Ever had butterflies in your stomach or a vague feeling of nausea when you knew that something just wasn’t right? It’s no coincidence that the feelings we have in our head often manifest in our gut: they're actually evidence of the gut-brain axis, a theory taking root in modern medicinal practices that shows our gut and our brain are more connected than we previously thought.
While the gut-brain axis has only recently appeared in Western medicine, integrative medicine specialist Dr. Elizabeth Trattner notes that the gut-brain connection is evident in ancient medical practices, such as Traditional Chinese Medicine. In this school of thought, she notes, “Worry, thinking... are all interconnected to digestion.”
Clinical studies are now validating what many people have known all along – albeit often subconsciously: that the gut truly is a “second brain” and acts as a mirror to what is going on in our mind.
How Are the Gut and the Brain Connected?
The gut and the brain are connected in a number of ways.
Physically, the gut and the brain are connected via the vagus nerve, the longest of the cranial nerves. The vagus nerve is responsible for sweating, heart rate, gag reflex, and satiation after eating. But the vagus nerve can also be activated during times of emotional stress. One 2014 study in the Journal of Neuroscience showed the ways in which the vagus nerve is responsible for many of what we have intuitively long called "gut instincts."
Another 2014 study published in PLOS One illustrated an even more direct link between the vagus nerve and the gut-brain axis. In this study, people with IBS or Crohn’s disease were shown to have reduced vagal tone and higher amounts of the stress hormone cortisol in their saliva, indicating a link between their gut symptoms, their stress hormones, and vagus nerve health.
The gut also contains neurons – about 500 million of them – making up what is known as the enteric nervous system: a true second brain.
“Through communication with the brain,” notes Trattner, this nervous system “is reported to play a major role in anxiety, depression and in certain diseases.”
The gut and brain are also connected thanks to the trillions of microbes living in the gut. Many of these microbes produce essential neurotransmitters, like gamma-aminobutryc acid (GABA), which has been proven to help control anxiety and improve sleep.
By taking care of our gut, we promote healthy vagal tone, a healthy enteric nervous system, and healthy microbes, perfect for producing these essential neurotransmitters. But a troubled gut can have adverse effects on mental health.
Perhaps the most well-documented example of this is the link between general inflammation, a problem plaguing many Americans linked in part to an unhealthy diet (and in part to long-term heightened stress), and mental health. Prolonged general inflammation has been found to lead to a number of physical and mental health issues, including cancer, anxiety, metabolic disease, and Alzheimer's.
A troubled brain can also send signals to the gut, causing GI symptoms to manifest as part of anxiety, stress, or depression. Nausea, diarrhea, and loss of appetite are all common physical symptoms of these brain-related issues.
Samoon Ahmad is a psychiatrist who has seen this first-hand with several of his patients, including one gentleman who made an appointment following prolonged GI distress.
“He came to me, not a believer in psychiatry in the first place, to be honest,” says Ahmad. His patient relayed that for the past two years, he had been caring for his mother, who was suffering from Alzheimer’s.
“He was the sole caretaker,” recalls Ahmad. “And that, to me, I think sort of was the straw that broke the camel's back and brought on these GI symptoms."
Seven months after beginning treatment for anxiety, the patient's GI symptoms were cured.
Healing the Gut-Brain Axis
In order to promote a healthy gut-brain axis, doctors recommend a few healthy lifestyle choices.
1. Replenish Your Gut with Probiotics
Probiotics contain microorganisms that can help optimize the natural balance of your gut's microbiome, which, in turn, can help promote a healthy gut.
“The subtle balance of good and bad bacteria throughout the microbiome is continuously in flux,” explains Trattner. “As we introduce invaders such as infections, antibiotics and environmental chemicals or distress it through poor diet and other external factors, we disturb the efficacy of this ecosystem, destroying good bacteria and causing disease.”
That said, turning to probiotic supplements may not be the best course of action to resolve this pervasive problem. Research published this fall showed that over-the-counter supplements are, by and large, unhelpful – and could actually be harmful – in repopulating one’s gut following a course of antibiotics.
Instead, Ahmad suggests ingesting natural sources of probiotics, like kefir, yogurt, kimchi, or sauerkraut.
2. Feed Your Gut What It Wants
According to our experts, certain foods are true warriors in promoting a healthy gut and thus a healthy brain.
- leafy green vegetables
- high-fiber whole grains, which contain prebiotics that studies have shown can reduce stress hormones in humans
- omega-3 fatty acids, which studies have shown can improve both brain and gut health and even reduce symptoms of depression
- foods rich in polyphenols such as chocolate, green tea, and coffee.
There are also some foods you may want to avoid, including any foods that lead to general inflammation. These include high-fat foods, like fatty meats and fried foods, as well as overly processed foods.
“I specifically say nothing that is white," explains Ahmad. "Stay away from a lot of enriched flour, all white bread, white pasta."
For more examples of great foods that feed both your gut and your brain, Max Lugavere’s New York Times bestseller Genius Foods is a fantastic resource.
3. Treat Yourself with Kindness
Lifestyle choices that affect the gut-brain axis include sleep habits and stress levels. Practices like forest bathing, establishing a regular sleep schedule, or even taking time to play with your kids have been proven to help reduce stress and thus improve both psychological and physiological symptoms.
But this is just the beginning! Any small step you can take towards promoting better mental health hygiene – from spending time with friends to taking time away from screens to simply enjoying a meal with your family – can start the cycle of improved health for your gut and your brain.
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