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Healthy Gut = Happy Mind? The Gut's Role In Anxiety & Stress

Author:

Ava Durgin

March 21, 2025

Assistant Health Editor

By Ava Durgin

Assistant Health Editor

Ava Durgin is the Assistant Health Editor at mindbodygreen. She is a recent graduate from Duke University where she received a B.A. in Global Health and Psychology. In her previous work, Ava served as the Patient Education Lead for Duke Hospital affiliated programs, focusing on combating food insecurity and childhood obesity.

Image by Ana Luz Crespi / Stocksy

March 21, 2025

Anxiety is on the rise, affecting nearly 60 million adults in the U.S. and close to a billion people worldwide. While medications and therapy remain the primary treatments, an unexpected player in mental health is emerging: gut bacteria.

A new study published in EMBO Molecular Medicine suggests that these microscopic organisms may have a direct impact on brain function—specifically, anxiety levels—by regulating neuronal activity in a key fear-processing region of the brain.

The experiment: How gut bacteria influence anxiety

Researchers from Duke-NUS Medical School and the National Neuroscience Institute of Singapore conducted a preclinical study in mice to explore the gut-brain connection. They divided the mice into two groups:

Normal mice: These mice had a typical gut microbiome.
Germ-free mice: Raised in completely sterile conditions, these mice had no gut bacteria.

The results were striking: The germ-free mice displayed significantly more anxious behaviors than their normal counterparts.

When placed in an open-field test—a large box with both enclosed and open areas—the germ-free mice preferred hiding along the edges instead of exploring. In an elevated zero maze test, they spent less time in open sections, further confirming their heightened anxiety.

But behavior was just the beginning. The researchers examined the mice's brains and found that the basolateral amygdala—a region responsible for processing fear and anxiety—was hyperactive in germ-free mice.

Their brain cells were firing excessively due to impaired SK2 channels, which normally act as brakes on neuronal excitability.

The key to a calmer brain

To see if gut bacteria could restore balance, the researchers introduced indole, a compound naturally produced by gut microbes, into the germ-free mice's diet.

Remarkably, this simple addition reversed the brain hyperactivity and reduced their anxiety-related behaviors. The treated mice became more exploratory and exhibited activity patterns similar to normal mice.

This suggests that gut bacteria play an essential role in regulating anxiety by producing biochemical signals that influence brain function. In other words, gut microbes may act as natural mood stabilizers.

A potential breakthrough in mental health

This study offers strong evidence that the gut microbiome is directly linked to anxiety-related behaviors.

While it's still early-stage research (and in this case, done on animals), the findings open the door to potential new treatments for anxiety disorders in humans—ones that don't rely solely on traditional medications but instead target gut health.

Dietary interventions for more support

While gut dysbiosis may contribute to mental health challenges, certain foods can help restore microbial balance and support brain function. Here's what the research says about different dietary components:

Probiotics (live beneficial bacteria):

Certain probiotics—especially Lactobacillus and Bifidobacterium strains—may help reduce stress, anxiety, and depression.

For example, postpartum women who took Lactobacillus rhamnosus HN001 had fewer symptoms of anxiety and depression 1, while another study found that L. rhamnosus Probio-M9 improved stress resilience 2.

Prebiotics (food for gut bacteria):

Prebiotics, such as dietary fiber and galacto-oligosaccharides (GOS), can promote the growth of beneficial bacteria.

A study found that GOS supplementation helped reduce anxiety symptoms 3 in healthy females by increasing Bifidobacterium levels.

Synbiotics (probiotics + prebiotics):

Combining probiotics and prebiotics may offer even greater benefits.

One study found that a four-week synbiotic supplement increased levels of Lactobacillus and Bifidobacterium while improving mental health markers.

Fermented dairy products:

Yogurt, kefir, and other fermented dairy products naturally contain probiotics.

One study found that a fermented dairy drink with Lacticaseibacillus paracasei improved gut bacteria balance and reduced depressive symptoms 4, especially in people with digestive issues.

Spices with mental health benefits:

Certain spices contain bioactive compounds that may positively impact the gut-brain axis.

Curcumin (found in turmeric) has been shown to reverse gut microbiota imbalances associated with anxiety in mice.
Capsaicin (from chili peppers) may reduce depression-like behaviors 5 by promoting beneficial gut bacteria such as Ruminococcus and Prevotella.
Zanthoxylum bungeanum (a spice used in traditional medicine) has been linked to gut microbiota changes that alleviate stress-induced depressive symptoms.

Fruits & vegetables:

A study of over 5,800 Australian adults 6 found that higher fruit and vegetable intake was associated with better mental health. Another study suggested that fiber-rich produce helped reduce inattention in children with ADHD 7 by supporting a healthy gut microbiome.

The takeaway

Your gut microbiome isn't just about digestion—it plays a powerful role in brain function and mental health. Research shows that gut dysbiosis is linked to anxiety, depression, and bipolar disorder, but dietary choices can help rebalance the microbiome.

By incorporating probiotics, prebiotics, fermented foods, and anti-inflammatory spices into your diet, you may support both gut and brain health naturally.

While we still have much to learn about the gut-brain axis, one thing is clear: What you eat doesn't affect just your body—it shapes your mind too.