If you’ve ever experienced butterflies in your stomach before a speech, you knew the sensation didn’t result from a lost monarch. But this common experience—your gut seeming to act out your brain’s anxiety—is an everyday example of fascinating new research into the interconnected worlds inside us.
While your stomach doesn’t contain butterflies, there are tiny organisms in there that are engaged in a conversation with your brain about that stress you’re experiencing. These organisms and their home could be far more powerful than we’ve realized, according to a burst of new studies. Many of the tens of trillions of organisms in your gut, or gastrointestinal tract, can help maintain good digestion and health . But some of them are not so cooperative: When they take over, they wreak havoc. That might mean you get food poisoning or make more bathroom trips than you’d like—but some might have bigger implications. These nasty bugs could be sending the brain signals connected to brain-related disorders including anxiety and Alzheimer’s disease .
So, is your gut the key to a healthy brain? Here’s what you need to know about the gut-brain connection. What is the gut microbiome?
With the help of everyday people, University of California San Diego researchers have uncovered new facets of the worlds within us. As part of the American Gut Project , more than 10,000 people from around the world mailed in their poop (yep). Scientists analyzed it to understand how organisms inside us—our microbiomes—interact with diet, lifestyle, and disease.
Learn more about the powerful gut-brain connection in a free webinar on June 9 , moderated by Joan Lunden and hosted by Prevention , HealthyWomen , and the Women’s Alzheimer’s Movement at Cleveland Clinic .
You may remember the word “biome” from biology class—a habitat such as desert or grassland, designated based on local climate and plant life. Our bodies contain their own worlds, unique habitats of trillions of wee beasties—viruses, fungi, bacteria, and other microorganisms living on us and inside us. In humans, microbes gather in these worlds on the skin, in the nose , and in the gastrointestinal tract (a.k.a. the gut). Over the past 20 years, experts have refined techniques to “fingerprint” the gut’s cast of microbes through sequencing DNA, says Ami Bhatt, M.D., Ph.D. , an associate professor of medicine and genetics at Stanford University.
You’ve had a microbiome since the day you were born, and it’s been evolving and growing with you. On your ride through the birth canal, your gut filled with a wide cast of microorganisms passed along by your mom. Then skin-to-skin contact, first foods, infections (and antibiotics), and all those germy toys changed your microbiome. Each new interaction, from childhood on, brings in guest stars, removes old standbys, and casts long-term recurring roles— your gut’s world is constantly in flux.
Animal and human research has found that the gut microbiome can be influenced by environmental factors such as chronic stress, artificial sweeteners, pesticides, disinfection, and ultrafine particles in polluted air. You can pick up new gut bacteria from your pet or a bad meal, Dr. Bhatt notes. Ultimately, microbial worlds wholly unique to you inhabit your body.
Helpful gut microorganisms have processes for breaking down foods and turning them into ingredients our bodies use. They develop the immune system, block pathogens, synthesize vitamins , and more. How the gut talks to the brain
In the past, you’ve probably lost your appetite because of stress or sadness—or falling in love. Maybe you’ve “followed your gut” or made a “gut decision.” These familiar terms and experiences clue us in to why some researchers are now calling the gut our “second brain” and saying bacteria may be the “master puppeteers” of our brains.
Scientists aren’t sure yet how the gut’s microbiome influences the brain—but it seems to be a fascinating two-way relationship. For example, among middle-aged adults, a more diverse microbiome was associated with better performance on cognitive tests . Various theories posit that the gut produces molecules that signal the brain via the bloodstream or the enteric nervous system . For example, specific gut bacteria can detect and increase the production of serotonin, which is associated with feelings of contentment. In fact, 90% of the body’s serotonin is made right in the gut . Another kind of bacteria commonly found in the human gut, Lactobacillus rhamnosus , actually contains a neurotransmitter that can help calm anxiety . Other bacteria may influence our social behavior and interactions and our responses to stress.
“It’s a two-way street of feedback loops” between the gut and the brain, says researcher Laura Cox, Ph.D. , a Harvard assistant professor seeking to understand how the microbiome can affect the brain in aging. What happens in the brain when gut bugs go bad
Sometimes unhelpful critters stage a takeover of the gut. This overpopulation can lead to gut dysbiosis , a negative imbalance that seems to cause static in the body’s communication lines and influence the brain’s everyday work. For example, gut dysbiosis is associated with depressive-like behaviors. In an animal study, transferring a mood-disordered animal’s gut bacteria into a healthy animal led to depressive symptoms for the formerly well animal, says Smita Patel, D.O., a neurologist and sleep specialist at iNeuro Institute . Other research is investigating the links between the gut microbiome and ADHD , autism spectrum disorders , anxiety , and stress . Unhelpful gut microbes may create irritants to the immune system that travel through the bloodstream and influence the brain’s immune cells. For example, the guts of Alzheimer’s disease patients show a lack of diversity compared with those of similar adults and are often overpopulated with a specific microbe. This microbe may impair immune functions related to clearing a plaque built upon the brain’s structures that is related to Alzheimer’s symptoms . Sex-based differences come into play as well, says Cox. The gut microbiota can regulate levels of hormones, including estrogen. When gut dysbiosis sets in, estrogen levels can change, possibly influencing cognitive decline.
Fascinating research is now being done by the Alzheimer Gut […]