Have you ever been so nervous that you had to rush to the bathroom? Gastrointestinal discomfort during moments of high stress is very common. However, the relationship between the brain and the gut doesn’t stop there — information pathways in the body are never one-way, especially when it comes to gut health. In fact, a growing body of research shows that your gut is deeply connected to your brain, and one influences the other in positive and negative ways.
“You probably know that the brain sends messages to the body in order to control movement, behaviors, breathing, and even when and how to digest food,” says Shawn Manske, ND, Assistant Director of Clinical Education for Biocidin Botanicals. “But, what you may not understand is that the gut — or gastrointestinal (GI) tract — communicates back to the brain.”
“Recent studies show that our brain talks to our gut and vice versa,” confirms Mahmoud Ghannoum, PhD, NIH-funded microbiome researcher and co-founder of BIOHM. “We used to think top-down (brain to gut axis). However, we should also start thinking bottom-up (gut to brain axis). In reality, the two opposite directions mutually affect and depend on each
other.” So, what is the gut-brain axis, exactly? To understand this concept, we must first start by explaining the gut microbiome.
What is the gut microbiome?
“Our bodies are host to trillions of microbes that live virtually everywhere, but primarily within our gastrointestinal (GI) tracts,” explains Dr. Manske. Indeed, between 300 and 500 bacterial species and over 100 trillion microbial cells live in the gut. “These ‘bugs,’ known collectively as our microbiome, play a major role in the health of the gut-brain axis. How do they do that? By a) interacting with our immune cells and the cells that line our gut, and b) creating compounds that have whole-body effects — including influencing the brain and mood.”
“When the microbiome is healthy, it has a good balance of good versus bad microbes … If that shifts, the result is dysbiosis.” Dysbiosis is an imbalance of bacteria — you may have too much of one bacterial species, or too little, for example. “Dysbiosis can develop slowly over time as a result of lifestyle and diet, or it can happen quickly — think medications or food poisoning,” Dr. Manske says. What, then, does the microbiome have to do with the communication to the brain? A whole lot, as it turns out.
What is the gut-brain axis?
“The term ‘gut-brain axis’ refers to the two-way communication between the gut microbiome and the brain,” says Dr. Ghannoum. “This communication occurs through neural, inflammatory, and hormonal signaling pathways. The purpose of the [gut-brain axis] is to maintain homeostasis and protect the body against detrimental factors.”
In other words, the gut and the brain “talk” to each other. The trillions of microbes in our gut “talk” to our brain via blood circulation, the gut’s nervous system, and the gut’s immune system. In turn, the brain “talks” to our gut using the same pathways.
What are gut-brain axis disorders?
“Gut-brain axis disorders are a range of distinct disorders … in which the bi-directional communication system [the gut-brain axis] is not functioning properly,” says Alexander Martinez, the CEO and Co-Founder of Intrinsic Medicine. Gut-brain axis disorders include irritable bowel syndrome (IBS) and inflammatory bowel disease. There’s also evidence to suggest that Parkinson’s, autism, and even rheumatoid arthritis are linked to issues with the gut-brain axis.
How can poor gut health contribute to poor mental health?
Clearly, the gut affects the brain. “Recent investigations demonstrate that the gut microbiome is actively involved in processes linked to brain development, physiology, psychology, and behavior,” explains Dr. Ghannoum. “Specifically, the gut microbiome plays a critical role in the regulation of mood, anxiety, and pain.” In addition, Dr. Ghannoum states that the microbiome influences specific brain functions, including signals sent between neurons (brain cells) and the creation of new neurons.
This means that when the health of the GI tract is off, “eventually it affects mood and brain health,” Dr. Ghannoum explains. “Research has shown that dysbiosis [microbiome imbalance] can contribute to the development or continuation of many systemic diseases — including mental health disorders like anxiety and depression. Did you know that the vast majority of serotonin (our feel-good neurotransmitter) in our bodies is produced in the gut? That means that if our GI health is off, it can cause poor mental health. Additionally, certain microbes may produce inflammation, which is a known contributor to anxiety and depression.”
Jacques Jospitre Jr., board certified psychiatrist and co-founder of SohoMD, agrees that gut and mental health are linked. “Poor gut health is a strong risk factor for anxiety, depression and much more,” he says. “Research clearly bears this out. For example, a  study looked at 1,641 people with gastrointestinal problems and found that the vast majority had anxiety. About one quarter also suffered depression. These are levels much higher than for people without digestive problems.
“Additionally, those with celiac disease (an inflammatory condition of the digestive tract due to wheat allergy) are at higher risk for bipolar disorder. People with irritable bowel syndrome are at greater risk for both anxiety and depression. And yes, an unbalanced microbiome will clearly increase the likelihood of mental health problems.”
Dr. Jospitre also noted, “one study recently showed that simply giving a probiotic to rebalance the microbiome greatly reduced the likelihood of once-hospitalized patients being re-hospitalized for a return of symptoms [of acute mania, a symptom of bipolar disorder]. And, for the few who were still hospitalized after taking the probiotic, their stay was found to be much shorter.”
How can you improve gut health at home?
According to Martinez, the first step is to work with your healthcare provider. The next step? Get familiar with the Bristol Stool Form Scale — a chart that classifies stool (a.k.a. pieces of feces) into categories to help you determine the health of your gut. “This is how you can measure your gut health improvement actions through your bowel movements and make sure they are working for your unique biology,” he says. “Generally, type 3-4 stools are ideal ones that are easy to pass.”
After that, look at your fiber intake. “95 percent of people are NOT meeting the dietary fiber recommendations for their age and gender,” Martinez warns. “Dietary fiber from whole plant foods is what feeds our gut microbiome and keeps the gut environment healthy. Once you identify a shortfall in your dietary fiber (many diet tracking apps can help you find this), then you can increase the amount of fruits, vegetables, and whole grains to move closer to your goal. Don’t forget to use the Bristol Stool Form Scale to inform the foods that work for you and those that don’t. Everyone is different.”
What else can you do to improve your gut health? There is no one-size-fits-all approach, but there are additional healthy habits that can help. Here are the best ways to improve the health of your GI tract, according to our experts:
- Get enough sleep. “Sleep helps our body maintain the detoxification pathways and proper movement of our digestive tract,” says Dr. Jospitre.
- Exercise. “Exercise and movement has a positive impact on gut health and the microbiome, in addition to supporting positive mental health,” says Dr. Manske.
- Drink enough water. “Drinking enough water allows hydration, which is important for robust secretion activity of enzymes,” says Dr. Jospitre.
- Reduce stress. “Meditation and psychotherapy are excellent ways to work on stress,” says Dr. Jospitre.
- Eat a diet high in vegetable fibers, whole grains, fish, and healthy oils. “Eating a Mediterranean diet is proven to lower inflammation in the body and keep mental illness at bay,” says Dr. Jospitre.
- Eat fermented foods. “Include fermented foods like sauerkraut, kimchi, and kombucha [in your diet],” says Dr. Manske. “These have all been shown to encourage the growth and diversity of the microbes in the gut and support optimal gut function.”
- Take the right supplements. “Probiotics plays an important role in alleviating depression. They help to serve the critical function of rebalancing the microbiome,” says Dr. Ghannoum. Wondering what kind to get? Dr. Ghannoum recommends multi-strain probiotics, which may provide better benefits than single-strain products.
Meet our expert panel:
Shawn Manske, ND, is the Assistant Director of Clinical Education for Biocidin Botanicals, supporting clinical education, research, and product development.
Mahmoud Ghannoum, PhD, is a microbiologist, NIH-funded researcher at Case Western University, and co-founder of BIOHM. Through his research, Dr. Ghannoum established that fungal organisms constitute an essential part of the microbiome.
Alexander Martinez is the CEO, chairman, and Co-Founder of Intrinsic Medicine — an entrepreneur inspired to make a public health impact informed by his own patient journey.
Jacques Jospitre, Jr. is a board certified psychiatrist and co-founder of SohoMD, a national Teletherapy and Telepsychiatry platform for integrative and personalized mental health care.
This content is not a substitute for professional medical advice or diagnosis. Always consult your physician before pursuing any treatment plan.
This article was updated on November 29, 2022.