The gut and brain are connected in more ways than you might think. You can support your mental health by supporting your gut health.

Looking into the vast night sky, all the stars you can see on a clear night represent only the tiniest fraction of the number of microorganisms that live in your digestive system. Your gut is home to trillions of bacteria, fungi, and viruses.

When in balance, these microorganisms — collectively called your microbiome — contribute to mental health and almost every other function of your body. On the other hand, an imbalance has been linked to several health conditions, including those involving your mental health.

Your gut microbiome communicates with your brain along the vagus nerve — your body’s longest, most complex and influential nerve in your body. This communication system is called the gut-brain axis.

The microbes (microorganisms) that call your gut home are part of the enteric nervous system, which is sometimes called the “second brain,” from the 1998 book by Dr. Michael Gershon.

The trillions of microbes living in your gut affect many things, including your immune system and chemicals that affect your brain.

Research in 2017 suggests that an unbalanced gut microbiome may contribute to the development of a variety of mental health conditions.

Certain bacteria in the gut can also play a role in the body’s inflammation response, which may influence brain function. Some researchers believe inflammation may contribute to mental health conditions such as anxiety.

The research into how your gut and brain are connected is large and always evolving. Bacteriology (the study of bacteria) and fecal transplants have helped scientists investigate ways to use the microbiome to improve health.

This has given rise to a new field in psychiatry called nutritional psychiatry and emerging therapies like psychobiotics — aka using the microbiome to influence behavioral and mental health.

Gut issues that might be linked to mental health

Research in 2019 notes that imbalances in gut health have been linked to various mental health and central nervous system conditions, including:

Researchers have also looked into the connection between poor gut health and conditions of the bowel and gastrointestinal tract, which often coexist with mental health conditions. Some of these gastrointestinal (GI) conditions include:

A 2020 study suggests that changes in gut microbiota can disturb the two-way communication along the gut-brain axis, leading to depression. However, researchers still don’t know why this happens.

In other words: Do changes in gut microbiome cause depression, or does depression cause changes in the microbiome?

A 2018 study proposes that it’s a little of both: Certain gut microbes might contribute to depression, and depressive states might cause changes in gut microbes.

The neurotransmitter serotonin may also be involved.

An imbalance in serotonin levels has long been thought to contribute to depression. But most serotonin is not created in your brain — your gut produces more than 90% of the serotonin in your body.

Some research suggests that changes in the gut microbiome may influence serotonin production. More research is still needed to understand this connection better.

Research has explored a similar relationship between gut microbiome changes and anxiety.

Findings in 2017 indicate that life stressors can contribute to changes in the composition of the gut microbiome, which may influence anxiety disorders.

Diet is one of the most important ways to build a healthy gut microbiome. A research review in 2017 suggests that eating a variety of vegetables, whole grains, fish, and fruits is a good first step for improving gastrointestinal health.

To boost gut health, you can aim to consume the optimal amounts of certain nutrients, like:

Some research, like this 2019 study, suggests probiotic supplements may be a good way to restore microbiome balance.

If you want to learn more about foods that can help with stress, you can check out this list.

All the microbes in your gut are called the gut microbiome, consisting of bacteria, viruses, fungi, and other single-celled organisms.

These microbes act collectively to assist many body functions, including digestion, immunity, and mental well-being. Researchers believe that when your gut microbiome is out of balance, it can contribute to physical and mental health conditions.

Scientists and experts continue to learn more about the gut microbiome and ways to alter it to better improve our health.