Professor of the Practice of Law University of Denver Sturm College of Law

Prebiotic Supplements Improve Anxiety

Researchers are discovering that prebiotic and probiotic foods and supplements can improve some aspects of physical and mental health.  The focus is on the relationship between bacteria in the gut, brain function, and behavior.  There are neural, endocrine, and immune pathways that connect the gut and the brain, and these bidirectional information pathways are known as the gut-brain axis.  Gut microbial composition is influenced by diet and stress.

Probiotics are specific strains of bacteria that add to the population of healthy microbes in the gut.  Prebiotics are specialized plant fibers that stimulate the growth of healthy gut bacteria, much like a fertilizer.

Prior research has demonstrated that probiotics have reduced the stress hormone cortisol, and decreased sadness, distress, and depression.  Another study showed that a galacto-oligosaccharides (GOS) prebiotic, taken for 3 weeks, reduced cortisol and attention vigilance to negative information.

In a recent study of 48 healthy females, from 18-25 years, participants were given either a placebo or a galacto-oligosaccharides (GOS) prebiotic supplement (7.5 g) for four weeks.  The prebiotic group had 23 participants, and 12 were assessed as high anxiety and 11 as low anxiety.  The placebo group had 25 participants, with 13 as high anxiety and 12 as low anxiety.  Diets for all participants were consistent.  The prebiotic supplement reduced anxiety for the high anxiety group, but not the low anxiety group, when compared to the placebo group.  The prebiotic supplement also increased Bifidobacterium in the gut.

Prebiotic foods include garlic, onions, leeks, asparagus, bananas, beans, and chia.  Probiotic foods include yogurt, kefir, sauerkraut, kombucha, kimchi, and miso.

Takeaway: You may want to explore adding prebiotic foods and/or a prebiotic supplement to your diet if you suffer from anxiety. 


Nicola Johnstone et al., Anxiolytic Effects of a Galacto-oligosaccharides Prebiotic in Healthy Females (18–25 years) with Corresponding Changes in Gut Bacterial Composition, Sci Rep 11, 8302 (2021),

Mayo Clinic Staff, Prebiotics, probiotics and your Health, Mayo Clinic, Feb 27, 2021,

Debra S. Austin, Food for Thought: The Neuroscience of Nutrition to Fuel Cognitive Performance, 95 Or. L. Rev. 425, 470-471 (2017), online at

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