Probiotics not effective in alleviating anxiety

Consuming probiotics - live bacteria that are good for health - does not reduce anxiety in humans, a study has found.

The researchers from the University of Kansas in the US reviewed data from 22 preclinical studies involving 743 animals and 14 clinical studies of 1,527 individuals,

"Probiotics did not significantly reduce symptoms of anxiety in humans and did not differentially affect clinical and healthy human samples," said Daniel J Reis, a doctoral student and lead author of the study published in the journal PLOS ONE.

"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," Reis said.

 

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," said Reis.

"Sometimes the doses were hundreds of times higher than we see in human studies. That's something else we think is worth looking at," he said.

The 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," he said.

However, the researchers said their findings should not 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.