The "brain" in your gut can affect your mood

Your gut really does have a brain of sorts. It’s called the enteric brain and contains an extensive network of neurons—more neurons than in either the spinal cord or peripheral nervous system. Not only does your enteric brain handle digestion or inflict the occasional nervous pang, it partly determines your mental state and plays key roles in certain diseases. 

Your gut's brain is in constant contact with your head brain. About 90 percent the nerve fibers in your vagus nerve is carrying information from the gut to the brain and not the other way around. In fact, a big part of your emotions are influenced by nerves in your gut. Butterflies in your stomach is a simple example. But everyday emotional well-being may rely on the constant messages going from your gut brain to your head brain.

Ninety-five percent of your body’s serotonin is located in your bowels. Serotonin is a neurotransmitter and hormone that is involved in the transmission of nerve impulses and is key to mood regulation including feelings of happiness. Antidepressant medications called selective serotonin reuptake inhibitors (SSRIs) increase serotonin levels—but can also provoke gut issues such as irritable bowel syndrome. Too much serotonin may also play a role in osteoporosis. But too little can make you depressed. It’s quite tricky.

Recently, scientists have discovered that the microbes in your gut are important for the production of serotonin. In fact, the cells that produce serotonin depend on microbes to manufacture it. Researchers have found that changing gut microbes in mice alters their behavior. In one experiment, researchers were trying to pinpoint the causes of irritable bowel syndrome, which is often accompanied by anxiety and depression. By introducing fecal samples of people with IBS into the guts of germ-free mice, the mice began demonstrating symptoms of IBS, including anxiety.

I don’t know what you can do with this information. It just seems important to me.

For an introduction to this blog, see I Just Say No; for a list of blog topics, click the Topics tab.