Once upon a time, humans were little more than monkeys. We had a smaller skull than we do now, and it primarily consisted of the limbic brain. That’s the deep, emotional, intuitive part of the brain—surrounded by a slim sliver of the outer cortex.
Over time, our digestive tract shrank as our outer cortex grew, becoming as dense as the limbic brain. The growth of this rational part of the brain brought about articulated speech and the ability to predict and plan for the future. As we became more logical and able to communicate and exist in larger tribes, we talked more and felt less. We moved away from emotions and intuition to logic and facts, and survival through competition became our means to an end.
Now, we live in a world that values logic and considers emotions as weak. It seems like decisions based on intuition have little or no place in today’s society. Over time, we’ve neglected the gut and the limbic brain, and placed the cortex on a pedestal. We’ve demoted depth, passion and instinct to fixate on surface-level capabilities—exams, rote-learning, and transactional relationships. We are more connected with material gain than joy. At the same time, increased stress, processed food, and antibiotics have massively diminished the biodiversity of our gut flora, which compromises more than our physical resilience.
The science of trusting your gut
One thing is now a scientific certainty: the gut-brain link is far from a mystical “sixth sense.” As a neuroscientist, I share the research to back this up with my skeptical clients. I start by explaining that their gut produces a staggering 90% of their serotonin. This neurotransmitter acts as a “happy” hormone that regulates mood, and in the gut as a paracrine-signaling molecule. As a result, it induces a change in close-by cells in the body.
The gut houses the enteric nervous system. It works unconsciously in much the same way you breathe and the way your heart beats—without any intervention from your conscious brain. The gut is a connected system that links back to the brain in several ways, including the vagus nerve and cytokine transmission. This is a three-way communication between the brain, gut neurons, and the gut bacteria.
Neurobiological research has revealed a complex communication system between the millions of neurons embedded in the gut walls and the limbic brain, and found that this system is integral to our decision-making capability. The gut–brain system helps govern not only the healthy functioning of our digestive system but also complex brain functions like motivation and wisdom.
Your well-being and the brain
The physical health of our gut supports the healthy functioning of this three-way system. A 2016 research paper published in Trends in Neurosciences shows that taking a good-quality probiotic for one month to rebalance gut flora reduces negative thinking, while according to a 2015 study in the Netherlands, probiotic supplementation seemed to reduce “cognitive reactivity” to low mood. Just as our thinking is slower and harder when we have a cold or are in pain, a depleted, inflamed, or struggling gut will cloud our intuition.
Growing research links the gut microbiome to our immune system, as the quality of immune cells that are produced in the bone marrow relate to the quality of bacteria in the gut. This is an exciting area of research that will likely enhance our understanding of the relationship between our immunity, resilience, and brain performance.
The role of stress
Research shows that the brain continually communicates stress levels to the gut. When it’s stressed, the brain lets the gut know via sympathetic nerve fibers. The gut responds to this by using less energy for digestion. When stress is constant, it puts a negative drain on the gut’s resources and results in a range of symptoms—whether that’s a change in appetite, bloating, or diarrhea. Over time, the gut walls can weaken, and immune cells secrete large amounts of signal substances that lower the stress threshold in our body and brain. An unwell gut may mean we feel the effects of stress long after the cause of that stress has disappeared.
How to improve your gut-brain function
Supplementing with a good quality probiotic, eating a healthy diet packed with vegetables, and low in red meat and refined foods, particularly sugar, is an excellent way to support a healthy gut. But to better tune into your gut wisdom, you’ll need to train yourself to listen out for the feedback your gut is giving you. Here are simple ways that you can do that:
- Keep an intuition journal. Make it a habit to journal about your emotions and your decision-making process. Reading back over about six months of journal entries can be enlightening, not only in terms of how things change when you travel, eat poorly, or get stressed—but also in terms of how your decisions pan out when you trust your gut rather than always default to logic.
- Reconnect to your body. Tuning into your intuition will help you recognize when you need to rest and recuperate after a busy project at work or a lot of socializing. Spend a moment a few times a day focusing on sensations and intuitive feelings in your body. You might even symptoms of a serious illness that you’d otherwise attribute to stress or psychology.
When not to trust your gut
Of course, there are times when you shouldn’t trust your gut. For starters, we all have prejudices, and many of these are embedded at a gut level. Some are epidemic in society, like the beliefs “people like us” are likely to make the best colleagues, friends, and partners. Some, like appetite for risks and emotional triggers, are individual. So next time you feel tempted to react mindlessly, stop to consider whether unconscious bias has taken over.
Also, take your “gut instinct” with a pinch of salt if it’s telling you you’re not good enough to apply for a particular job. A commonly cited statistic from a Hewlett Packard internal report demonstrates that most women feel they needed to meet 100% of the job criteria to apply for a position. Men, on average, believed they should apply if they met 60% of the criteria. So if you get your gut muddled with your critical inner voice, you might just be missing an opportunity.
Tara Swart is a neuroscientist, executive adviser, author, and medical doctor. She is the author of The Source: The Secrets of the Universe, The Science of the Brain.