Have you ever been so nervous that you had to rush to the bathroom? Gastrointestinal discomfort during times of high stress is very common. However, the relationship between the brain and the gut doesn’t end there – the 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 ways. and negative ways.
“You probably know that the brain sends messages to the body to control movement, behavior, breathing, and even when and how to digest food,” says Shawn Manske, ND, associate director of clinical training for Biocidin Botanicals. “But what you might not understand is that the gut – or the gastrointestinal (GI) tract – communicates with the brain.”
“Recent studies show that our brain talks to our gut and vice versa,” confirms Mahmoud Ghannoum, a microbiologist and NIH-funded researcher at Case Western University. “We used to think top-down (gut-brain axis). However, we should also start thinking bottom-up (gut-brain axis). In reality, the two opposite directions affect each other and depend on each other.
So what is the gut-brain axis, exactly? To understand this concept, we must first begin by explaining the gut microbiome.
What is the gut microbiome?
“Our bodies are home to trillions of microbes that live virtually everywhere, but primarily in our gastrointestinal (GI) tracts,” says Dr. Manske. In fact, between 300 and 500 bacterial species and more than 100 trillion microbial cells live in the intestine. “These ‘insects’, known collectively as our microbiome, play a major role in the health of the gut-brain axis. How do they do this? By a) interacting with our immune cells and the cells that line our gut, and b) creating compounds that have effects throughout the body, including influencing the brain and mood.”
“When the microbiome is healthy, it has a good balance of good and bad microbes…If that changes, the result is dysbiosis.” Dysbiosis is an imbalance of bacteria – you can have too much of a bacterial species, or too little, for example. “Dysbiosis can develop slowly over time due to lifestyle and diet, or it can happen quickly – think of medications or food poisoning,” says Dr. Manske. So what does the microbiome have to do with communicating with the brain? A 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 [gut-brain axis] is to maintain homeostasis and protect the body from harmful factors.”
In other words, the intestine and the brain “talk to each other”. The trillions of microbes in our gut “talk” to our brain via the blood circulation, the nervous system of the intestine and the immune system of the intestine. In turn, the brain “talks” to our gut using the same pathways.
What are gut-brain axis disorders?
“Disorders of the gut-brain axis are a range of distinct disorders … in which the two-way communication system [the gut-brain axis] doesn’t work properly,” says Alexander Martinez, CEO and co-founder of Intrinsic Medicine. Disorders of the gut-brain axis include irritable bowel syndrome (IBS) and inflammatory bowel disease. There is also evidence to suggest that Parkinson’s, autismand even rheumatoid arthritis are linked to problems with the gut-brain axis.
How can poor gut health contribute to poor mental health?
Obviously, the gut affects the brain. “Recent investigations demonstrate that the gut microbiome is actively involved in processes related to brain development, physiology, psychology, and behavior,” says Dr. Ghannoum. “Specifically, the gut microbiome plays a critical role in regulating mood, anxiety, and pain.” Additionally, Dr. Ghannoum claims that the microbiome influences specific brain functions, including the signals sent between neurons (brain cells) and the creation of new neurons.
This means that when the health of the gastrointestinal tract is poor, “it ends up affecting mood and brain health,” says Dr. Ghannoum. “Research has shown that dysbiosis [microbiome imbalance] may 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 body is produced in the intestine? This means that if our gastrointestinal health is poor, it can lead to poor mental health. Additionally, certain microbes can produce inflammation, which is a known contributor to anxiety and depression.”
Jacques Jospitre Jr., certified psychiatrist and co-founder of Soho MD, agrees that gut and mental health are linked. “Poor gut health is a significant risk factor for anxiety, depression and more,” he says. “Research clearly confirms this. For example, a  study looked at 1,641 people with gastrointestinal issues and found that the vast majority suffered from anxiety. About a quarter also suffered from depression. These are much higher levels than for people without digestive problems.
“Furthermore, those who have celiac disease (an inflammatory condition of the digestive tract due to wheat allergy) are higher risk for bipolar disorder. People with irritable bowel syndrome are increased risk of anxiety and depression. And yes, an imbalanced microbiome will clearly increase the likelihood of mental health issues.”
Dr. Jospitre also noted: “a study recently showed that simply giving a probiotic to rebalance the microbiome significantly reduced the likelihood of patients hospitalized once being rehospitalized 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 turned out 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? Familiarize yourself with the Bristol Stool Form Scale – a chart that classifies stool (i.e. pieces of feces) into categories to help you determine your gut health. “That’s how you can measure your gut health-improving actions through your stool and make sure it’s working for your unique biology,” he says. “Generally, type 3-4 saddles are ideal and easy to pass.”
After that, watch your fiber intake. “95% of people do NOT meet dietary fiber recommendations for their age and gender,” warns Martinez. “Dietary fiber from whole plant foods is what nourishes our gut microbiome and keeps the gut environment healthy. Once you’ve identified a lack of dietary fiber (many diet-tracking apps can help you find it), you can increase the amount of fruits, vegetables, and whole grains to get closer to your goal. Don’t forget to use the Bristol Stool Form Scale to track which foods work for you and which don’t. Everyone is different.”
What else can you do to improve your gut health? There’s no one-size-fits-all approach, but there are other healthy habits that can help. Here are the best ways to improve the health of your digestive tract, according to our experts:
Get enough sleep. “Sleep helps our body maintain detoxification pathways and the proper movement of our digestive tract,” says Dr. Jospitre.
Exercise. “Exercise and movement positively impact gut health and microbiome, in addition to supporting positive mental health,” says Dr. Manske.
Drink enough water. “Drinking enough water allows for hydration, which is important for robust enzyme secretory activity,” says Dr. Jospitre.
Reduce stress. “Meditation and psychotherapy are great ways to work on stress,” says Dr. Jospitre.
Eat a diet rich in plant fiber, whole grains, fish and healthy oils. “A Mediterranean diet has been proven to reduce inflammation in the body and ward off mental illness,” 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 microbes in the gut and support optimal bowel function.”
Take the right supplements. “Probiotics play an important role in relieving depression. They help perform the essential function of rebalancing the microbiome,” says Dr. Ghannoum. Wondering which type to choose? Dr. Ghannoum recommends multi-strain probiotics, which may provide better benefits than single-strain products.
Meet our panel of experts:
Shawn Manske, ND, is the Associate Director of Clinical Education for Biocidin Botanicals, supporting clinical education, research and product development.
Mahmoud Ghannoum, PhD, is a microbiologist and NIH-funded researcher at Case Western University. Through his research, Dr. Ghannoum has established that fungal organisms are an essential part of the microbiome.
Alexandre Martinez is the CEO, President and Co-Founder of Intrinsic Medicine – an entrepreneur inspired to impact public health 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 doctor before proceeding with any treatment plan.