Everyone has feelings of unease, worry, and fear occasionally during their lives but for some people anxiety becomes a daily companion.
Anxiety is the most common mental health disorder in the western world, affecting 40 million adults In the U.S. alone. (1)
A common story you hear from people is that they never felt depressed or anxious until they started to have problems with their gut. Several years ago, the same thing happened to me.
In my late twenties, I managed to drive myself into a burnout by a combination of work stress, excessive wrestling training, and not enough rest. I began experiencing gut issues and feelings of prolonged anxiety shortly after that.
After experimenting with several supplements for anxiety, I learned that probiotics and prebiotics had the clearest positive impact on my mood. For some people, other supplements such as the herb ashwagandha or the amino acid L-Theanine may be effective in alleviating anxiety; but for me, it started to seem like the mental symptoms were originating from my gut.
The Importance of the Gut Microbiome
The exact cause of anxiety isn’t fully understood. Factors such as brain chemical imbalances, inherited genes, and traumatic experiences are traditionally cited as possible causes behind the unpleasant state of turmoil.
I would wager that, in addition to these, another common underlying reason for mental symptoms is related to the disturbances in the gut microbiome.
Our intestinal tracts are home to trillions of microorganisms such as bacteria, yeast, Archaea, and even parasites. These microbes perform numerous vital functions, from creating fatty acids and synthesizing vitamins to processing waste products.
Over the past few decades scientists have started to uncover the impact of beneficial and harmful bacteria on our general health and well-being. Multiple diseases have been linked to disturbances in the gut microbiota such as gastrointestinal disorders, diabetes, obesity, and mental illness. (2, 3, 4)
The link between the gut microbiome and the brain has been known to science for a while now. The bacteria residing in our intestinal tract are able to influence our minds through the nervous system, immune system, bloodstream, and hormones. (5, 6, 7)
What is the Difference Between Probiotics and Prebiotics?
Before we dive into how and why anxiety can be treated with prebiotics, let’s take a step back and quickly clarify what the difference is between prebiotics and the more well-known probiotics.
Probiotics are the actual live bacteria such as lactobacillus and bifidobacteria, which you can get from probiotic supplements or probiotic foods such as yogurt or sauerkraut.
Prebiotics are a special type of plant fiber found in various foods and food supplements. Even though prebiotics are often classified as carbohydrates they do not get digested or absorbed from the small intestine.
The prebiotic fibers travel undigested to the colon, where they feed the friendly gut bacteria without feeding bad microorganisms or pathogens.
Common types of prebiotic fiber:
- Galactooligosaccharide (GOS)
- Fructooligosaccharide (FOS)
- Resistant starch
Research and clinical trials have shown that all of these prebiotic types are able to increase the amount of beneficial bacteria in our digestive tract. Most noteworthy they promote the rise in the number of the important bifidobacteria species. (8, 9, 10)
GOS: The Most Powerful Prebiotic?
As science has started to uncover the importance of gut flora, the interest toward prebiotic studies has also increased. As I stated before, by definition, all of these different prebiotic fiber types promote the growth of beneficial gut bacteria. However, the prebiotics are not created equal.
In studies, GOS prebiotics have presented as the most efficient form to increase the number of bifidobacteria in the colon. This is important because the fermentation of bifidobacteria produces multiple vital compounds such as conjugated linoleic acid (CLA) and the short-chain fatty acids butyrate, acetate, and propionate. (11, 12)
In addition to GOS being to beneficial bacteria akin to pouring gasoline on a fire, these fibers seem to also inhibit the adherence of pathogens to the intestinal cell surfaces. This means that taking prebiotics can straight take out disease-causing bad bacteria away from our guts to be transported out in feces. (13)
The science on these prebiotic fibers is quite new and almost all of the studies done on GOS have been published during the past 10 years. Slowly, but at a steady growing pace, an impressive amount of health benefits have been discovered from GOS intake.
GOS has been found to:
- Significantly relieve IBS symptoms (14)
- Reduce the markers of metabolic syndrome (15)
- Prevent travelers’ diarrhea (16)
- Promote gastrointestinal health and immune response in elderly people (17)
- Increase the amount of intestinal bifidobacteria (18)
And yes, GOS prebiotics have also been found to be effective in treating stress and anxiety.
How can BAD gut bacteria cause anxiety?
I would be lying if I said that I fully understood the link between our gut microbiome and anxiety. But so would everyone else who would make that same claim. The science on the gut-brain connection is evolving all the time.
What scientists are starting to understand is that chronic mental and emotional conditions such as anxiety or depression are often symptoms of hidden underlying problems.
A growing body of evidence suggests that problems in the gut, often accompanied by chronic inflammatory response, are a big player in emotional disorders.
Some of the reasons how bad intestinal bacteria can cause anxiety:
a) Neurotransmitters: Certain gut bacteria can produce neurotransmitters such as dopamine, serotonin, norepinephrine, and GABA. These neurotransmitters can communicate with our brain through the nervous system and the tendrils of the vagus nerve, which connects our guts to our brains. (19)
b) Inflammatory response: Inflammation can always lead to increased secretion of the stress hormone cortisol which is connected to anxiety. Apart from causing actual inflammation in the digestive tract, nasty gut bacteria are also able to interact with the immune system, causing the release of inflammatory cytokines, which again leads to chronic stress response and anxiety.
c) Endotoxemia: Certain unwanted bacteria that may reside in our intestinal tract (e.g. E. coli) produce toxic lipopolysaccharide molecules which can travel through the gut wall into the systemic circulation. The translocation of these endotoxins causes an immune reaction, constant low-grade inflammation, and cortisol secretion.
This is also where prebiotics and probiotics come into play in dealing with anxiety. Prebiotics can affect all three factors I mentioned above.
- Prebiotics feed good bacteria, which can displace the microbial bandits that cause endotoxemia or produce anxiety-promoting neurotransmitters.
- Some bifidobacteria and lactobacilli species are known to produce GABA, an inhibitory neurotransmitter which has a calming and relaxing effect on the mind. (20)
- Prebiotic-fed bacteria such as lactobacilli and bifidobacteria can reduce inflammation and the inflammatory response, thus mitigating chronic stress states and anxiety. (21)
Probiotics and Prebiotics for Anxiety
Multiple human trials have shown that probiotics can affect mood and reduce anxiety or depression. (22)
The problem with—or a property of—probiotics is that the positive effects often last for only as long as you take them. The probiotic bacteria have positive immuno-regulating effects as they go through the intestines but usually they aren’t able to colonize or change the bacterial distributions in a permanent way.
Prebiotics are an interesting choice because they work as fertilizer for the good bacteria. With prebiotic supplementation, more significant and longer-lasting shifts can be achieved within the intestinal bacteria distribution. As the health writer Chris Kresser has said: You are what your bacteria eat.
More and more research is being done on prebiotics but they are not yet as much studied as probiotics. However, a couple of studies have presented the potential of prebiotics in anxiety treatment.
Studies on Anxiety and Prebiotics
A 2015 study from Oxford set out to test the efficacy of prebiotics in reducing anxiety. The researchers asked 45 healthy adults to take either a prebiotic or a placebo daily for three weeks. The prebiotics used in this study were GOS (Bimuno) and FOS. (23)
The results of the study were that the Bimuno GOS prebiotic supplement significantly reduced the sensations of anxiety. The researchers also found that GOS lowered the levels of cortisol—a stress hormone linked to anxiety—in the test subjects.
A little surprisingly, FOS prebiotics didn’t provide any anxiety relief in this study even though FOS is known to be able to promote bifidobacteria growth. This suggests that GOS is either a that much more powerful prebiotic or it provides additional positive effects besides being bifidogenic.
To date, this is the only human trial that has investigated the use of prebiotics for anxiety treatment. However, two new rodent studies give additional support to the understanding that prebiotics are indeed able to help with anxiety.
In a Colorado Boulder University study, the same GOS prebiotic improved sleep and recovery from stress in rats, and in another Oxford University experiment GOS was able to reduce endotoxemia-based anxiety and neuroinflammation in mice. (24, 25)
Conclusion on Prebiotics and Anxiety
One problem with treating anxiety is that it is hard to know what the real underlying cause for the mood disorder is. If the cause is an overgrowth of pathogenic bacteria or yeast in the gut, prebiotics might cure the whole disorder.
But, on the other hand, if the cause for anxiety—or depression—is, for example, a traumatic experience or a brain injury, the prebiotics might relieve the symptoms only temporarily or may not have any effect at all.
I tried several different probiotics and prebiotics when I had gut issues and was struggling with anxiety. I got the most relief from this GOS prebiotic and some bifidobacteria probiotics that I have written about previously.
I believe that prebiotic and probiotic foods and food supplements are a good remedy for anxiety and depression. They may be safer than conventional medication while providing additional health benefits. Still, if you are diagnosed with a disease or you are taking any medication you should consult your health care practitioner before trying out any new supplements.
A common saying is that People don’t change. My opinion is that it is actually rather easy to change a person.
Traditional belief about what makes a person is genes, environment, and experiences. I think it’s about time to add gut microbiome to that list. I hope I can write more about this topic later. The fact is that our personality, mood, and even interests in life can shift with changes in our bacterial distributions.
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The writer or writers of this blog are not doctors. The content in this blog is not meant to treat or diagnose any disease. If you make any changes to your diet or lifestyle, you do so at your own risk. Consult your doctor before making any changes to your lifestyle.