It has been suggested that the gut microbiome is capable of influencing mood via the gut-brain axis. While inulin has demonstrated antidepressant and antianxiety effects in mice models of these conditions,[1][2] human clinical trials have found conflicting results. A 2019 meta-analysis of randomized controlled trials did not find an effect of prebiotics on anxiety or depression, although only four of the included trials used inulin and just one trial had a duration of at least 4 weeks.[3] Similar to other effects of inulin, some research suggests that inulin’s effect on mood depends on one’s baseline microbiome and health status.[4] Interestingly, a study in adults with mild-to-moderate anxiety and depression found that oligofructose supplementation increased the abundance of Bifidobacterium species, which was correlated with reduced scores (improved mood) on a variety of mood measurement tools; however, this study was funded and partially authored by a producer of oligofructose.[5] Ultimately, further research is needed to understand how inulin might impact mood.
Check out our summary of a 2021 study examining inulin’s effect on mood in people with obesity.