9 Science Backed Benefits Of Probiotics For Depression

Shruti Baikerikar

(B.E. Biotechnology, PG Clinical Research)
Independent Researcher, Health Writer & Founder of Salubrainous [Full Bio]

probiotics for depression

Name: Probiotics, Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium bifidum
Number of scientific references: 44
Level of Evidence: Level III What is this?

Note:Probiotics are proven to reduce depressive symptoms within 3-8 weeks of therapy. They help normalize gut flora, balance stomach health and relieve anxiety like symptoms. Inclusion of probiotics in diet can be an effective strategy for preventing depression.

The benefits of probiotics in depression and other mental health conditions may have received scientific attention in the recent years, but its origin and history date the back to the early 1900s.

A really good read on this is Intestinal microbiota, probiotics, and mental health: from Metchnikoff to modern advances: Part I – autointoxication revisited by Bested et.al. It is kind of remarkable as to how physicians in 1860s explored mental health disorders as a ‘self-infective’ or ‘autointoxication’ process.

Improper digestion and harmful chemicals derived from intestinal bacteria were linked with poor mental health.

Microbes present in our gut aid in digestion, synthesis of vitamins, metabolism of toxins and boosting immune function. These microbes interact with our brain as well via vagal afferent nerves, HPA axis, production of metabolically active substances, etc. However, this interaction is bi-directional.

This pretty much explains why we experience butterflies in our stomach before an interview or exam or why we feel low on the days where our digestive system is disturbed, and we refer to it as ‘upset stomach.’

Various animal studies demonstrate that lack of proper gut micro flora can induce anxiety like behavior. Studies in humans as well, suggest that gut micro flora is imbalanced in depression. Consumption of probiotics can thus help in depression as they help to normalize gut micro flora and hence they have been appropriately named as ‘psychobiotics.’

What are probiotics?

Probiotics are the opposite of antibiotics; they nourish bacteria instead of killing them. However, the bacteria in probiotics specifically nourish good bacteria in the gut and promote health. Probiotics originate from Greek words that mean ‘for life.’

Bacteria present in probiotics are found naturally in fermented foods like yogurt, kefir, sauerkraut, etc. Probiotics are functional foods that have a higher concentration of these good bacteria.

The commonly used bacterial strains in probiotics are Lactobacilli and Bifidobacterium.

Probiotics primarily displace bad bacteria from the gut and improve digestion. They help boost immunity, reduce gut inflammation and protect from infection.

As they normalize gut health, they restore balance in gut brain axis and hence relieve mental health related symptoms.

Suggested Probiotic Supplements For Depression

Please consult a health practitioner before taking any health supplements.

Various strains are found to be beneficial for relieving depressive and anxiety symptoms and at this stage there is not sufficient research to develop personalized probiotic products for each individual.

The Lactobacilli and Bifidobacterium strains have been actively researched upon and the results are positive. VSL#3 is a pharmaceutical probiotic formulation (Buy from Amazon) that has been used in research studies and users find it helpful.

Here are a few multiple strain probiotic products that are optimized to resist stomach acid.

Hyperbiotics PRO-15 Nature’s Way Primadophilus Optima Naturenetics Flora Pro-Health Vegan Probiotic

Image Credit: Hyperbiotics

Image Credit: Nature’s Way

vegan probioticImage Credit: Naturenetics, Inc.
Provides 5 Billion CFU per capsule

Contains 15 probiotics strains and prebiotic fructooligosaccharides with patented time release technology

Provides 30 Billion CFU per capsule

Contains 14 probiotics strains and prebiotic fructooligosaccharides, enteric coating veg capsules

Provides 30 Billion CFU per capsule

Contains 5 probiotic strains per veg capsule

Suitable for vegetarian and vegan

Buy from Amazon

Buy from iHerb

Buy from Amazon

Buy from iHerb

Buy similar from Amazon

Buy similar from iHerb

9 Science Backed Benefits of Probiotics For Depression

Probiotics are being explored as an adjuvant therapy for depression for their multiple therapeutic benefits, few of which are enlisted below.

1. Probiotic consumption is proven to reduce depressive symptoms

Fermented foods have a number of health benefits, and this has been proven by science. A longitudinal study conducted in Spain observed the risk of depression in individuals who consumed yogurt (a source of probiotics) and prebiotics (like fructans and galactooligosaccharides).

Prebiotics, unlike probiotics, do not contain microbes but they have fibers that serve as food for healthy gut microflora.

They observed 14,539 men and women who did not have depression for 9.3 years. 727 individuals developed depression at the end of the study period.

It was observed that those who consumed whole fat yogurt had reduced depression risk. The risk was lowest for highest intake (more than seven servings a week) and increased as the intake of yogurt reduced. This association was more pronounced in women.

Also, this association was not found with low-fat yogurt consumption. Scientists are investigating why the fat content of yogurt affects brain and gut health. It is kind of clear that inclusion of natural dairy sources of probiotics is great for mental health (avoid in case of lactose intolerance).

Akkasheh et al. have proven by their study that eight-week supplementation of multi species probiotics reduces depressive symptoms in patients with Major Depressive Disorder as evidenced by decreased Beck Depression Inventory total scores.

Bambling et al. examined the effect of probiotics in treatment resistant depression, and their findings have been published in Inflammopharmacology, 2017.

12 individuals with treatment resistant depression were treated with probiotics/magnesium orotate supplement in addition to SSRIs. After 8 weeks, eight individuals experienced a significant reduction in depressive symptoms. A reduction in gut inflammation was observed.

However in the 16 weeks follow up, it was observed that despite continuing SSRI treatment, patients relapsed after probiotic supplementation was stopped.

Interestingly a recent study published in The Australian and New Zealand Journal of Psychiatry, 2017 found no therapeutic benefit of probiotic supplementation in low mood or depression. But the study had a couple of limitations with regards to the study population.

The study by Cepeda et al. published in The Journal of Neuropsychiatry and Neurosciences, 2017 have found that probiotics use is not associated with lower rate of depression in the national sample assessed by them.

This study is associated with Janssen Research and Development (part of Johnson-Johnson). One of the study limitations is that exposure to probiotics was defined as ‘having consumed any probiotic food or supplement on any of the interview days.’

The first review study on the effect of probiotics on depression by Huang et al. reported that probiotic intake reduced depression related scores significantly and their consumption affects both healthy and depressed individuals.

Their findings also suggested that this effect was more pronounced in individuals below 60 years of age. They suggested that probiotics can be a potential preventive strategy against depression.

A recent review study published in Journal of Alternative and Complementary Medicine, 2017 also confirmed that probiotic intake has a positive effect on psychological symptoms in depression and reduces stress in healthy individuals.

Quick Gist: Clinical trials demonstrate the probiotic consumption is effective in reducing depressive symptoms in Major Depressive Disorder and stress in healthy individuals. A few studies do not agree with this.
However recent review and meta-analysis study have taken into account quality clinical trials and concluded that probiotics help in significant reduction of depressive symptoms and can help prevent depression.

2. It protects metabolic health in depression

A study published in Nutrition 2016 demonstrated that probiotics intake is associated with reduced depression and improved metabolic health. This is the only study to examine this point, as per my knowledge.

40 individuals with major depressive disorder were involved in this study. They received either probiotic supplements or placebo for 8 weeks.

After 8 weeks, those who received treatment had reduced depressive symptoms compared with placebo. A decrease in insulin levels and reduced insulin resistance was observed in the probiotic group. The increase in levels of antioxidant glutathione and reduction in inflammatory parameters were also observed.

No differences in glucose levels, beta cell function, insulin sensitivity, lipid profiles, and total antioxidant capacity levels were observed.

The bacteria used were Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum.

Quick Gist: Probiotic supplementation is found to improve metabolic health modestly in addition to reducing depressive symptoms. It reduces inflammation, improves antioxidant levels and reduces insulin resistance.

3. Probiotic intake may reduce negative thoughts and prevents depression

It is kind of difficult to describe anxiety in few words, but it is somewhat an overflow of unreasonable negative thoughts. Anxiety and depression cage an individual in a vicious cycle.

This study published in Brain, Behaviour, and Immunity, 2015 demonstrated that probiotic consumption could reduce negative thoughts. Heightened response to a sad mood is considered as a marker of vulnerability to depression as per science.

So the scientists designed a study where the assessed the effect of probiotic consumption on response to a sad mood. 20 healthy individuals (who did not have mood disorders) were given a supplement with multi species probiotics while other 20 were given a placebo. The study lasted for 4 weeks.

It was observed that those who consumed probiotics compared to the placebo group were less sensitive to sad mood, and this was due to reduced rumination (overthinking) and aggressive thoughts. Scientists concluded that probiotic supplementation might help prevent depression.

Quick Gist: Probiotic supplementation in healthy individuals was found to reduce cognitive reactivity to low and sad moods. A reduction in aggressive, negative thoughts were observed as well as rumination was reduced. Dietary intake of probiotics may boost mental health and prevent depression.

4. It regulates and normalizes gut brain axis

The gut-brain axis is a bi-directional communication between the intestines and the brain. Gut microbes can produce neurotransmitters like serotonin and GABA which affect mood.

Disturbances in gut-brain axis have been noted in schizophrenia, autism, depression, and anxiety.

A study in animal model revealed that dietary administration of probiotics could have a positive influence on the gut-brain axis.

The treatment improved levels of BDNF (a brain protective growth factor), increased activity of genes related to serotonin (a neurotransmitter that is essential for optimum brain function) and it also improved gut microflora.

Similarly, Smith et al. also proved that probiotics could normalize gut-brain axis independent of immune system activity.

Quick Gist: Gut-brain axis dysfunction is observed in depression. Probiotics supplementation helps to restore and normalize gut-brain axis thus relieving depressive symptoms. Studies in animal model suggest that probiotics can even affect the genes associated with neurotransmitter production.

5. It reduces gut and systemic inflammation

The intestines form a very important line of defense against infections. The inflammation of the gut can lead to systemic inflammation and affect immune function.

Also, inflammation of the gut is also linked with the development of depression as secretion of inflammatory agents can affect brain function.

Probiotics have natural anti-inflammatory property, and they help alleviate gut inflammation. Their intake also alleviates other inflammatory disorders that may occur with depression like inflammatory bowel disease or arthritis.

Experimental studies reveal that probiotics reduced intestinal inflammation and regulated immune function which in turn impacts brain’s chemistry and behavior.

A study published in Journal of Neuroscience, 2015 demonstrated that probiotic intake reduces sickness associated with systemic inflammatory disorders. And inflammation is one of the important markers of depression. ( To learn more about the role of inflammation in depressive disorder please read Understanding Depression)

Quick Gist: Probiotics help reduce gut and systemic inflammation. Reduction in inflammatory agents helps improve brain function which in turn benefits in depression.

6. Probiotic consumption relieves stress and anxiety

Anxiety and chronic stress can affect a healthy human. And anxiety is that unwanted friend who always accompanies depression.

Findings from animal studies on probiotics and anxiety are promising. Here are a couple of mechanisms by which they fight anxiety:
• Prevent stress induced changes in brain’s plasticity
• Normalize HPA axis (a communication between major hormone producing glands and the brain)
• Support neurogenesis or formation of new nerve cells
• Reduces levels of stress hormones
• Normalizes neurotransmitter levels
• Improve cognition

Bifidobacterium, a type of probiotic bacteria, is found to reduce anxiety as effectively as escitalopram or Lexapro. Lactobacillus also regulates neurotransmitters to relieve anxiety.

A study published in Nutritional Neuroscience, 2016 demonstrated that consumption of probiotic supplement or yogurt helped reduce depression and anxiety scores in petrochemical workers.

A group of Japanese researchers has found that consumption of fermented milk containing Lactobacillus casei helps in reducing pre-examination stress and anxiety in students.

Quick Gist: Probiotic consumption helps reduce anxiety symptoms by regulating the HPA axis and reducing the levels of stress related hormones.

7. It protects stomach health

Gastric symptoms are very pronounced in major depressive disorder in a few individuals. This could involve bloating, constipation, diarrhoea, loss of appetite or even food intolerance.

Certain conditions may co-occur with depression like irritable bowel syndrome. Probiotics help in relieving colicky abdominal pain and symptoms like bloating, flatulence in IBS.

They also help in reducing symptom severity in IBD.

Diop et al. conducted a study where individuals facing stress were treated with probiotic preparation for 3 weeks. The treatment reduced stress induced gastric symptoms like abdominal pain and nausea/vomiting.

Quick Gist: Probiotic consumption relieves stress related gastric symptoms in depression.

8. It regulates neurotransmitter levels to alleviate mood disorders

Gut bacteria are actively involved in the development of neuro active molecules like GABA, serotonin, acetylcholine, etc. Probiotics are appropriately known as ‘psychobiotics’ as they increase the number of bacteria that produce these neuro active molecules.

Bifidobacteria increase the levels of tryptophan which is a precursor to serotonin (a neurotransmitter whose appropriate secretion is said to alleviate depressive symptoms). Similarly, lactobacilli also increase serotonin and dopamine levels.

Messaoudi et al. conducted a study to assess the psychotropic effects of probiotics in animal model and humans.

In an animal model, the treatment helped in reducing anxiety. In healthy humans, a reduction in depressive symptoms, anxiety, anger, and improvement in problem-solving was observed.

Tillisch et al. demonstrated that fermented milk consumption twice daily for 4 weeks by healthy women affected their brain activity related to the processing of emotions and sensations, positively.

Quick Gist: Experimental studies reveal that probiotic intake normalizes neurotransmitter levels in depression. Studies in humans demonstrate the probiotic intake is associated with a positive change in brain activity.

9. They strengthen antioxidant defense to protect brain health

Reduced intake of dietary antioxidants fuels oxidative stress in depression. Increased levels of oxidative stress affect brain function. (Read Understanding Depression to know how oxidative stress exacerbates depression)

Various probiotic strains have natural antioxidant property and can prevent/control diseases that are caused by oxidative stress.

A study published in Journal of Medical Microbiology, 2015 demonstrated that certain probiotics strain reduced oxidative markers in the brain and increased levels of antioxidant enzymes and neurotransmitter levels. This resulted in a neuroprotective effect.

Quick Gist: Probiotics raise the antioxidant defenses in the brain to protect it from neurodegenerative diseases and mental health disorders.

Dosage of Probiotics For Depression

There is no specific dosage of probiotics for depression that has been outlined. It depends on the type of bacteria and product involved.

For lactobacilli, the dosage may be in the range of 1-20 billion colony forming units per day. For yeast, the dose is 250-500 mg.

Harvard Health Publications reports the recommended dosage is 1-10 billion colony forming units (1-2 capsules) several days per week.

The studies we have explored above utilize a multispecies probiotic supplement containing 2 billion colony forming units of each bacterium.

Probiotics can be obtained from foods as well such as yogurt, kefir, sauerkraut, soy drinks, tempeh, etc.

Consult a health practitioner before taking probiotics supplements.

Precautions with Probiotics Use

Probiotics are safe for consumption. The most common adverse effect associated with probiotic consumption is gastric side effect such as bloating, constipation, diarrhoea, etc.

However, these side effects are transient. If these symptoms get severe, reduce the dosage and consult a health practitioner as well.

A few precautions to be noted regarding probiotic use:
• Avoid in case of weakened immunity, taking immunosuppressants or chemotherapy
Avoid in case of risk of developing D-lactose acidosis (bowel surgery or short gut syndrome
• Avoid if taking sulfazines or antibiotics
Avoid if you have artificial heart valves
• If susceptible to allergies, consult a health practitioner before taking probiotics.

Please consult a health practitioner before taking probiotic supplement especially if on other medications.

Conclusion: Do probiotics help with depression?

Based on the data reviewed above, it can be concluded that probiotics help significantly in reducing anxiety, fear and emotional reactions to low mood. The course action ranges between 3-8 weeks of daily intake.

Also, they ensure a healthy gut and scientists suggest that probiotics can help in the prevention of depression.
Coming to a personal experience, I have not faced any adverse interactions with probiotics and antidepressants. But I do maintain 3-4 hour gap between consuming the two.

Probiotics have helped me significantly to get rid of gastric symptoms associated with depression. Also, they have helped me relieve anxiety and fear like symptoms significantly after 3-4 days of consumption. I opt for a milk based drink of probiotics and have found it awesome for gut health.

Have probiotics helped you relieve depression related symptoms? Do leave your comments below.

Probiotics consumption reduces anxiety and improves mood in depression.


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