Feeling down? Probiotics may help ease depression, study finds

New research suggests that probiotics alone or combined with prebiotics, compounds that help probiotics flourish, may help ease symptoms of depression. To look at how probiotics and prebiotics could potentially be used to treat depression, UK researchers reviewed seven existing studies that examined the effects.

Probiotics are live bacteria that are known to supply health benefits when present in the human gut. The term probiotic applies to bacteria that is naturally present or external supplements. While prebiotics are carbohydrates and fibres that feed the beneficial bacteria in our gut. Humans don’t normally digest prebiotics directly.

The findings, published on Monday in the journal BMJ Nutrition Prevention & Health, showed that probiotics either taken by themselves or when combined with prebiotics may help to ease depression. But whether they may also help to reduce anxiety isn’t yet clear, researchers said.

They also found probiotics may help reduce the production of inflammatory chemicals, such as cytokines, as is the case of inflammatory bowel disease. The researchers pointed out that people with depression and/or anxiety disorders often have other underlying conditions, such as irritable bowel syndrome.

However, the researchers said their review had several caveats: None of the included studies lasted very long; and the number of participants in each was small. This made it difficult to draw any firm conclusions about the overall effects, how long they lasted and whether there might be any unwanted side effects with prolonged use.

“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,” the researchers say.

“Purely from the information gathered for this review, it is valid to suggest that, for patients with clinically recognised 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 quantitatively measurable improvement in parameters relating to depression.

“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 recognised anxiety disorders; this would be a useful area to investigate further.”

Probiotics can be found in a number of foods including yoghurt, kefir, kombucha, sauerkraut, pickles, sourdough bread and some cheeses.