Once upon a time, experts considered beneficial bacteria (probiotics) to be helpful in managing only physical symptoms and conditions, such as diarrhea, heartburn, and irritable bowel. The presence of these microorganisms in the gut environment have been shown to help restore balance to the intestinal tract and assist in keeping related functions running smoothly. Now a growing number of studies are indicating that mental health is among those related functions.
This line of thinking goes hand-in-hand with the growing evidence of the strong link between the brain and the gut, also known as the brain-gut connection or brain-gut axis. This involves the concept that there is constant communication and reciprocity between these two areas of the body and the effect they have collectively on our health.
Probiotics for mental health
The majority of the research thus far has looked at the impact of probiotics on the gut bacteria environment in animals, and the findings are promising. We have seen, for example, that providing probiotics to mice, which modified the bacteria in their gut, caused the rodents to be less anxious and lowered their levels of cortisol, a stress hormone.
Human study results also have demonstrated a significant relationship between beneficial bacteria in the gut and mental health. In a clinical trial involving 40 patients with major depressive disorder, for example, half were given a placebo and the other half took a probiotic supplement (Lactobacillus acidophilus, L. casei, and Bifidobacterium bifidum, 2 billion CFUs each) for eight weeks. At the end of the study, individuals who had taken the probiotic had significantly lower scores on a depression test when compared with placebo. The probiotic group also experienced other benefits, including significantly lower insulin levels, reduced systemic inflammation, lower insulin resistance, and a significant rise in the antioxidant glutathione.
In another study, a group of individuals with chronic fatigue syndrome were given a probiotic and anxiety symptoms were reduced. For two months, the patients in the double-blind, randomized study took either a placebo or 24 billion CFUs of Lactobacillus casei strain. At the end of the study, those who had taken the probiotic showed a significant decrease in anxiety symptoms.
Probiotics and the gut-brain connection
Researchers are delving deep into the mysteries and functions of the gut-brain axis and uncovering various relationships. For example, a new study entitled "Anxiety, Depression, and the Microbiome: A Role for Gut Peptides," the authors explain how the two-way communication between the brain and the gut is very much a cooperative effort of different systems, including the immune, endocrine, enteric, and autonomic nervous systems.
Despite this realization, however, there is still much to be learned about all of the interactions and how they affect mental and physical health. The authors noted that "Given the emerging role of the gut-brain axis in a variety of brain disorders, such as anxiety and depression, it is important to understand the contribution of bidirectional interactions between peptide hormones released from the gut and intestinal bacteria in the context of this axis."
These experts believe gut peptides are very significant in the regulation of brain-gut communication and they name names: for example, they call out neuropeptide Y, pancreatic polypeptide, peptide YY, corticotropin-releasing factor, oxytocin, and ghrelin, among others. These and other gut peptides play a significant role in brain-gut signaling in stress-related psychiatric conditions. Two examples are gut peptides that are known to bind with receptors on immune system cells and vagus nerve terminals, which enables indirect brain-gut communication.
Another way probiotics affect mental health may be through their ability to produce neurotransmitters, such as serotonin, gamma-aminobutyric acid (GABA), and acetylcholine. When these neurotransmitters are secreted in the gut, they may cause cells in the gut lining to release molecules that send messages to the brain and impact behavior.
Taking probiotics for mental health
So what does this mean for the average person? Maintaining a healthy balance of bacteria in the gut is paramount to good mental as well as physical health. To that end, daily supplementation with a high-quality and clinically proven probiotic is recommended.
[Editor's Note: Our partner Bio-K+ offers a 100% probiotic with proven benefits and effectiveness on human health. Bio-K's probiotic helps to maintain a healthy intestinal flora, support intestinal functions and activate the immune system. They have a wide range of products for your needs including fermented drinkable products for adults and children as well as capsules.]
Akkasheh G et al. Clinical and metabolic response to probiotic administration in patients with major depressive disorder: a randomized, double-blind, placebo-controlled trial. Nutrition 2016 Mar; 32(3): 315-20
Jade K. The best probiotics for mood: psychobiotics may enhance the gut-grain connection. University Health News 2017 Dec 7
Lach G et al. Anxiety, depression, and the microbiome: a role for gut peptides. Neurotherapeutics 2018 Jan; 15(1): 36-59
Pinto-Sanchez MI et al. Probiotic Bifidobacterium longum NCC3001 reduces depression scores and alters brain activity: a pilot study in patients with irritable bowel syndrome. Gastroenterology 2017 Aug; 153(2): 448-59
Rao AV et al. A randomized, double-blind, placebo-controlled pilot study of a probiotic in emotional symptoms of chronic fatigue syndrome. Gut Pathogens 2009; 1:6
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