It often seems like our stomach has a mind of its own. In a sense, it does. Two layers of nerve cells run all the way through our digestive system, and make up what is called the “enteric nervous system” (ENS). Depending on the signals from this system, you can have a terrible time of irritable bowel syndrome (IBS) symptoms, or a calm day at the office.
That may be because 90 percent of serotonin, which we think of as a “brain chemical”, is actually created in the gut. Probiotics, the good bacteria that help us absorb nutrients from food, strengthen the immune system, and regulate digestion, can also interact with the chemical signals that travel from our enteric nervous system to our central nervous system, which has its headquarters in the brain.
Clinical studies and scientific research appear to bear out that at least at some level, probiotic balance in the gut does have an effect on states of mind. Some of this effect could be due to the probiotics’ overall effect in normalizing digestion so that the inflammation and irregularity of IBS is reduced. That alone is enough to make anyone feel better.
But the brain-gut connection is a complex arrangement, and researchers are still determining the exact mechanics of how they interrelate. In the meantime, selecting a quality probiotic that relieves overall gastric issues like bloating, diarrhea, constipation, or more serious episodes of intestinal conditions is simply going to help you feel better in mind and body regardless. While there are many supplements available, be certain to select probiotic blends that contain effective microbes, validated in human research.
McKean J, Naug H, Nikbakht E, Amiet B, Colson N. Probiotics and Subclinical Psychological Symptoms in Healthy Participants: A Systematic Review and Meta-Analysis. J Altern Complement Med. 2017;23(4):249-258.
Introduction/aim: Interest in the gut-brain axis and emerging evidence that the intestinal microbiota can influence central nervous system function has led to the hypothesis that probiotic supplementation can have a positive effect on mood and psychological symptoms such as depression and anxiety. Although several human clinical trials have investigated this, results have been inconsistent. Therefore, a systematic review and meta-analytic approach was chosen to examine if probiotic consumption has an effect on psychological symptoms.
Methods: The online databases PubMed, Scopus, and the Cochrane Library were searched for relevant studies up to July 2016. Those that were randomized and placebo controlled and measured preclinical psychological symptoms of depression, anxiety, and perceived stress in healthy volunteers pre and post supplementation with a probiotic were included. To control for differences in scales of measurement, data were converted to percentage change, and the standardized mean difference between the probiotic and control groups was investigated using Revman software. A random effects model was used for analysis. Heterogeneity was assessed using the I2 statistic. Quality assessment was undertaken using the Rosendal scale.
Results: Seven studies met the inclusion criteria and provided data for nine comparisons. All studies passed the quality analysis. The meta-analysis showed that supplementation with probiotics resulted in a statistically significant improvement in psychological symptoms (standardized mean difference 0.34; 95% confidence interval 0.07-0.61, Z = 2.49) compared with placebo.
Conclusion: These results show that probiotic consumption may have a positive effect on psychological symptoms of depression, anxiety, and perceived stress in healthy human volunteers.
Pirbaglou M, Katz J, de Souza RJ, Stearns JC, Motamed M, Ritvo P. Probiotic supplementation can positively affect anxiety and depressive symptoms: a systematic review of randomized controlled trials. Nutr Res. 2016;36(9):889-898.
Gastrointestinal microbiota, consisting of microbial communities in the gastrointestinal tract, play an important role in digestive, metabolic, and immune functioning. Preclinical studies on rodents have linked behavioral and neurochemical changes in the central nervous system with deficits or alterations in these bacterial communities. Moreover, probiotic supplementation in rodents has been shown to markedly change behavior, with correlated changes in central neurochemistry. While such studies have documented behavioral and mood-related supplementation effects, the significance of these effects in humans, especially in relation to anxiety and depression symptoms, are relatively unknown. Thus, the purpose of this paper was to systematically evaluate current literature on the impact of probiotic supplementation on anxiety and depression symptoms in humans. To this end, multiple databases, including Medline, PsycINFO, PubMed, Scopus, and Web of Science were searched for randomized controlled trials published between January 1990 and January 2016. Search results led to a total of 10 randomized controlled trials (4 in clinically diagnosed and 6 in non-clinical samples) that provided limited support for the use of some probiotics in reducing human anxiety and depression. Despite methodological limitations of the included trials and the complex nature of gut-brain interactions, results suggest the detection of apparent psychological benefits from probiotic supplementation. Nevertheless a better understanding of developmental, modulatory, and metagenomic influences on the GI microbiota, specifically as they relate to mood and mental health, represent strong priorities for future research in this area.
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