Have you ever felt anxious and then had a stomach ache? Have you also wondered how an emotional feeling such as anxiety would elicit a physical symptom such as stomach upset? This happens because your gut and brain are linked through a connection referred to as the gut-brain axis. In the past decade, more and more scientific evidence is emerging about the interconnectivity of the gut and brain, and how this connection modulates and regulates the development of chronic diseases and mental illnesses.

Mechanistically, the gut and brain are connected through the vagus nerve, which is a component of the autonomic nervous system. This nerve connects the enteric nervous system in the gut to the central nervous system which the brain is a part of.

Apart from the vagus nerve directly connecting the gut and brain, there are a multitude of metabolites, neurotransmitters, hormones, immunological factors, and more produced in the gut. These molecules are released through autonomic neurons and circulate to the brain for communication. For example, enteroendocrine cells, which are found in the gut, are responsible for regulating various physiological processes via hormones. After having a delicious meal, these enteroendocrine cells release peptides that communicate to the nervous system to stop eating and signal satiety to the brain.

This process of communication from the gut to the brain can be influenced by the gut microbiome. The gut microbiome, by definition, is the totality of microorganisms known as microbiota (bacteria, viruses, fungi, etc), and their genetic material present in the gut. Interestingly, the food we eat plays a role in shaping our gut microbiome. In fact, this starts from the first months as a newborn. Studies have shown that breastfeeding, for example, allows for the growth of Bifidobacterium species which are an important part of the infant microbiome. Together with Lactobacillus species, these bacteria produce gamma aminobutyric acid (GABA) which is an inhibitor of several neural pathways. Importantly, GABA blocks some nerve signals in the brain to reduce fear, anxiety, and stress. Consequently, a deficiency of GABA in the body could worsen mental health conditions, such as anxiety.

For adults, food also plays a significant role in engineering the microbiome and impacting mental and overall health. The ketogenic diet, characterized by high fat, moderate to low protein, and very low carbohydrates, is known for its anti-seizure effects, such as counteracting epilepsy and has been shown to mediate these effects by modulating the gut microbiome. Western diet, on the other hand, characterized by high saturated fat and high carbohydrates, not only alters the gut microbiome but leads to increased inflammation, which has been proven to contribute to anxiety and depression. There are other numerous studies correlating the gut microbiome and other mental health conditions, such as autism, Alzheimer’s, etc.

Now, it makes sense why the gut is sometimes referred to as the “second brain” as the gut connects and communicates with the brain. Because of the gut-brain axis, it is important to keep our gut and brain in good health, giving a whole new meaning to the phrase, “listen to your gut!”

The connection between the gut and brain is often referred to as the brain-gut microbiome axis. This term highlights the integral role of the gut microbiome in maintaining communication between the gut and brain. The gut-brain axis microbiome is influenced by multiple factors, including diet, stress, lifestyle, and even sleep patterns.

Stress has a significant impact on the mind-gut connection. Chronic stress triggers the release of cortisol, a hormone that disrupts gut lining integrity, leading to a condition known as "leaky gut." This condition allows harmful substances to pass into the bloodstream, potentially causing inflammation that negatively impacts brain function. Addressing stress through mindfulness practices, yoga, and regular exercise can help restore balance in the gut-brain connection.

Maintaining the gut-brain connection requires intentional lifestyle choices. Here are some tips:

1. Eat Gut-Friendly Foods: Incorporate fiber-rich foods, fermented products, and whole foods into your diet. Avoid processed and sugary items that can harm the microbiome.
2. Include Probiotics and Prebiotics: Probiotics, such as those found in yogurt and supplements, introduce beneficial bacteria to the gut. Prebiotics, such as inulin-rich foods, feed these bacteria.
3. Get Enough Sleep: Poor sleep disrupts both the brain and gut, emphasizing the importance of good sleep hygiene.
4. Exercise Regularly: Physical activity promotes a diverse microbiome and reduces stress, enhancing the mind-gut connection.

The interconnection between the brain and gut through the gut-brain axis microbiome is a testament to the intricate relationship between physical and mental health. From early development to adulthood, maintaining a healthy gut microbiome can reduce inflammation, regulate neurotransmitters, and support overall well-being. Understanding this connection empowers us to make informed lifestyle choices, reminding us once again to “listen to your gut!”