How do probiotics affect anxiety?
Taking probiotics can reduce anxiety in rodents. Researchers are now trying to find out whether such an intake can also help to reduce anxiety in people.
The University of Kansas scientists found in their current study that taking probiotics in mice can reduce anxiety. The study should now find out whether this effect can also be observed in humans. The doctors published the results of their research work in the medical journal "Plos One".
What are psychobiotics?
There is no clear indication that taking probiotics can help reduce anxiety in humans, although the new research shows that rodent anxiety is reduced, the experts explain. A wide range of diseases, from obesity to asthma, have been linked to the bacteria that live in our guts. A number of studies also indicate a connection to mood and behavior. As a result, there is growing interest in so-called psychobiotics: useful bacteria (probiotics) that also influence brain health via changes in the intestinal flora.
People with fear should seek professional help
When analyzing the results of previous studies, there was already evidence that probiotics appear to reduce anxiety in rodents. But there is little evidence that probiotics have similar benefits in humans, researchers add. If people suffer from anxiety, they should not rely on probiotics, the scientists explain. Affected people should definitely seek help professionally, there are various therapies available, adds study author Daniel Reis from the University of Kansas.
A total of 36 studies were evaluated
Reis and his colleagues examined 22 studies with a total of 743 rats and mice. In addition, 14 studies were analyzed in which a total of 1,527 people had participated. The doctors wanted to find out whether probiotics generally reduce anxiety.
Lactobacillus rhamnosus reduces anxiety in sick mice
Such a connection has been observed in sick rodents suffering from early life stress, infection or other specially induced impairments. However, such a connection could not be observed in healthy animals. The positive results in animals were consistently linked to one type of bacteria (Lactobacillus rhamnosus), although individual studies suggested that other species and strains could also have an anxiety-reducing effect. However, no positive effect was observed in humans when evaluating the studies, regardless of whether they were healthy or suffered from impairments such as cancer, irritable bowel syndrome or mood disorders, the scientists explain.
Do probiotics only help with severe anxiety disorders?
The researchers note that none of the retrospectively evaluated studies involved people with a diagnosed anxiety disorder. Probiotics may only help if certain anxiety states have already been reached, the doctors suspect. The fear experienced was also based on the participants' self-assessment and these assessments could have been unreliable. The follow-up may not have been long enough to determine all the effects, the doctors say. Before any conclusions are reached, it has to be tested how probiotics work in people with clinically significant anxiety, Reis adds.
More research is needed
The research team further explains that the doses of probiotics administered to rodents were up to 100 times greater than body doses relative to body weight. This suggests that experts should investigate whether the lack of effect observed in humans is at least partly due to insufficiently high doses. (as)