It might sound like science fiction, but it's true: Your brain and your gut share your fears and desires, your happiest moments and deepest sorrows. Just as memories, good or bad, live on in your mind, they also take root in your gut. And the health of that dark inner world is vulnerable to emotional and physical stress from the time you are conceived until the day you turn 20. An unhappy childhood can wreak havoc on your digestive system for the rest of your life.
“News is breaking every day linking the gut-brain connection to a variety of ailments,” says Dr. Jay Pasricha, professor of medicine and director of the Johns Hopkins Center for Neurogastroenterology, and a leader in research on the mind-gut connection. “It used to be that we thought of this connection as a one-way street—from the brain to the gut. If you experienced anxiety, for instance, you may feel queasy in your stomach. We are now beginning to see signals from the gut that can by themselves determine mood, and even possibly lead to anxiety and depression in some instances.”
Instinctively, you know that your brain and belly are linked. You’ve made gut decisions, had gut-wrenching experiences or felt butterflies in your stomach. Sometimes, you know something to be true because you feel it in your gut.
“The mind–body connection is far from a myth; it is a biological fact, and an essential link to understand when it comes to our whole body health,” writes Dr. Emeran Mayer, author of The Mind-Gut Connection: How the Hidden Conversation Within Our Bodies Impacts Our Mood, Our Choices, and Our Overall Health.
Unseen by you, your gut contains a microbiome—a vast community of genes, cells and micro-organisms that work 24/7—with capabilities that surpass all your other organs and even rival your brain. “It has its own nervous system, the enteric nervous system, or ENS, and is often referred to in the media as the ‘second brain,’” writes Mayer.
“News is breaking every day linking the gut-brain connection to a variety of ailments.”
The gut connects to the brain through nerve cables that can transfer information in both directions, and through communication channels that use the bloodstream. Gut signals to the brain not only generate gut sensations—fullness after a meal, nausea, discomfort, well-being— but also trigger responses that the brain sends back to the gut, generating distinct gut reactions. “The brain doesn’t forget about these feelings, either,” says Mayer. “Gut feelings are stored in vast databases in the brain, which can later be accessed when making decisions. What we sense in our gut will ultimately affect not only the decisions we make about what to eat and drink, but also the people we choose to spend time with and the way we assess critical information as workers, jury members and leaders.” Incredibly, our gut can help us predict the future.
“It is becoming clear,” Mayer says, “that one of the most important functions of our brain is to make predictions about the future, based on a vast database of past experiences. It makes these predictions on a wide range of timescales from milliseconds to days—exactly the same process that is used by self-driving cars and by search engines which make predictions about our personal interests,” he explains. “A major source of the database which the brain uses to make these predictions are the signals from the gut that we accumulate over a lifetime, from the day we are born.” Influencing those gut sensations are the food we eat, the medications we take and the emotional states we experience. “Predictions that the brain makes range from personal decisions and choices [decisions based on gut feelings] to generating the most appropriate gut reactions to a particular meal.”
“The enteric nervous system doesn’t seem capable of thought as we know it, but it communicates back and forth with our big brain—with profound results,” says Pasricha. The ENS may trigger big emotional shifts experienced by people coping with irritable bowel syndrome (IBS) and other GI problems such as constipation, diarrhea, bloating, pain and stomach upset. Research suggests that irritation in the gastrointestinal system may send signals to the central nervous system that trigger mood changes, possibly explaining why a higher-than-normal percentage of people with IBS and other bowel problems develop depression and anxiety. “That’s important,” says Pasricha, “because up to 30 to 40 percent of the population has functional bowel problems at some point.”
“As incredible as this may sound,” adds Mayer, “your gut microbes are in a prime position to influence your emotions, by generating and modulating signals the gut sends back to the brain … In fact, we now know that your gut mirrors every emotion that arises in your brain.” Hence, the “gut wrenching” experience. “Your emotions, brain and gut are uniquely connected.”
As a gastroenterologist, Mayer sees patients who are suffering physically. Knowing about a patient’s first 18 years of life has become an essential part of the medical history he collects. He always asks patients whether they had a happy childhood? “Most of the time the patient had not made a connection between such experiences and their current medical problem,” says Mayer. “Their answers reveal a lot about the origin and nature of the stomach they experience as adults.”
There's a group of integrative psychiatrists who assess gastrointestinal bacterial markers looking for overgrowth of a particular strain of metabolites that affect mood and behavior. “The presence or overgrowth of this bacteria—Clostridia—inhibits dopamine conversion to norepinephrine,” says Dr. James M. Greenblatt, who teaches at Tufts University School of Medicine. “Patients with a significant overgrowth of this strain of bacteria will often have exacerbations of psychiatric problems including agitation, hyperactivity, and poor mood regulation. Once we address this problem, symptoms usually resolve,” he explains.
With gastroenterologists probing emotions and psychiatrists analyzing stomach issues, can you expect your doctors to ask more questions about your childhood (GI specialists) or your gut (psychiatrists)? “Although the commercial and medical interest in the gut-brain connection has increased dramatically over the last five years, the mental health community has lagged behind,” says Greenblatt. “There has been a considerable amount of research demonstrating the relationship between the brain and the gut, and animal studies have illustrated how certain strains of bacteria, or lack thereof, can affect mood and behavior. Despite the accumulating research demonstrating the therapeutic value of probiotics in mental health treatment, this is still a relatively new area of study.”
Greenblatt has seen remarkable transformations in his patients through the process of rebalancing the gut. “Typically, the conditions that resolve with high-dose probiotics are caused by an imbalance [dysbiosis] in the gastrointestinal tract where the ‘bad’ bacteria outnumbers the ‘good’ bacteria,” he explains. “Dysbiosis can be a reaction to stress. Changes in gut flora encourage the growth of pathogenic bacteria and limit the growth of beneficial bacteria, triggering an inflammatory response in the body. Several research studies have proven a direct correlation between inflammation and depression.” Greenblatt says the goal of probiotic treatment is to get the gut flora rebalanced. Once symptoms resolve, patients can maintain balance through dietary and lifestyle changes.
Keeping our brain-gut connection healthy and obstacle-free is no small feat in North America. The factory-farming methods employed to produce our food can contribute to gut distress, Mayer says, when animals live in filth, are confined to small areas and live their entire lives under stress. “Products that come from such chronically diseased animals are not good for our gut microbiota [your microbes] and not beneficial for our health.” That’s because the animals’ own brain-gut-microbiome axis has been severely modified by the conditions in which they’re raised.
But there are approaches that anyone can take today without spending a lot of money, Mayer says, pointing to a recent Science article proposing that we act as our own ecosystem engineers. “Consider your gut microbiome as a farm and your microbiota as your own personal farm animals, then decide what to feed them to optimize their diversity, stability and health,” says Mayer.
Your brain-gut microbiome is pretty much programmed after the first few years of life, tied to your genetic makeup and your exposure to medications, particularly antibiotics, early in life. Still, there are two things you can do to improve function in middle age, says Mayer. “One, realize that stress and every emotional state is reflected in the activity of the gut and its microbes, thereby influencing the digestion of food, and the feedback to the brain. Being mindful of this fact will guide you toward a greater awareness when to eat and how to eat,” he explains. “Two, realize that the composition of your diet has a major effect on this gut-brain communication: Diets high in animal fat and refined carbohydrates favor a low-grade inflammatory state in your gut and body, including the brain, with harmful effects on your health.” Preventing these negative top down (brain to gut) and bottom up (gut to brain) influences is likely to improve many aspects of your health, Mayer says.
It’s also important to take probiotics when taking antibiotics to treat an infection, says Greenblatt. Probiotics should be taken at the same time every day for at least 30 days after you finish your course of antibiotics. As we age, stomach acid production and digestive enzymes decrease, which can interfere with normal gut flora, leading to dysbiosis. If regular consumption of fermented foods is not a part of your diet, a probiotic supplement can provide many health benefits.”
For people in midlife looking to improve their mind-gut relationship, Pasricha suggests avoiding fad diets and instead follow an eating plan that is generally accepted as moderate and healthy. “You are a unique individual and your microbiome, like your genome, is likely to be relatively unique. So, pay attention to what you eat and what effects that may have on how you feel both in terms of body and mental symptoms. What you may respond to may be different than what the people in a clinical study may on the average. Become your own subject and scientific investigator to figure out what does or does not work for you. It’s part of the general process of taking responsibility for yourself.”