Probiotics that broaden the mix of helpful bacteria in the gut may help to ease depression, say researchers.
Foods that broaden the profile of helpful bacteria in the gut are collectively known as probiotics. These "good bacteria" can be taken as supplements, or found naturally in yoghurts or fermented foods.
For the findings, the research team from the University of Brighton in the UK searched for relevant studies published in English between 2003 and 2019, which looked at the potential therapeutic contribution of pre-and probiotics in adults with depression and/or anxiety disorders.
Out of an initial haul of 71 studies, just seven met all the criteria for inclusion. All 7 investigated at least one probiotic strain; four looked at the effect of combinations of multiple strains.In all, 12 probiotic strains featured in the selected studies, primarily Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidium.
One study looked at combined pre-probiotic treatment, while one looked at prebiotic therapy by itself. The studies varied considerably in their design, methods used, and clinical considerations, but all of them concluded that probiotic supplements either alone or in combination with prebiotics may be linked to measurable reductions in depression.
And every study showed a significant fall or improvement in anxiety symptoms and clinically relevant changes in biochemical measures of anxiety or depression with probiotic or combined pre-probiotic use.
Of the 12 different probiotics investigated, 11 were potentially useful, the findings showed.'Probiotics may help reduce the production of inflammatory chemicals, such as cytokines, as is the case in inflammatory bowel disease, the researchers suggested.
"They may help direct the action of tryptophan, a chemical thought to be important in the gut-brain axis in psychiatric disorders," they added.
In this way, with a better understanding of the mechanisms, probiotics may prove to be a useful tool across a wide range of conditions," the authors wrote.