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Probiotics May Relieve Stress in Rats, But Not Humans

Probiotics May Relieve Stress in Rats, But Not Humans

New research finds evidence that probiotics can reduce anxiety in rodents, but not in humans.

University of Kansas investigators say that the benefits of probiotics continue to be under investigation. “I think people should wait — that’s the best takeaway here,” said lead author Daniel J. Reis, a doctoral student of clinical psychology at KU.

“We’re in the early days of this research into probiotics. I’ve seen a lot of stories hyping probiotics as helpful for anxiety. We’re not saying they do nothing, but we have a lot to figure out before we know if they can be used therapeutically. I wouldn’t recommend using probiotics to treat anxiety at this stage.”

The study, which reviewed research conducted on animals and people appears in PLOS ONE.

Reis and his KU colleagues Drs. Stephen S. Ilardi and Stephanie E.W. Punt reviewed data from 22 preclinical studies involving 743 animals and 14 clinical studies of 1,527 individuals.

The investigators determined “Probiotics did not significantly reduce symptoms of anxiety in humans and did not differentially affect clinical and healthy human samples.”

However, the researchers said their findings shouldn’t close the door on probiotics — the microorganisms in yogurts and other products that take up residence in our guts — as a potentially useful therapy for anxiety and other cognitive issues in the future.

“We see a lot of pathways between our digestive systems and our brains,” Reis said. “We see nervous system connections, the inflammation response — these microorganisms seem to be able to influence the human brain through this gut-brain axis.

We wanted to know if changes to the microbiota could improve mental health. But in terms of research, it’s all at a very preliminary stage.”

For example, Reis said rodents showing reduced anxiety after ingesting probiotics took a lot more probiotics than people in clinical studies, which could explain the difference in results.

“If you control for the weights of animals versus humans, animals are getting much larger doses of probiotics in these experiments by one or two orders of magnitude. Sometimes the doses were hundreds of times higher than we see in human studies,” he said.

“That’s something else we think is worth looking at.”

Co-author Ilardi also noted “there are thousands of different microbial species residing in the body, and they undoubtedly exert different effects on the brain. We even saw tantalizing hints in the rodent studies that some microbes may be particularly helpful in lowering anxiety, and we suggested that these probiotic strains might be particularly promising to study in future human trials.”

Also, the KU researchers pointed out that humans in the existing studies weren’t suffering from especially high levels of anxiety.

“We looked at clinical studies with people, and, in terms of the current literature, we didn’t find evidence that probiotics were reducing self-reported anxiety,” Reis said.

“But we noticed that none of the studies looked at individuals with clinically elevated anxiety. They weren’t looking specifically at anxious individuals. In terms of mental health applications for probiotics, those clinical populations haven’t been targeted yet.”

For people experiencing anxiety, Reis suggested reaching out for expert help.

“For anxiety, the number one thing is to seek professional treatment,” he said.

“That should be the first action — there are some good therapies out there that can help with various anxiety disorders. There are also helpful medications. These are the sort of things the people should do at this point to get help.”

Source: University of Kansas

Probiotics May Relieve Stress in Rats, But Not Humans

Rick Nauert PhD

Rick Nauert, PhDDr. Rick Nauert has over 25 years experience in clinical, administrative and academic healthcare. He is currently an associate professor for Rocky Mountain University of Health Professionals doctoral program in health promotion and wellness. Dr. Nauert began his career as a clinical physical therapist and served as a regional manager for a publicly traded multidisciplinary rehabilitation agency for 12 years. He has masters degrees in health-fitness management and healthcare administration and a doctoral degree from The University of Texas at Austin focused on health care informatics, health administration, health education and health policy. His research efforts included the area of telehealth with a specialty in disease management.

APA Reference
Nauert PhD, R. (2018). Probiotics May Relieve Stress in Rats, But Not Humans. Psych Central. Retrieved on November 30, 2020, from
Scientifically Reviewed
Last updated: 8 Aug 2018 (Originally: 23 Jun 2018)
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
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