How gut health affects your mood, and vice versa

Giving a speech or bidding on a house you really want might make you anxious.

And sometimes that nervous energy goes right to your stomach. You might feel nauseated, full or maybe more hungry than usual. That feeling in your stomach is not your imagination — your gut health is linked to your mood.

What lives inside your gut

By gut, I’m referring to the large intestine, one of the last organs your digested food goes through after you eat. Inside your large intestine, a storehouse of bacteria, viruses, fungi and other micro-organisms help process food you eat and have a lot of influence throughout your body. Most research ties the health of that bacteria in your gut to your mood.

The bacteria in your gut are constantly communicating with your brain, and vice versa. So having a healthy and diverse population of bacteria in your gut can help your mood.

Here’s why:

Neurotransmitters: Your gut bacteria and your brain produce and respond to the same neurotransmitters, chemical messengers that carry signals from one nerve cell to the next. A healthy gut is better able to produce and react to these chemical messengers, including serotonin and gaba, both of which can improve your mood.

Gut bacteria affect your immune system: Eating a lot of processed foods or sugar or experiencing a lot of stress can cause the cellular lining of your large intestine to lose its integrity. When that happens, parts of gut bacteria and other toxins can go into your bloodstream. A leaky gut can cause your immune system to react. If your immune system stays triggered, chronic inflammation can, over time, lead to diseases including depression, type 2 diabetes, heart disease and rheumatoid arthritis.

The vagus nerve is a critical nerve connecting your brain to your gut. It runs from your brain to your large intestines and controls your mood, digestion, how your immune system responds and your heart rate variability, the changes in time between each heartbeat. By releasing neurotransmitters, gut bacteria can send signals to the brain through the vagus nerve and can even influence your relaxation response.

How stress and diet affect the gut

Stress can affect what you eat. We think we control what we crave, but our gut bacteria can influence that. Certain bacteria survive on certain nutrients. That’s why when you’re anxious, you may crave sugar or comfort food — pizza, macaroni and cheese or cookies, all high in carbohydrates and saturated fat. It can be a vicious cycle in which the bacteria in your gut that sabotage your health trigger cravings for sugar and comfort food, the very food that leads those bacteria to thrive.

What you eat influences how healthy your gut is. The standard American diet is high in processed food, food that’s been changed from its natural state, often by adding salt, sugar and other substances to it. Highly processed food can trigger your immune system to send out cells to fight what’s considered an intruder. Constant triggering of your immune system isn’t healthy.

How do I reset or improve my gut health?

A healthy gut has a large and diverse population of different bacteria and other microorganisms. Over many decades in the United States, the typical microbiome has become far less populated and less varied. That’s because, on average, people are eating more sugar and processed foods than they did many decades ago.

When your gut doesn’t have a variety of bacteria and other microbes in it, there’s a greater chance for the bacteria, viruses and other organisms that cause disease to survive in your body and cause sickness.

The best food for your gut is fiber, a variety of fruits and vegetables and minimal amounts of processed foods, salt and sugar. Omega 3 fatty acids, which are found in walnuts, salmon, flax seeds and other foods are important as well. They can act as a buffer to stress by reducing chronic inflammation in your body.

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Can you cure depression by having a healthy gut?

That’s hard to say. There are many different types and causes of depression. Some research has shown that some people with depression also have chronic inflammation. By reducing that inflammation through a healthy diet and stress management, you may be able to reduce your risk of depression or ease your depression.

What is certain is that research showing the connection between the gut and your mood can open a lot of possibilities for treating mood disorders as well as diseases. One day, “psychobiotics” or supplements containing bacteria beneficial to your health may be used to help improve your mood. Gut bacteria outnumber human cells, so harnessing them for our benefit is a new and exciting frontier in psychology.