Which organ sends neural signals to other parts of your body, produces various neurotransmitters, and affects your mood and feelings? If you answered “the brain”, you’re absolutely correct! But did you know that you have another biological system that does all those things, and much more?
The gastrointestinal system, or the gut, is well-known for its digestive functions. Less commonly known is the role the gut plays in managing your overall emotional well-being. In fact, the gut and the brain are deeply interconnected, making the gut just as important as the brain in influencing your mood and how you feel!
The Gut-Brain Axis
It turns out that common phrases such as having “butterflies in your stomach”, or a “gut-wrenching” experience, are no coincidence. These feelings are a result of the intertwined nature of the brain and the gut, a connection referred to as the gut-brain axis. The gut-brain axis is a “bidirectional communication network” linking the brain and the gut. This means that the brain can influence intestinal activities, and the gut can influence mental health, mood, and cognition.
In fact, a recent study discovered that the gut and brain share a direct connection via a dedicated neuron circuit, bypassing the bloodstream entirely. This neuron circuit allows the gut and brain to send messages to each other within seconds, much faster than it would take for hormones to travel back and forth using the bloodstream. What’s more, the gut itself is “lined with more than 100 million nerve cells”, forming the largest collection of neurons found outside of the human brain. No wonder the gut is often nicknamed the “second brain”!
Keeping Your Gut Microbiome Healthy
You may have noticed the connection between anxiety and digestive issues in your own life. Have you ever had to give a speech in front of a large crowd, and felt your stomach “drop”? Maybe your heart started racing, your palms became sweaty, and then suddenly you found yourself needing the bathroom. Because of the gut-brain connection, it’s no surprise that anxiety or depression may lead to digestive problems. But what is surprising is that it works both ways!
Growing evidence has shown that the health of the gut microbiome “is an important factor determining both the risk of development of depression and persistence of depressive symptoms”.
So how do you keep your gut microbiome healthy? Read on to find out!
The Gut Microbiome: A Whole New World
This “second brain” is actually an entire ecosystem, made up of human neurons, but also various bacteria and other microorganisms. Mounting evidence suggests that gut microbiota play a critical role in influencing the interactions between the gut and the brain.
For example, serotonin, a hormone termed the “happy chemical” because it contributes to well-being and feelings of happiness, is most often conceived of as a neurotransmitter produced in the brain. However, over 90% of serotonin in the body is estimated to be produced in the gut, with the help of various gut microbiota. Specifically, particular species of gut microorganisms stimulate endocrine cells to produce serotonin. Because serotonin levels are directly related to emotional well-being, the health of your gut microbiome is an important factor in determining your overall mood.
The gut microbiome is incredibly diverse, with literally trillions of microorganisms constantly interacting in complex symbiotic relationships. A healthy gut is like a healthy forest—with a high diversity and balance between species, species interactions, and ecological resources. An unhealthy gut, on the other hand, is like a troubled, damaged ecosystem—with a low diversity and imbalance in species, their populations and interactions, and resources. Just like in a forest, if any of the complex relationships between the gut microbiota are disrupted, unpredictable, often negative, consequences may follow.
An example of this is IBS (irritable bowel syndrome), which can be understood as a disruption of the complex relationships between gut microorganisms. Also, malnutrition, obesity, and even neurological disorders (including anxiety and depression) are associated with an imbalance between gut microbiota and their human host.
Cover photo credit: https://unsplash.com/@averey