Does Probiotic Use Attenuate Depressive Symptoms?

However, study findings suggested that probiotics do not actually reduce depressive symptoms. Instead, dietary fiber emerged as being associated with lower odds of depression. The authors observe that dietary fiber is “now considered more than a static collection of indigestible plant materials.” Rather, it “provides substrates for bacterial fermentation,” thereby altering the composition of the gastrointestinal tract flora, and potentially improving the microbiome.

The authors point out that their study was limited in that the number of live microorganisms in a given probiotic has an impact on the effect of probiotics on a health outcome, and that they did not assess or control for the amount or types of bacterial strains in the foods or supplements that subject consumed. This limitation could “dilute” the strength of their findings.

Conclusion

While consumption of probiotics appears to be a promising avenue for reducing depressive symptoms, the authors conclude that their study does not bear out this association. The improvement in depressive symptoms that was found prior to adjustment for confounding factors may be attributable to better health and fewer risk factors for depression in subjects exposed to probiotics, vs those who were not.

References

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3.      Cepeda MS, Katz EG, Blacketer C. Microbiome-Gut-Brain Axis: Probiotics and Their Association With Depression. J Neuropsychiatry Clin Neurosci. 2016 Aug 19. [Epub ahead of print]

4.      Bravo JA, Forsythe P, Chew MV, et al. Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. Proc Natl Acad Sci U S A. 2011 Sep 20;108(38):16050-5.

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