Probiotics, Stress and Behavior

Photo of lactobacillus bacteria

Research is mounting on how intestinal microorganisms such as probiotics may influence mood and behavior.

I attended an interesting virtual trade show on February 1, 2012. It was entitled “Pre- & Probiotics 2012” and was put on by Decision Media.

Globally, digestive or “gut” health is the benefit consumers most commonly associate with probiotics (i.e., beneficial organisms found in the gastrointestinal track) followed by awareness for their immunity benefits. Interest is also growing in how intestinal organisms, called intestinal microbiome or microbiota, may influence a person’s weight. However, a presentation during the virtual trade show by Dr. John Bienenstock, professor, Pathology and Molecular Medicine, McMaster University, Ontario, Canada, offered another potential benefit of probiotics.

A person’s microbiota may influence their cognitive health. In his presentation “Not just about gut health – The new wave in probiotics,” Bienenstock reviewed research and possible explanations behind how intestinal microbiota may impact nervous systems, which in turn influences pain perception, stress, anxiety and thus behavior. For example, Bienenstock reviewed a study where colicky babies were given a placebo or the probiotic L. reuteri (at levels of 10(8) per day). After three weeks, over 80% of the babies that had been given L. reuteri were less colicky while only 37% in the placebo group (the group not given the beneficial bacteria) improved(1).

Bienenstock also discussed studies(2,3). that showed that gut bacteria influenced anxiety levels in mice. How can you tell if a mouse is stressed out? When put in a box, a stressed and anxious mouse spends more time traveling along the walls of the box while “relaxed” mice spend proportionally more time in the center of a box “out in the open,” so to speak.

Much explanation was provided in how organisms found in the gut may impact mental health. For example, in recently published research(4). changes were found in the brains of mice that had been regularly fed a certain Lactobacillus strain (L. rhamnosus JB-1). Specifically, changes were found in the “expression of receptors for the neurotransmitter GABA.” GABA is an important inhibitory neurotransmitter in the nervous system of mammals and helps regulate neuron excitability. The research abstract concludes that “L. rhamnosus (JB-1) reduced stress-induced corticosterone and anxiety- and depression-related behavior.”

Bienenstock also covered research in which early gut infections caused behavioral abnormalities in mice. With very minor (that is, subclinical) infections with the bacteria Campylobacter jejuni, mice were more anxiety in mazes and they decreased their exploratory behavior(5). No doubt there may well be people jumping to conclusions and assume this can explain personalities, even behavioral problems, in humans. However, being able to say “Little Jimmy is shy because he had diarrhea as a baby” is a bit of a stretch…not that it won’t happen. See the Global Food Forums Blog “Rats are not Little People”.

Two other important points were made by Bienenstock in regards to probiotics. First, that any particular probiotic benefit cannot be related to all probiotics. Some to many benefits may be “strain specific.” This is good in that it provides reasons for companies to fund research. Secondly, in some research, probiotic organisms killed by heat or gamma radiation were as effective as live organisms. This result is likely music to the ears to many of the “virtual attendees” at “Pre- & Probiotics 2012,” a large portion who represented dietary supplement rather than food companies.

Claudia O’Donnell, Global Food Forums, a conference and seminar service

References:
(1) Savino, F, et al. 2010. Lactobacillus reuteri DSM 17938 in infantile colic: a randomized, double-blind, placebo-controlled trial. Pediatrics. 126(3):e526-33 http://pediatrics.aappublications.org/content/126/3/e526
(2) Sudo, N, et al. 2004. Postnatal microbial colonization programs the hypothalamic-pituitary-adrenal system for stress response in mice. J Physiol. 558(Pt 1):263-75. Epub 2004 May 7. http://www.sciencedirect.com/science/article/pii/S0531513105017395
(3) Heijtz, RD., et al. 2011. Normal gut microbiota modulates brain development and behavior. Proc Natl Acad Sci U S A. 108(7):3047-52. Epub 2011 Jan 31. http://www.pnas.org/content/108/7/3047.full
(4) Bravo JA , etal. 2011. Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. Proc Natl Acad Sci USA. 108(38):16050-5. Epub 2011 Aug 29 or http://www.pnas.org/content/108/38/16050
(5) Goehler, LE, et al. 2008. Campylobacter jejuni infection increases anxiety-like behavior in the holeboard: Possible anatomical substrates for viscerosensory modulation of exploratory behavior. Brain Behav Immun. 22(3):354-66. Epub 2007 Oct 24. http://www.sciencedirect.com/science/article/pii/S0889159107002152
Also see the following (full article posted on the web): Cryan JF and O’Mahony SM. 2011. The microbiome-gut-brain axis: from bowel to behavior. Neurog.astroenterol Motil. 23(3):187-92. doi: 10.1111/j.1365-2982.2010.01664.x. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2982.2010.01664.x/full

Posted on:February 6, 2012

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