You are walking on stage. Hundreds of eyes are watching you. Your palms are sweating, and the butterflies are turning and tossing in your stomach. The nervous flutter that you are experiencing is (you guessed it) a “gut feeling”—an intuitive reaction to a situation.
What you may not know is that the gut feeling can be explained at a microbiological level. When you experience any emotion, your brain communicates with the millions of nerve cells in your digestive tract, resulting in funny sensations throughout your body—examples of gut feelings. It may be easy to chalk it up to emotions because we experience gut feelings all the time. But what if the gut plays a bigger role than simply controlling our feelings?
The gut is home to trillions of bacteria and microbes inhabiting the intestines, forming the gut microbiome. Along with breaking down food, these microbes are connected to mood and cognition, thus gaining the “second brain” nickname.
But how does this work?
The gut and brain are in constant contact through the gut-brain axis, a complex network linking the nervous system with gut microbes. Neurotransmitters, the brain’s signaling molecules influencing your mood, are primarily produced by gut bacteria. Interestingly, around 95% of your body’s serotonin, the “happy chemical,” is produced and stored in the gut. So, when your microbiome is imbalanced, your emotions may be imbalanced too.
- 95% of your body’s serotonin, the “happy chemical,” is produced and stored in the gut.
- The gut and brain are in constant contact through a complex network linking the nervous system with gut microbes.
- Each person has a unique set of microbes in their gut, influenced by their birth, genetics, and environment.
- Diet impacts the gut, which can impact mental well-being.
Dr. Reece Knippel is a trained microbiologist and head of the Clinical Bacteriology Laboratory in Vaccines and Immune Therapies at AstraZeneca. His work illuminates the role of the gut microbiome in developing new therapeutics. The gut microbiome is not just critical in digestion; changes in the gut bacteria can also lead to “neurological issues—anxiety, depression, and even weight gain,” Knippel says.
What throws the microbiome out of balance? Factors such as diet, stress, and antibiotics affect the gut. The Western diet, consisting of high amounts of processed foods and sugar, can lead to an overgrowth of harmful bacteria, linked to inflammation and inflammatory bowel disease.
Many, however, are unaware of their diet’s effect on their mental well-being. Unfortunately, there is no “magic pill” or single diet that can fix all health issues. Although “diet is a huge aspect of the microbiome, so is genetics,” Knippel says. From birth, an individual’s gut already begins to develop, affected by how the person was born (natural birth, C-section, etc.), whether breastfed, or exposed to antibiotics. Each person has a unique set of microbes in their gut, influenced by their birth, genetics, and environment; therefore, certain diets may benefit one person but harm or have no effect on another.
Certain foods, however, are generally beneficial for everyone, Knippel explains. The Mediterranean diet, known for fresh fruits and vegetables and fish, is “high in healthy fats that could lead to the fostering of good bacteria.”
While there may be generally “good” and “bad” diets, there is no all-in-one fix. The science is still evolving, and experts caution against using supplements as a cure-all. The combination of “living a good lifestyle, eating a balanced diet, and avoiding harmful activities such as smoking and drinking” is critical to maintaining a healthy microbiome,” says Knippel. Chronic stress, for example, may alter gut composition and increase inflammation, while consistent physical activity is commonly linked to a diverse microbiome.
By studying the various factors influencing the microbiome, Knippel envisions a future where personalized dietary treatments can optimize an individual’s health based on their unique gut microbiome. “It is hard to nail down a single blueprint because everyone is so different,” he says. “But we can start by observing each person’s microbiome…and finding ways to correct specific issues through different types of interventions.”
But the road remains rocky. The microbiome is incredibly complicated. No two people share the same gut bacteria, making it difficult to establish standardized treatments. Ethical concerns also arise around the accessibility of these potential treatments.
So, next time you feel those butterflies in your stomach or a sudden sense of clarity, remember that your gut and brain are constantly messaging each other. Knippel says, “We are not only a super complex molecular machine, but also a little world inside of us.”
Sources
“The Brain-Gut Connection.” Johns Hopkins Medicine, June 20, 2024. www.hopkinsmedicine.org/health/wellness-and-prevention/the-brain-gut-connection
“Can Probiotics Improve Your Mood?” Johns Hopkins Medicine, June 20, 2024. www.hopkinsmedicine.org/health/wellness-and-prevention/can-probiotics-improve-your-mood
Knippel, Reece. Interview conducted by Ellen Bu. August 2, 2024.
Loconti, Christine. “The Gut Brain Axis: Learn More about Your Second Brain.” Musically reviewed by Minesh Khatri, WebMD, WebMD, Feb. 18, 2024, www.webmd.com/digestive-disorders/what-to-know-about-gut-brain-link
Ochoa-Repáraz, Javier, and Kasper, Lloyd H. “The Second Brain: Is the Gut Microbiota a Link between Obesity and Central Nervous System Disorders?” Current Obesity Reports, 5(1):51-64, March 2016.
www.ncbi.nlm.nih.gov/pmc/articles/PMC4798912/#:~:text=The%20gut%2Dbrain%20axis%20is,changes%20that%20lead%20to%20obesity.
Woo, Clement. “Our Second Brain: More than a Gut Feeling.” UBC Neuroscience, Oct. 15, 2021. neuroscience.ubc.ca/our-second-brain-more-than-a-gut-feeling/#:~:text=Many%20of%20these%20microbes%20live,not%20the%20other%20way%20around
Editorial Team
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Mentor
- Paige Jarreau is a science communicator passionate about collaborating with diverse creatives and stakeholders to make science more engaging and inclusive.
Reece Knippel, Ph.D.
Reece Knippel, Ph.D., is the head of the Clinical Bacteriology Laboratory in Vaccines and Immune Therapies at AstraZeneca. He has over 15 years of experience in vaccine development, monoclonal antibody therapies, bacteriology, host-pathogen interactions, and molecular biology. He is a classically trained microbiologist, obtaining his Ph.D. at Vanderbilt and postdoctoral training at John Hopkins, where he worked on the interplay of the microbiome in cancer development.
