Which Probiotics Reduce Cortisol to Alleviate Stress?

October 5, 2025 •

5 min read

Chronic stress, a pervasive issue, can lead to elevated cortisol levels, impacting mood, sleep, and overall health. Emerging research into the gut-brain axis reveals that specific probiotic strains, sometimes called "psychobiotics," can help to manage this stress response and reduce cortisol production. This guide explores the scientific evidence behind which probiotics reduce cortisol and the underlying mechanisms involved.

Quick Summary

This article examines specific probiotic strains proven to help lower cortisol levels and mitigate stress. It details how certain Lactobacillus and Bifidobacterium strains can influence the gut-brain axis, reduce inflammation, and boost mood-regulating neurotransmitters.

Key Points

Specific Strains Reduce Cortisol: Clinical studies have shown that certain strains, known as 'psychobiotics', can lower cortisol levels, particularly Bifidobacterium longum 1714 and Lactobacillus plantarum 299v.
Gut-Brain Axis Modulation: Probiotics work by influencing the bidirectional communication network between the gut and the brain, helping to regulate the body's stress response via the HPA axis.
Multiple Mechanisms: Their effects involve several pathways, including reducing systemic inflammation, strengthening the gut barrier, and supporting the production of mood-regulating neurotransmitters like GABA and serotonin.
Multi-strain Formulas Are Effective: Combinations of specific Lactobacillus and Bifidobacterium strains, such as L. acidophilus Rosell-52 and B. longum Rosell-175, have been shown to reduce both psychological distress and physiological markers of stress.
Holistic Approach is Best: For optimal results, supplementing with cortisol-reducing probiotics should be paired with other lifestyle changes, including a healthy diet rich in fiber, regular exercise, and adequate sleep.

Understanding the Gut-Brain Axis and Cortisol

To understand how probiotics can reduce cortisol, it's essential to grasp the concept of the gut-brain axis. This is a bidirectional communication system linking the central nervous system (CNS) with the enteric nervous system (ENS) of the gastrointestinal tract. This connection involves neural, endocrine, and immune pathways. The gut, often called the "second brain," contains an intricate ecosystem of microbes that influence the brain's function and behavior, including stress and mood.

Cortisol is a steroid hormone released by the adrenal glands as part of the body's 'fight or flight' stress response, controlled by the hypothalamic-pituitary-adrenal (HPA) axis. While a necessary function for survival, chronic stress leads to overactivation of the HPA axis and sustained high cortisol levels, which can negatively affect immune function, gut integrity, and mental health. Probiotics, when introduced into the gut, can modulate the gut-brain axis to help regulate the HPA axis and bring cortisol levels back into balance.

Specific Probiotic Strains That Reduce Cortisol

Research has identified several specific probiotic strains with promising effects on stress and cortisol reduction. These strains, often found in the Lactobacillus and Bifidobacterium genera, are sometimes referred to as 'psychobiotics' for their beneficial impact on mental health.

Bifidobacterium longum 1714 (B. longum 1714)

This specific strain has been the subject of dedicated research for its psychobiotic properties. A randomized, double-blind, placebo-controlled study with healthy volunteers found that those taking B. longum 1714 reported lower perceived daily stress and reduced salivary cortisol levels compared to the placebo group. The mechanism is thought to involve influencing vagus nerve signaling, a crucial communication pathway between the gut and the brain. Further neuroimaging studies showed that B. longum 1714 modulated brain activity related to stress response and emotion processing.

Lactobacillus plantarum 299v (L. plantarum 299v)

Clinical research involving students undergoing examination stress showed that daily consumption of Lactobacillus plantarum 299v prevented the typical increase in salivary cortisol levels seen in the placebo group. This indicates the strain's ability to stabilize the HPA axis response during acute stress. The study concluded that this probiotic has the capacity to keep cortisol levels in check during stressful periods.

Combination Strains

Some of the most compelling evidence comes from multi-species probiotic formulations that demonstrate synergistic effects. One combination that has shown efficacy includes Lactobacillus acidophilus Rosell-52 and Bifidobacterium longum Rosell-175. A trial involving volunteers showed that this combination supported mental well-being and reduced stress and anxiety levels. Another multi-species blend, which included Bifidobacterium longum and Lactobacillus helveticus, was shown to reduce urinary free cortisol levels in human subjects.

Mechanisms Behind Cortisol Reduction

Probiotics don't just magically reduce cortisol; they work through several interconnected pathways that comprise the gut-brain axis. These mechanisms highlight the complexity of the gut's influence on the brain and the body's stress response.

Modulation of the HPA Axis: By interacting with the vagus nerve and immune system, probiotics can influence the activity of the HPA axis, which regulates cortisol production. This helps normalize the body's stress response, preventing the excessive release of cortisol during stress.
Reduction of Systemic Inflammation: Chronic stress and high cortisol levels are linked to increased inflammation. Some probiotics reduce this inflammation by producing anti-inflammatory compounds and strengthening the gut barrier, which prevents toxins from entering the bloodstream and triggering an immune response.
Neurotransmitter Production: Gut microbes are capable of producing and regulating key neurotransmitters that impact mood and stress, such as serotonin, dopamine, and gamma-aminobutyric acid (GABA). These neurotransmitters help regulate emotions and can indirectly lead to a calmer HPA axis and lower cortisol.
Improved Gut Barrier Integrity: Stress can increase intestinal permeability, also known as "leaky gut". This allows inflammatory substances to pass into the bloodstream, triggering systemic inflammation and heightening the stress response. Probiotics help fortify the gut barrier, reducing this permeability and the subsequent inflammatory and cortisol-raising effects.

Comparison of Key Cortisol-Reducing Probiotic Strains


Feature	Bifidobacterium longum 1714	Lactobacillus plantarum 299v	Multi-strain Combination (e.g., L. acidophilus R0052, B. longum R0175)
Research Evidence	Strong evidence in human trials; shown to reduce perceived stress and salivary cortisol.	Proven to prevent stress-induced cortisol increases in human trials during academic exams.	Multiple clinical studies support its efficacy in reducing stress, anxiety, and urinary cortisol.
Primary Mechanism	Modulates vagus nerve signaling to the brain, influencing HPA axis activity.	Stabilizes the body's stress response system, normalizing cortisol levels during acute stress.	Likely works through multiple synergistic pathways, including HPA axis modulation and neurotransmitter regulation.
Best for	Individuals experiencing chronic daily stress and seeking overall improved mood and vitality.	Those facing short-term, acute stressors like exams or major life events.	A broader approach for individuals with various stress symptoms, including anxiety and GI issues.
Source/Availability	Often available in specific psychobiotic supplement formulas.	Found in targeted probiotic supplements; commercially available.	Available in many commercially formulated probiotic blends, often marketed for mood or stress support.

Combining Probiotics with Lifestyle Strategies

While specific probiotic strains can be a powerful tool for managing cortisol, their effects are maximized when combined with other stress-reducing lifestyle strategies. A holistic approach that addresses the multiple factors contributing to high cortisol is most effective.

Diet: A diet rich in prebiotic fibers, found in foods like onions, garlic, bananas, and oats, provides fuel for beneficial gut bacteria. Consuming fermented foods like yogurt, kefir, and kimchi can also naturally introduce probiotics.
Exercise: Regular, moderate-intensity exercise has been shown to reduce cortisol levels and improve mood.
Sleep: Aim for at least 7 hours of quality sleep per night. Sleep is essential for regulating cortisol levels and supporting the body's repair processes.
Mindfulness and Relaxation: Practices like meditation, deep breathing, and yoga can help calm the nervous system and decrease stress hormones.
Omega-3 Fatty Acids: These fatty acids have anti-inflammatory properties and may help balance cortisol.

Conclusion

Research continues to solidify the link between gut health and mental well-being via the gut-brain axis, with certain probiotic strains emerging as a promising avenue for naturally managing stress. Specific strains, particularly from the Lactobacillus and Bifidobacterium genera, have demonstrated the ability to reduce elevated cortisol levels in clinical trials. These psychobiotic effects are mediated through mechanisms that include modulating the HPA axis, reducing inflammation, improving gut barrier integrity, and influencing neurotransmitter production. While supplementation with targeted probiotic strains shows significant promise, combining them with a healthy diet, regular exercise, and sufficient sleep offers the most comprehensive strategy for supporting a balanced stress response and reducing cortisol. For those with persistent stress or suspected high cortisol, seeking guidance from a healthcare professional is recommended to determine the best approach. A healthy gut is a key component of a resilient and calm mind.

Authoritative Outbound Link

For more detailed scientific information on how specific probiotic strains affect the gut-brain axis and psychological functions, the National Institutes of Health (NIH) provides extensive research. National Institutes of Health (NIH) | (.gov)

Frequently Asked Questions

The gut-brain axis is a communication system linking your gut microbes with your brain. It influences your HPA axis, which controls stress hormones like cortisol. Probiotics can help regulate this communication, leading to a more balanced stress response.

The timeline can vary individually, but research suggests that noticeable effects on stress and cortisol levels can occur within 4 to 6 weeks of consistent probiotic intake.

No, the effects are strain-specific. While many probiotics benefit gut health, only certain strains, often referred to as psychobiotics, have demonstrated effects on the gut-brain axis and cortisol regulation in clinical studies.

Fermented foods like yogurt, kefir, and kimchi contain probiotics, but the specific strains and quantities required to significantly impact cortisol are more reliably found in specialized probiotic supplements. A balanced diet, however, supports a healthy gut microbiome.

Probiotics are generally safe, but some individuals may experience minor digestive side effects, such as gas or bloating, as their gut adapts. Those with compromised immune systems should consult a doctor before use.

Dosage varies depending on the specific strain and product. It's best to follow the instructions on a high-quality supplement that specifies the psychobiotic strains used and has been studied for its effects. Consult with a healthcare professional for personalized guidance.

Both single-strain and multi-strain probiotics can be effective, depending on the specific strains included. Some multi-strain formulations are designed to be synergistic, while studies on specific single strains have also shown significant results.