrome. A recent study in BMJ Gut even showed that people with depression were more likely to be at risk for irritable bowel disease (IBD).

But that’s not all—there are a couple of other ways the gut-brain connection plays out that we’re just beginning to understand.

More evidence of the gut-brain axis

The enteric nervous system, which is almost like an independent nervous system for the digestive tract, has a direct connection to your brain, Pal explains. There’s also the vagus nerve , the longest of the 12 cranial nerves that help connect the brain with the torso, which serves as the nerve link between the brain and the digestive system.

Recent research in Cell demonstrated this link between gut health and mental health by showing that the enteric nervous system and the vagus nerve likely work together to communicate with the brain. Enteroendocrine cells line our digestive tracts, and are part of the enteric nervous system. They also release hunger and satiation hormones that make their way to our brains via our bloodstream. But scientists noticed that they looked a lot like regular nervous system cells, too.

Turns out, these cells can signal vagal neurons almost instantaneously, stimulating the vagus nerve. In the study, researchers found that when they stimulated the vagal sensory neurons in the gut of mice, dopamine, a “feel good” hormone, was released. This may partially explain why vagus nerve stimulation seems to help people with depression, and maybe even why eating makes us feel so good.

Using the gut-brain connection to soothe digestion

If you’re struggling with digestive issues, taking advantage of the gut-brain connection may be a key part of your treatment plan. “Working on reducing anxiety and stress helps us improve our digestion, especially if you’re somebody who suffers from irritable bowel syndrome or IBD,” Pal says. Even if you don’t have a specific disorder but are dealing with diarrhea, constipation, or irregular bowel movements, stress management can help.

When you’re stressed, your sympathetic nervous system is activated, which actually inhibits GI function muscularly and through mucous secretion and blood flow. To thwart this, Pal specifically recommends mindfulness-based practices, like meditation . “Meditation helps us activate what’s known as our parasympathetic nervous system (PNS), or our rest, digestion, and healing nervous system.” Because the vagus nerve controls the digestive system, and is controlled by the PNS, practices that calm the PNS can help soothe digestive symptoms.

Another strategy that may help is slowing down while you eat. “Really sit down to eat, that way you’re already in a rest-digest state,” Pal suggests. “Take a couple of big deep belly breaths before eating, which can help to activate the vagus nerve to help improve digestion. Digesting our food really well is where we get all of our nutrition, and having the right nutrients in the body is really important for long-term health.”

Can your diet affect the gut-brain connection?

Just like the communication between your gut and brain work in both directions, so do the potential benefits of taking advantage of this connection.

“Improving digestion can help us with our mood,” Pal says. The first step here is to eat the right foods. “A whole foods, plant-based diet that reduces inflammatory foods can be really helpful,” Pal explains. For example, removing sugar , dairy , and simple carbohydrates can make a difference because they can actually feed the bad bacteria in your gut.

“Research shows that gut microbiome composition can help us with our mood, meaning we have the right balance between good bacteria and bad bacteria in our digestive tract.” The best way to achieve that balance, Pal says, is by feeding this gut-brain connection through our diet. We can do this by eating a diverse variety of vegetables and getting lots of fiber , which helps to feed all sorts of species of good bacteria. “Fermented foods also help us increase our gut microbiome diversity,” she adds. For example, incorporating kimchi, sauerkraut, and tempeh may have a positive effect.

Lastly, taking probiotics may be helpful. “There are a lot of studies that show different species of probiotic bacteria can definitely be helpful for both digestion and your mood,” Pal notes. If you’re interested in this approach, check in with a health care practitioner who is well-versed in gut health to find out the best strains and dosage for your specific needs.

Julia Malacoff

Julia Malacoff is an Amsterdam-based freelance writer, editor, and certified personal trainer. She covers a wide range of wellness topics including nutrition, fitness, specific health conditions, and the latest scientific research in these field. Julia graduated from Wellesley College and she works with brands like Shape, Cosmopolitan, Fast Company, Precision Nutrition, Equinox, and Aveeno. Outside of work, you can find her walking her dog, trying out a new recipe, or learning Dutch.

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