The Gut-Brain-Immune Connection

Last Updated on March 28, 2023 by Tracey McGrath

Ever felt butterflies in your tummy when you’re nervous or suffer from digestive problems during periods of stress and anxiety? This is a sign of the link between the gut and the brain. 

According to research, your brain and your gut are very interlinked and can have big effects on each other. The gut is actually being called “the second brain” by a lot of experts for this reason.¹ The gut and the brain are linked to the immune system too. Experts are investigating if autoimmune conditions may start in the gut.² 

What is autoimmune disease?

Let’s talk briefly about the immune system and autoimmune disease. 

Under normal circumstances, your immune system is designed to protect your body against viruses, bacteria and other nasties that can be harmful. It also produces antibodies that offer protection against viruses that you have been exposed to in the past.³ 

For some people, the immune system acts on healthy cells rather than invaders. The body produces auto-antibodies in response to this. This is known as autoimmunity. This anti-protective effect causes symptoms of autoimmune diseases.

The gut-brain link

Your brain has plenty of neurons, which tell your nervous system what to do. There is a less well known part of the central nervous system in the gut called the enteric nervous system, which lies in the lymphatic tissues below the lining of the intestines. It uses the same type of neurons and neurotransmitters as the central nervous system, hence the term of “second brain”.

The brain and gut are also linked by neurotransmitters, which are produced in the brain. One of the most well-known neurotransmitters is serotonin, which controls your mood. A lot of neurotransmitters are also present in your gut too. In fact, a huge proportion of serotonin is actually produced there, rather than in your brain. This means it’s super important to help your gut to produce the right levels of serotonin and be in the best shape to harness it. 

The gut-immune link

Your gut does a lot more than just digest and absorb nutrients from your food and excreting waste products. It’s also involved in helping your body to fight off bacteria and germs that could make you sick. There are a huge amount of immune cells in your gut. 

When “bad” bacteria gets the opportunity to outnumber the “good” bacteria in your gut, it sets the scene for a lot of health problems and this includes poor immunity and development of autoimmune diseases. Inflammation in the gut can be a big factor in autoimmune diseases, including autoimmune encephalomyelitis and multiple sclerosis.

Its role in Inflammatory Bowel Disease (IBD) probably won’t be a great surprise but an unhealthy gut can be involved in autoimmune diseases that are nothing to do with the gut itself.  

Studies on mice have shown that bacteria in the gut can travel to other parts of the body and trigger an autoimmune response, according to a study from Yale. The research focused on a bacterium called Enterococcus gallinarum, which has the ability to relocate itself to the lymph nodes, liver and spleen. They found that tissues outside of the gut kick started production of markers of autoimmune response. This was reduced in mice by using vaccines and antibiotics that targeted E. gallinarum, which stopped it growing in the tissues and meant it had less effect on the immune system. 

Researchers believe that dopamine signaling also controls the inflammatory response to prevent it going haywire. With autoimmune conditions, the immune system attacks healthy cells. Animal studies have suggested that controlling dopamine could help to stop this happening, although a lot more research needs to be done to confirm this possibility. 

Research is also finding links between Leaky Gut Syndrome and autoimmune conditions such as lupus, Hashimoto’s Disease, Graves’ Disease, rheumatoid arthritis, celiac disease and type 1 diabetes. If food that hasn’t been digested properly is able to leak through the lining of the intestines, it tells the immune system that it needs to produce antibodies and leads to the range of symptoms that characterize Leaky Gut Syndrome. The immune response can go far beyond the gut and it’s been suggested that it can be a big culprit in autoimmune disease in general.

It’s looking more and more likely that an unhealthy gut could be a major factor in autoimmune disease and that doing what you can to help your gut to heal could be highly beneficial for autoimmune disease. 

References:

1. https://hms.harvard.edu/news-events/publications-archive/brain/gut-brain#:~:text=The%20enteric%20nervous%20system%20that,brain%20when%20something%20is%20amiss.
2. https://www.parsleyhealth.com/blog/gut-microbiome-autoimmunity/#:~:text=There%20is%20a%20growing%20body,of%20an%20autoimmune%20disease%2C%20Dr.
3. https://www.ncbi.nlm.nih.gov/books/NBK279364/#:~:text=The%20main%20job%20of%20the,previously%20come%20into%20contact%20with.