In our busy modern lives we humans are becoming more distant from our natural world more than ever. We are now starting to see the consequences of living a such stressful lives, and even in these testing times our first instinct is towards problematic synthetic solutions.
However, even modern pharmaceuticals follow the traditional pathways of the natural world, and that includes those prescribed for anxiety and depression. However, is it possible to relieve these symptoms and other health problems by promoting our internal balance instead of introducing drugs or synthetic substances?
Medical treatments for acute health problems have had impressive success because they do what is expected in these situations. They shut down the symptoms temporarily. However, even modulating sources of physical and emotional pain does not reduce the incidence of chronic non-communicable diseases, including arthritis, hypertension, and mental health problems such as anxiety and depression.
Recently in the field of probiotics there has been a search for a solution to various ailments, including mental health problems. In their search, investigators have found that there’s a link between our gut health and the way our brain works. Impressively and quite unexpectedly, it is possible to modulate the way our brain works and how different parts connect with each other by triggering modifications in our gut microbiota. How does it work?
About anxiety, depression, and our gut microbiota
Our modern understanding of the human body combined with what we formerly knew about the brain has shed light to a new association: that of the brain and the gut microbiota.
For example, we can start talking about serotonin, which is a substance synthesized and secreted in the central nervous system. There are other neurotransmitters in the brain, including noradrenaline and the inhibitor transmitters GABA. An imbalance of these neurotransmitters is associated with symptoms of anxiety and depression, and recent science has uncovered that serotonin is not only synthesized by the central nervous system. Our gut shares a significant role in maintaining its balance as well.
Thus, the intestinal function plays a fundamental part in the regulation and elaboration of serotonin. Moreover, other substances in our diet and an imbalance in our gut microbiota may create changes to our gut metabolism and impair the normal secretion and release of serotonin. This will not only have consequences in our gut but also our central nervous system.
Consequently, scientific literature points out that people who suffer from anxiety disorders and depression often have an intestinal dysbiosis. Their pathogenic gut microbiota is significantly increased at the expense of the healthy bacteria. Studies also show a pattern of bacteria that may not be causing gastrointestinal alterations but are commonly found in higher proportions in patients with anxiety and depression.
How probiotics modulate brain activity
The association between probiotics and brain activity may seem quite difficult to understand if we think about these systems as entirely separate and independent units. But as we have shown above, they are not. The nervous system is deeply connected with the human gut, and there’s a gut-brain axis of continuous information that connects gastrointestinal and mental health together.
Probiotics are microorganisms normally encountered in our gut microbiota. They can be found in many forms of fermented foods or probiotic supplements. When they are in contact with your gut, they favor colonization of a particular bacterial strain over the other, and since they will be competing for space in the intestinal lumen, they will slowly take the place of harmful bacteria.
The exact mechanism still remains elusive, but many different trials have reported changes in stress responsiveness, brain biochemistry, pain perception, and the regulation of anxiety and mood. The major changes are usually associated with one of the following changes:
- An improvement in inflammation, which affects not only the gut but the chemistry of the brain as well.
- Changes in the concentration of neurotransmitters in the brain, especially serotonin, which is actively produced in the human gut.
- Improvements in the response to stressful stimuli, which improves anxiety and prevents depression.
Promising clinical studies about probiotics and the gut-brain axis
The connection between the gut and the brain is not only a theory, and it is not only based on studies performed in rats and animal models.
Recent studies have evaluated these claims in patients with depression and anxiety, showing that there’s a definite connection, and we can extrapolate the results of animal models in humans as well. For example, a study performed in 2017 reported a significant improvement in irritable bowel syndrome along with the reduction of depression symptoms in patients receiving strains of Bifidobacterium longum.
Another study tested the application of probiotic supplements for 8 weeks in patients with significant depression and reported that at the end of the study they had significantly lower scores of depression, and their quality of life had improved considerably.
This is a promising alternative treatment for patients with mild depression symptoms, especially if they have gastrointestinal problems as well. They would avoid adverse effects from antidepressants, which include addiction, sleep disturbances, and increases in cardiovascular risk. Still, it is essential to highlight that cases of significant depression might require medication and psychotherapy in conjunction with probiotics in order to improve their quality of life.
Is probiotics the future treatment for anxiety and depression?
Even though we still have an incomplete understanding of how probiotics modulate brain activity, it is undeniable they do. And science always starts by wondering why things happen as they do. We don’t currently know how, but futures studies may elucidate biochemical and physiologic pathways. When that happens, we will be able to provide targeted treatments according to each pathology by using harmless probiotics without any unexpected side effects.
Until then, we do know which probiotic strains are apparently associated with a significant improvement in depression symptoms. They are:
- Bifidobacterium spp., especially B. longum, B. bifidum, and B. infantis.
- Lactobacillus spp., especially L. plantarum, L. reuteri, and L. helveticus.
We can find those in greek yogurt, by adding pickles to your burger, adopting new foods to your diet such as sauerkraut and kimchi, or by simply using probiotic supplements containing one of these strains.
Romijn, A. R., Rucklidge, J. J., Kuijer, R. G., & Frampton, C. (2017). A double-blind, randomized, placebo-controlled trial of Lactobacillus helveticus and Bifidobacterium longum for the symptoms of depression. Australian & New Zealand Journal of Psychiatry, 51(8), 810-821.
Evrensel, A., & Ceylan, M. E. (2015). The gut-brain axis: the missing link in depression. Clinical Psychopharmacology and Neuroscience, 13(3), 239.
Wallace, C. J., & Milev, R. (2017). The effects of probiotics on depressive symptoms in humans: a systematic review. Annals of general psychiatry, 16(1), 14.
Akkasheh, G., Kashani-Poor, Z., Tajabadi-Ebrahimi, M., Jafari, P., Akbari, H., Taghizadeh, M., … & Esmaillzadeh, A. (2016). Clinical and metabolic response to probiotic administration in patients with major depressive disorder: a randomized, double-blind, placebo-controlled trial. Nutrition, 32(3), 315-320.
Pinto-Sanchez, M. I., Hall, G. B., Ghajar, K., Nardelli, A., Bolino, C., Lau, J. T., … & Traynor, J. (2017). Probiotic Bifidobacterium longum NCC3001 reduces depression scores and alters brain activity: a pilot study in patients with irritable bowel syndrome. Gastroenterology, 153(2), 448-459.
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