Understanding What Probiotics Reduce Cortisol Levels

November 16, 2025 •

4 min read

Studies have shown that chronic stress can negatively alter the gut microbiome, impacting mood and inflammation. Probiotic intervention, particularly with specific strains, has emerged as a promising strategy to help reduce cortisol levels by modulating the communication between the gut and the brain.

Quick Summary

This article explores the specific probiotic strains, known as psychobiotics, that can help reduce elevated cortisol. It details the mechanisms involved, reviews scientific evidence supporting certain strains, and discusses how improving gut health can influence stress response and overall mental well-being.

Key Points

Specific Strains Reduce Cortisol: Clinical studies confirm that certain strains of Lactobacillus (e.g., L. plantarum 299v, L. helveticus R0052) and Bifidobacterium (e.g., B. longum 1714) can effectively lower cortisol levels.
The Gut-Brain Axis is Key: Probiotics influence mood and stress response via the gut-brain axis, a communication network connecting the gut microbiome to the central nervous system.
Multiple Mechanisms at Play: Probiotics lower cortisol by regulating the HPA axis, producing mood-stabilizing neurotransmitters like GABA and serotonin, and reducing systemic inflammation.
Strengthens Gut Barrier: By improving the integrity of the intestinal lining, probiotics prevent inflammatory triggers from entering the bloodstream that could spike cortisol.
Part of a Holistic Strategy: Probiotic supplementation is most effective when combined with other healthy lifestyle practices, such as stress management, regular exercise, and good sleep hygiene.
Evidence is Strain-Specific: The psychobiotic effects are not universal across all probiotic species; results depend heavily on the specific strain used, with targeted formulations often yielding the best results.

The Gut-Brain Axis: A Two-Way Street for Stress

The bidirectional communication network between your gastrointestinal tract and your central nervous system is known as the gut-brain axis. This complex system involves neural, endocrine, and immune signaling pathways, allowing gut microbes to directly influence brain function and mood. When you experience stress, your body activates the hypothalamic-pituitary-adrenal (HPA) axis, leading to the release of cortisol. In a state of chronic stress, this system can become overactive, causing persistently high cortisol levels and contributing to mood disorders and gut dysbiosis.

Certain probiotic strains, often called psychobiotics, can modulate this axis to lower cortisol by several key mechanisms:

Modulating the HPA Axis: Probiotics can help restore proper HPA axis function, inhibiting the overproduction of cortisol triggered by stress.
Producing Neurotransmitters: Specific bacteria can produce neurotransmitters like gamma-aminobutyric acid (GABA) and serotonin, which play a crucial role in regulating mood and stress.
Reducing Inflammation: Chronic stress and high cortisol are linked to increased inflammation. Probiotics can produce anti-inflammatory compounds, which helps break the cycle of inflammation contributing to stress and higher cortisol.
Strengthening the Gut Barrier: A “leaky gut” increases inflammation and stress. Probiotics strengthen the intestinal lining, preventing harmful substances from entering the bloodstream and triggering an inflammatory stress response.

Key Probiotic Strains for Cortisol Reduction

Clinical trials have identified several specific probiotic strains that show promise in lowering cortisol and improving stress-related symptoms. It's important to remember that the effects can be strain-specific, so not all probiotics in a genus will have the same impact.

Lactobacillus Strains

Lactobacillus plantarum 299v: A placebo-controlled trial found that administration of L. plantarum 299v reduced salivary cortisol levels in students during examination stress. This strain also has documented benefits for individuals with irritable bowel syndrome (IBS), a condition closely linked with stress.
Lactobacillus helveticus R0052: Studies involving a combination of L. helveticus R0052 and Bifidobacterium longum R0175 have shown reduced urinary free cortisol, as well as lower self-reported anxiety and depression scores in healthy subjects.
Lactobacillus rhamnosus: The strain L. rhamnosus (specifically JB-1 in animal studies) has been shown to reduce stress-induced corticosterone (the animal equivalent of cortisol) and modulate GABA receptors in the brain. While not all studies show identical results in humans, it remains a heavily researched psychobiotic.

Bifidobacterium Strains

Bifidobacterium longum 1714: Research from the APC Microbiome Institute found that healthy volunteers taking B. longum 1714 experienced reduced daily perceived stress and lower salivary cortisol levels compared to a placebo group. This strain appears to influence vagus nerve signaling, which connects the gut to the brain.
Bifidobacterium adolescentis: In addition to promoting overall gut health, some research indicates that certain strains of B. adolescentis may help reduce depressive- and anxiety-like behaviors by lowering inflammatory cytokines.
Bifidobacterium longum NCC3001: A randomized trial showed that intervention with B. longum NCC3001 reduced stress symptoms and improved sleep quality, with salivary cortisol levels being higher in the placebo group.

How to Incorporate Cortisol-Reducing Probiotics

Incorporating these helpful bacteria into your routine can be done through a few different avenues, including supplements and fermented foods. The best approach often depends on individual health goals and preferences. For targeted effects, supplements with clinically-studied strains are typically recommended.

Comparison of Key Psychobiotic Strains


Probiotic Strain	Primary Genus	Cortisol Reduction	Supports Mental Health	Supporting Evidence
L. plantarum 299v	Lactobacillus	Proven in human studies (salivary cortisol)	Reduces anxiety during stress	Randomized controlled trial
L. helveticus R0052	Lactobacillus	Proven in human studies (urinary free cortisol)	Reduces anxiety, depression, anger, hostility	Randomized controlled trial
B. longum 1714	Bifidobacterium	Proven in human studies (salivary cortisol)	Reduces perceived stress, improves mood, memory	Gold-standard randomized controlled trial
B. longum NCC3001	Bifidobacterium	Shown to reduce salivary cortisol	Improves sleep quality, reduces stress symptoms	Randomized, placebo-controlled trial

Conclusion: The Holistic Connection

The connection between the gut microbiome and stress management is undeniable and backed by a growing body of scientific research. Specific probiotic strains, particularly from the Lactobacillus and Bifidobacterium genera, have been identified as effective in helping to reduce cortisol levels and alleviate associated symptoms like anxiety and poor sleep. This effect is mediated through the gut-brain axis by modulating the HPA axis, reducing systemic inflammation, and influencing neurotransmitter production. While probiotics are a powerful tool, they are best used as part of a comprehensive stress-reduction strategy that also includes healthy diet, exercise, and adequate sleep. Ongoing research continues to uncover the full potential of these beneficial microorganisms, paving the way for more targeted and personalized therapies for stress and anxiety in the future. For more in-depth information on the interaction between gut microbiota and the gut-brain axis, read this review article on the National Institutes of Health website: The role of probiotics and prebiotics in modulating of the gut-brain axis.

The Holistic Connection

Frequently Asked Questions

Probiotics reduce cortisol by influencing the gut-brain axis. They can modulate the hypothalamic-pituitary-adrenal (HPA) axis, reduce inflammation, and help produce neurotransmitters like serotonin and GABA, all of which contribute to a calmer stress response.

Specific strains with clinical evidence for reducing cortisol or stress-related symptoms include Lactobacillus plantarum 299v, Bifidobacterium longum 1714, and the combination of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175.

The gut-brain axis is a two-way communication pathway between the gut microbiome and the brain. It can be disrupted by stress, leading to a feedback loop where stress harms the gut, and gut dysbiosis exacerbates the stress response, including higher cortisol.

While fermented foods like yogurt and kefir are great for general gut health, they often do not contain the specific, clinically studied strains at the effective doses needed to reduce cortisol. For targeted benefits, a high-quality supplement with documented strains is usually recommended.

Clinical trials show varying timelines, but some effects on mood and stress can be noticed within a few weeks of consistent use. Significant changes often require longer-term supplementation, from several weeks to months.

For most healthy individuals, probiotics are considered safe and well-tolerated. Some people may experience minor side effects like gas or bloating initially. However, individuals with compromised immune systems or other serious health conditions should consult a healthcare provider before use.

Yes, some probiotics can improve sleep quality, partly by balancing stress hormones like cortisol. The reduction in cortisol and anxiety can lead to a more relaxed state, which enhances the body's natural sleep-wake cycle.

Psychobiotics are specific probiotic strains that have been studied for their ability to influence mood, cognition, and stress response via the gut-brain axis. They are essentially probiotics with mental health benefits.