You know that feeling when your stomach tightens before a job interview? Or when a bad piece of news makes you queasy? That is not in your imagination. Your gut is not just digesting your lunch. It is, in a sense, thinking.
Researchers now call the gut the body's second brain, and the science behind this idea is moving fast. Tucked into the lining of your digestive tract sits a network of around 100 million neurons, a system so sophisticated it can operate without instructions from the brain in your head. It also seems to be in constant conversation with your central nervous system, your immune system, and the trillions of microbes living in your gut.
The gut-brain axis is no longer a fringe concept. It is one of the most active areas of medical research today. Here is what scientists are starting to understand.
The Hidden Brain in Your Belly
Hidden inside the walls of your digestive tract is something called the enteric nervous system, or ENS. According to research by Professor John Furness, published in Nature Reviews Gastroenterology & Hepatology in 2012, the ENS contains around 100 million neurons, more than the spinal cord. It runs the length of your gut, from oesophagus to rectum, and is sometimes described as a brain in its own right because it appears to function independently of the central nervous system.
The ENS is what keeps your digestion running when you are not paying attention. It seems to manage everything from muscle contractions that move food along, to the release of digestive enzymes, to local immune responses. Most of this happens without conscious thought, which may be why we so often ignore it until something goes wrong.
The interesting bit, though, is what happens when the ENS talks to your brain.
The Information Highway: Your Vagus Nerve
The main line of communication between your gut and your brain appears to be the vagus nerve, the longest cranial nerve in the body. It carries information in both directions, but researchers believe around 80 to 90 percent of vagus nerve fibres send signals from the gut up to the brain, not the other way around. In other words, your gut is doing a lot more talking than listening.
Research by Breit and colleagues, published in Frontiers in Psychiatry in 2018, suggests the vagus nerve may play a role in regulating mood, stress responses and inflammation. Some studies indicate that people with depression, anxiety and irritable bowel syndrome show altered vagal activity, although the picture is still being pieced together.
This is why some scientists now describe the gut-brain axis as a two-way street with very heavy traffic in one direction.
The Microbial Influence
Here is where it gets really interesting. The neurons in your gut do not work alone. They appear to be deeply influenced by your gut microbiome, the trillions of bacteria, viruses and fungi that live inside your digestive tract.
A landmark 2019 review by Professor John Cryan and colleagues, published in Physiological Reviews, summarised the emerging evidence that gut microbes may produce neurotransmitters including serotonin, dopamine and GABA, all of which are involved in mood and brain function. The researchers concluded that the microbiota-gut-brain axis may have implications for conditions ranging from anxiety and depression to Parkinson's disease, although they cautioned that much of the research is still at an early stage.
The takeaway is not that your gut bacteria are running your life. It is that the conversation between your gut, your brain and your microbes seems to matter more than scientists previously thought.
What This Might Mean for You
Most of us were taught to think of the gut as plumbing. Useful, occasionally noisy, mostly to be ignored. The emerging science is starting to flip that idea on its head.
It does not mean you should panic about every gut twinge, or assume your digestion is the answer to every mood. What it does suggest is that paying attention to your gut, what it is telling you, when it acts up, what calms it down, might be a useful habit. The body has been trying to tell us something all along.
As the science of the gut-brain axis continues to develop, the case for tuning in feels more compelling than ever. Join our 7-day gut cleanse to give your gut the refresh it needs.
References
- Furness, J. B. (2012). The enteric nervous system and neurogastroenterology. Nature Reviews Gastroenterology & Hepatology, 9(5), 286-294.
- Breit, S., Kupferberg, A., Rostock, G., & Hasler, G. (2018). Vagus nerve as modulator of the brain-gut axis. Frontiers in Psychiatry, 9, 44.
- Cryan, J. F., et al. (2019). The microbiota-gut-brain axis. Physiological Reviews, 99(4), 1877-2013.
This content is for informational purposes only and does not constitute medical advice. If you have concerns about your digestive health, please speak to a healthcare professional.
