Here are some more articles that I found regarding psychobiotics or the use of probiotics to affect behavior and treat psychiatric disorders. A probiotic is a microorganism introduced into the body for its beneficial properties. Even though the articles are from 2013, they all give slightly different information about this emerging and exciting new field. Please note that psychotropic means having an effect on how the mind works (and it usually refers to drugs that affect a person's mental state). Remember that this area of research and terminology used is in its infancy. From Medscape (November 2013):
Probiotics, which are live bacteria that help maintain a healthy digestive system, are now often promoted as an important part of dietary supplements and natural food products. "Many of the numerous health-improvement claims have yet to be supported scientifically..."
They note that the term "psychobiotic" was created as recent studies have begun to explore a possible link between probiotics and behavior. "As a class of probiotic, these bacteria are capable of producing and delivering neuroactive substances such as gamma-aminobutyric acid [GABA] and serotonin, which act on the brain-gut axis," they write.
For this review, the investigators sought to examine studies that assessed whether ingesting these bacteria "in adequate amounts" could potentially lead to an effective treatment for depression and other stress-related disorders. In 1 of the preclinical studies examined, mice that ingested L rhamnosus showed reduced anxiety scores and "altered central expression" on both the GABA type A and type B receptors.
And a study of human patients with chronic fatigue syndrome showed that those who consumed an active strain of L casei 3 times a day had significantly higher improvement scores on anxiety measures than did those who received matching placebo. This provides "further support for the view that a probiotic may have psychotropic effects," write the researchers.
Still, Dr. Dinan called for caution. "What is clear at this point is that, of the large number of putative probiotics, only a small percentage have an impact on behavior and may qualify as psychobiotics," said Dr. Dinan. He added that for now, the field needs to wait for large-scale, placebo-controlled trials to provide definitive evidence of benefit and to detect which probiotics have psychobiotic potential.
Dr. Camille Zenobia wrote this in August 2013. From Real Clear Science:
But what about your brain? Apparently, bacteria influence what’s going on up there, too. Within the last several years, a blossoming field of study called “microbial endocrinology” has provided some provocative insights about the relationship between our GI microbiota and our mood and behavior.
Studies in the field of microbial endocrinology have implicated GI microbes as a factor that can regulate the endocrine system. This could have both good and bad effects since the endocrine system is responsible for the production of hormones and coordinates metabolism, respiration, excretion, reproduction, sensory perception and immune function.
From Nov. 2013 Popular Science:
The answer lies in the fact that many psychiatric illnesses are immunological in nature through chronic low level inflammation. There is a plethora of evidence showing the link between gut microbiota and inflammation and studies on probiotic strains have revealed their ability to modulate inflammation and bring back a healthy immunological function. In this regard, by controlling inflammation through probiotic administration, there should be an effect of improved psychiatric disposition.
The authors bring up another reason why psychobiotics are so unique in comparison to most probiotics. These strains have another incredible ability to modulate the function of the adrenal cortex, which is responsible for controlling anxiety and stress response. Probiotic strains, such as Lactobacillus helveticus and Bifdobacterium longum have shown to reduce levels of stress hormones and maintain a calmer, peaceful state. There may be a host of other probiotic bacteria with the same ability although testing has been scant at best.
Finally, the last point in support of psychobiotics is the fact that certain strains of bacteria actually produce the chemicals necessary for a happy self. But as these chemicals cannot find their way into the brain, another route has been found to explain why they work so well. They stimulate cells in the gut that have the ability to signal the vagus nerve that good chemicals are in the body. The vagus nerve then submits this information to the brain, which then acts as if the chemicals were there.