The Gut–Brain Axis: Why the Gut Is Often Called the “Second Brain”
When we think about brain health, we usually focus on learning, memory, and emotions. But in recent years, scientists have discovered something fascinating: the gut and the brain are deeply connected. This communication system is known as the gut–brain axis, and it plays an important role in mood, digestion, and overall well-being. What Is the Gut–Brain Axis? The gut–brain axis is a two-way communication network between the digestive system and the brain. They constantly send signals to each other through: The nervous system (including the vagus nerve) Hormones Immune system pathways Gut microbes (microbiome) This means what happens in the gut can influence the brain; and what happens in the brain can also affect the gut. For example, stress may lead to stomach discomfort, while an unhealthy gut may affect mood or focus. Why Is the Gut Called the “Second Brain”? The gut is sometimes called the “second brain” because it contains its own complex nervous system called the enteric nervous system (ENS). The ENS has: Over 100 million nerve cells The ability to function independently from the brain Direct communication with the central nervous system This system helps control digestion, but it also plays a role in emotional responses and overall gut comfort. Because of this complexity, scientists often describe the gut as a “mini brain” inside the body. Serotonin: The Key Link Between Gut and Mood One of the most important connections between the gut and brain is serotonin. Serotonin is a neurotransmitter often associated with: Mood balance Sleep regulation Emotional well-being Appetite control What many people don’t realize is that about 90% of the body’s serotonin is produced in the gut, not the brain. Gut microbes help regulate the cells that produce serotonin in the digestive system. While gut-produced serotonin does not directly act on the brain, it plays a key role in: Gut movement and digestion Gut–brain signalling pathways Overall balance of the nervous system This explains why gut health is often linked with emotional well-being. How the Gut Affects the Brain? When the gut microbiome is balanced, communication between the gut and brain tends to function smoothly. A healthy gut environment may support: More stable mood patterns Better stress response Improved digestion comfort Enhanced overall well-being On the other hand, an imbalanced gut microbiome may send signals that influence discomfort, sensitivity, or changes in appetite and mood. How to Support a Healthy Gut–Brain Connection? Parents and individuals can support this connection through simple daily habits: Eating a balanced diet rich in fibre (fruits, vegetables, whole grains) Including fermented foods such as yogurt or kefir Managing stress through rest, play, and routine Staying physically active Ensuring good sleep patterns These habits help maintain a diverse gut microbiome, which is important for gut–brain communication. The gut is more than just a digestive organ. It is an active communication hub closely connected to the brain. With its own nervous system and its role in producing key neurotransmitters like serotonin, it is easy to understand why scientists often refer to it as the “second brain.” Taking care of gut health through diet and lifestyle may support not only digestion but also emotional balance and overall well-being. References Mayer, E.A. (2011). Gut feelings: the emerging biology of gut–brain communication. Nature Reviews Neuroscience. Carabotti, M. et al. (2015). The gut–brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of Gastroenterology. Yano, J.M. et al. (2015). Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis. Cell. Cryan, J.F. & Dinan, T.G. (2012). Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour. Nature Reviews Neuroscience.









