The benefits of prebiotics for mental health: Can feeding your gut microbiome improve mood?

Along with numerous health benefits, prebiotics have the ability to support mental health.

There are many studies backing up the claim that prebiotic supplements can help reduce anxiety in some people. This, while at the same time helping the gut microbiome. 

Anxiety can be experienced in your day-to-day life with external stressors. In fact, anxiety disorders are considered one of the most common mental illnesses that affect over 40 million adults. Ironically, despite the spike in the rate of anxiety of disorders over the years, there is only 36.9 percent of sufferers get anxiety treatment.

Gut health helps mental health 

Mental treatments can be inaccessible for some individuals. The good news is that simply eating prebiotics can help improve mental health, particularly in relieving anxiety. 

By thinking about it, brain and gut health are two entirely different systems that function separately. However, in reality, both of these systems work closely together by exchanging hormonal, immune and nervous signals.

The gut microbiome, or an ecosystem of microorganisms that live in the human gut. It has a significant role in the relationship.

Reduce symptoms of depression

Surprisingly, prebiotics can positively impact depression. In animal studies, researchers suggest that a lowered significant amount of diverse gut bacteria or a high number of disease-causing species can lead to depression in mice [1].

Meanwhile, there is also some evidence claiming that probiotics – which are introduced as friendly bacteria in the gut – may improve symptoms of depression [2]. 

The benefits of prebiotics for mental health: Can feeding your gut microbiome improve mood?

Help cope with stress

Moreover, there are some research studies proving that prebiotics may help otherwise healthy individuals cope with stress and reduce milder cases of anxiety disorders. 

One example is a 2014 study that found a type of prebiotic supplement helpful in reducing the production of stress hormones called cortisol and improving emotional processing skills in healthy adults. The prebiotic supplement used in the research is called galactooligosaccharides (GOS) [3]. 

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Reduce anxiety levels 

Having anxiety is known to affect a person physically from head to toe. However, this mental disorder is entirely centered on the brain.

The most interesting part is that there is also a significant amount of evidence about the intimate connection between the things happening in the brain and in your gut.

Psychologists at the University of Surrey in Guildford have studied the benefits of galactooligosaccharides prebiotics (GOS) in the long-term mental health of adolescent females who are transitioning to adulthood. GOS is commonly found in dairy products, beans and certain root vegetables.

It is known that the transition from adolescence to adulthood is the key developmental stage in determining one’s ability to regulate emotions. This includes fear and anxiety [4]. 

In another research published by Scientific Reports [5], the researchers also found that prebiotic supplementation can lower anxiety in people with the highest trait anxiety levels.

Furthermore, they found a small but notable increase in the amount of a genus of bacteria called Bifidobacterium in the gut among the research participants. This explains the relationship between prebiotics and anxiety disorders. 

How to fine-tune the gut-brain axis? 

In animal studies, psychologists reported that adolescence is a crucial time for gut microbiota, and it is the perfect time to help fine-tune the gut-brain axis. 

The psychologists have tested the hypothesis with the hope of further extending the case to humans. They involved 64 healthy female volunteers aged 18 to 25 years [5].

Moreover, the researchers ensured that the participants had/were: 

  • No present or previous medical record and diagnoses of anxiety
  • Not taking any prebiotic or probiotic supplements
  • Not using antibiotics for the previous three months before the research undertaken 


The psychologists asked the participants to take either a GOS supplement or a placebo for four weeks. 

Also, the participants had to fill out a set of standard questionnaires to evaluate anxiety, depression, mood and emotional regulation abilities at the beginning and end of the study period. 

Along with the mentioned, the researchers also performed an attentional dot-probe task. This refers to a test of one’s emotional bias toward positive or negative stimuli.

Additionally, the participants gave their stool samples at the start and end of the study. The researchers assessed any changes in the makeup of their gut microbiota through their stool samples. 

Among the 64 participants who started the study, only 48 people were able to complete it.


At the end of the study, there were no visible effects of the prebiotic supplement on self-reported anxiety levels, which were biased toward positive emotional stimuli in the dot-probe task or the abundance of helpful gut bacteria.

On a different note, certain interesting trends began to show when the researchers divided the participants into high and low-anxiety groups, depending on their self-reports at the start of the study. 

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From there, it was found that there were reductions in anxiety for the high-anxiety group who took GOS in comparison with the ones in high anxiety group that took the placebo.

Moreover, the participants in the high anxiety group showed a decreased bias to negative stimuli and an increased bias to positive stimuli in the dot-probe task. Plus, they also had significantly greater increases in the abundance of Bifidobacterium in their gut.

Prebiotics, probiotics and synbiotics for overall mental health

Another study was conducted focusing on the effects of a high-prebiotic diet compared with taking probiotic supplements and synbiotics on the mental health of adults. 

In the preliminary evidence, health experts support the utilization of dietary interventions and gut microbiota-targeted interventions, including probiotic or prebiotic supplementation, to improve mental health. Hence, the researchers thought of finding the most effective among the three variables: high-prebiotic diet, probiotic supplements and synbiotics. 

The benefits of prebiotics for mental health: Can feeding your gut microbiome improve mood?
Photograph: Prostock-studio/Envato

The study was conducted for 8 weeks involving 119 adults with moderate psychological distress and low prebiotic food intake. 

Treatment arms:

  • Probiotic group – probiotic supplement and diet-as-usual. 
  • Prebiotic diet group – high-prebiotic diet and placebo supplement.
  • Synbiotic group – probiotic supplement and high-prebiotic diet. 
  • Placebo group – placebo supplement and diet-as-usual. 

The main outcome was derived from the assessment of total mood disturbance after eight weeks, and the secondary outcomes involved measures for anxiety, depression, stress, sleep and well-being. 

At the end of the study, the researchers concluded that a high-prebiotic dietary intervention might enhance mood, anxiety, stress and sleep in adults with moderate psychological distress and a low amount of prebiotic intake. 

Also, a synbiotic combination of a high-prebiotic diet and probiotic supplement does not show a beneficial effect on mental health outcomes. However, the researchers urge further study as the results are limited by the relatively small sample size.

The gut and brain are closely connected

Following the research studies above, the gut microbiota, or various microorganisms like bacteria in the gut, can wield an important contribution to your brain’s function and behavior. 

When the composition of your gut microbes changes because of several factors, like shifts in your diet, lifestyle adjustments or even increased stress, the changes may negatively affect how your brain is operating.

It is found that a decrease in microbial diversity may lead to psychological changes that are associated with mental illnesses. Also, having high pathogenic microbes, or disease-causing bacteria, in the gut may inflict the same.

In fact, a 2010 research study showed that chronic gastrointestinal inflammation is caused by anxiety-like behavior [6], and the results in a 2014 research review [7] led researchers to think that changes in the gut microbiome may contribute to anxiety and other mental health conditions, including depression. 

These research studies separately evaluated the effects on the brain from several factors, such as changes to gut bacteria and gut inflammation of the brain, and both suggested discovering an association between the gut and anxiety.

Taking prebiotic supplements for mental wellness

With the findings from research studies revolving around the gut and brain, they help solidify the primary connection between the two important body functions. 

Taking prebiotic supplements regularly is found to reduce anxiety levels, and people may benefit from taking them to support their overall mental well-being. 

While probiotics provide live organisms and strains of bacteria that add to the good microbes that are present in your gut, prebiotics is more similar to fertilizers, on the other hand. When taken, prebiotics can stimulate and boost the growth of good bacteria in your gut.

As we unravel the close relationships between the gut and brain, it is wise to keep tabs on your gut health to positively impact your mental health as well. 


  • Surprisingly, there is an intimate, two-way line relationship between the gut and the brain, which is called the gut-brain axis.
  • The composition of your gut microbiota (or the diverse community of microorganisms living in the gut, whether good or bad) can affect mood, which is also linked to anxiety and depression.
  • As the composition of your gut microbiota affects some brain functions, taking prebiotics, which feed “friendly” bacteria in the gut, can aid in relieving depression in healthy adults.
  • One notable study in clinical trials in humans backed up the claim and suggested that a type of prebiotic may also lower anxiety in some females in late adolescence through changes in the gut microbiota.
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