But, research analysis shows, potential link to reducing anxiety is not yet evident.
A study of the existing data, reported in BMJ Nutrition Prevention & Health, shows that probiotics taken either by themselves or when paired with prebiotics may help relieve depression.
But it’s not yet obvious if they will help relieve the fear, note the researchers.
Foods that expand the population of helpful bacteria in the intestine are commonly referred to as probiotics, whereas prebiotics are substances that help these bacteria survive.
There is a two-way connection between the brain and the digestive tract, defined as the gut-brain axis. And in recent years, the possibility that the microbiome – the range and number of bacteria residing in the gut – might help to treat mental ill health has become a focal point.
To further investigate this, the researchers searched for appropriate findings conducted in English between 2003 and 2019, which explored the possible therapeutic effect of pre-and probiotics in adults with depression and/or anxiety disorders.
Out of an original 71-study stack, only 7 meet all inclusion requirements. All 7 tested at least 1 probiotic strain; 4 looked at the impact of several strain combinations.
Over total, the chosen experiments included 12 probiotic types, mainly Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidium. One research analyzed mixed pre-probiotic therapy, whereas one looked at prebiotic therapy alone.
The research differed considerably in nature, methodology utilized, and therapeutic criteria but all of them concluded that probiotic supplements may be related to significant depression reductions either alone or in tandem with prebiotics.
And each analysis reported a substantial decrease or increase in symptoms of anxiety and/or clinically related improvements in biochemical anxiety and/or depression measurements with probiotic or pre-probiotic usage combined.
For the 12 main probiotics tested, 11 were theoretically beneficial, the results showed.
To their review , the researchers point out several caveats: none of the included studies lasted very long; and the number of participants in each was small.
This makes it impossible to draw some concrete conclusions regarding the cumulative benefits, if they are long-lasting, and whether any unintended side effects correlated with extended usage may arise, they add.
But they recommend additional research on the basis of the limited findings to date, non- and probiotic treatment needs additional study.
The researchers propose that probiotics may help reduce the development of inflammatory chemicals, such as cytokines, as is the case with inflammatory bowel diseases. Or they may help guide the activity of tryptophan, which is a chemical thought essential in mental conditions in the gut-brain axis.
Since anxiety disorders and depression impact individuals so differently, they are suggesting they need therapeutic strategies that take such nuances into consideration.
“In this way, with a better understanding of the mechanisms, probiotics may prove to be a useful tool across a wide range of conditions,” they write.
Individuals with depression and/or anxiety problems also have other psychological factors as well, they find out, such as decreased hormone development and irritable bowel syndrome.
“As such, the effect that probiotics have on patients with [common mental disorders] may be twofold: they may directly improve depression in line with the observed findings of this review, and/or they might beneficially impact a patient’s experience of their [common mental disorder] by alleviating additional comorbidities,” they write.
“Purely from the information gathered for this review, it is valid to suggest that, for patients with clinically recognized depression: isolate, or adjuvant prebiotic therapy is unlikely to affect an individual’s experience of their condition in a quantitatively evident way; and that isolate or adjuvant, probiotic/combined prebiotic-probiotic therapy may offer a quantitatively measurable improvement in parameters relating to depression,” they conclude.
“However, there are inadequate data to suggest anything meaningful to support or refute the use of either pre/probiotic agents (or a combination of both) in patients with clinically recognized anxiety disorders; this would be a useful area to investigate further.”