Have you ever had a gut feeling or butterflies in your stomach? Recent studies show that your brain affects your gut health and your gut affects your brain health. The communication system between your gut and brain is called the gut-brain axis.
How are the Gut and Brain Connected?
These two organs are connected both physically and biochemically in a number of different ways. Your brain and central nervous system is made up of neurons that tell your body how to behave. There are approximately 100 billion neurons in the human brain (3). Interestingly, your gut contains 500 million neurons, which are connected to your brain through nerves in your nervous system (4).
The vagus nerve is one of the biggest nerves connecting your gut and brain. It sends signals in both directions (5).
Breit, S., Kupferberg, A., Rogler, G., Hasler, G. (2018). Vagus nerve as modulator of the brain-gut axis in psychiatric and inflammatory disorders. Frontiers in Psychiatry. 9:44. doi: 10.3389/fpsyt.2018.00044
Neurotransmitters
Your gut and brain are also connected through chemicals called neurotransmitters which are produced in the brain control feelings and emotions. For example, the neurotransmitter serotonin contributes to feelings of happiness and also helps control your body clock (6). A large proportion of serotonin is produced in the gut (7). Your gut microbes also produce a neurotransmitter called gamma-aminobutyric acid (GABA), which helps control feelings of fear and anxiety (8).
Gut Microbes Affect Inflammation
Your gut-brain axis is also connected through the immune system. Gut and gut microbes play an important role in your immune system and inflammation by controlling what is passed into the body and what is eliminated (9). If your immune system is switched on for too long, it can lead to inflammation, which is associated with a number of brain disorders like depression and Alzheimer’s disease (10). Lipopolysaccharide (LPS) is an inflammatory toxin made by certain bacteria. It can cause inflammation if too much of it passes from the gut into the blood. This can happen when the gut barrier becomes leaky, which allows bacteria and LPS to cross over into the blood. Inflammation and high LPS in the blood have been associated with a number of brain disorders including severe depression, dementia and schizophrenia (11).
There are foods that are beneficial for the gut-brain axis. Here are some of the most important ones:
Omega-3 fats: These fats are found in oily fish and also in high quantities in the human brain. Studies in humans and animals show that omega-3s can increase good bacteria in the gut and reduce risk of brain disorders (12).
Fermented foods: Yogurt, kefir, sauerkraut and cheese all contain healthy microbes such as lactic acid bacteria. Fermented foods have been shown to alter brain activity (13).
High-fiber foods: Whole grains, nuts, seeds, fruits and vegetables all contain prebiotic fibers that are good for your gut bacteria. Prebiotics can reduce stress hormone in humans (14).
Polyphenol-rich foods: Cocoa, green tea, olive oil and coffee all contain polyphenols, which are plant chemicals that are digested by your gut bacteria. Polyphenols increase healthy gut bacteria and may improve cognition (15).
Tryptophan-rich foods: Tryptophan is an amino acid that is converted into the neurotransmitter serotonin. Foods that are high in tryptophan include turkey, eggs and cheese.
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