Jacquelin Stanberry

Background: Neuropsychiatric disorders with behavioral disturbances have been associated with gastrointestinal symptoms and altered gut microbiomes¹. The gut-brain axis is a bidirectional communication network with implications for health and disease that operates through three main pathways: immune, endocrine/systemic, and neuronal². The immune pathway communicates using inflammatory molecules, while the endocrine and neuronal pathways use hormones and neurotransmitters, respectively². These inflammatory molecules, hormones, and neurotransmitters are affected by the composition and diversity of the gut microbiome which has been recognized to be influenced by diet³. Current research is insufficient in demonstrating dietary influence on the bidirectional communication of the gut-brain axis. Understanding the mechanisms by which diet can alter the gut-brain axis is crucial in appreciating the implications for therapeutic innovation in neuropsychiatric disorders with behavioral disturbances.

Methods: The following search phrase was used in the PubMed database: ((microbiota-gut-brain axis AND (y_5[Filter])). Studies were selected based on relevance to dietary influences on gut microbiota and associated neurobehavioral outcomes.

Results: Dietary influence on the gut microbiome was demonstrated in an experiment showing participants consuming a vegetable-based diet had an increased abundance of Prevotella and Lachnospira in their gut microbiome compared to participants consuming an omnivore diet³. Further, a link between the gut microbiome and cognition was established with a study that found complex gut microbiomes in mice increased social behavior compared to mice with depleted gut microbiomes¹. Taken together, these studies suggest diet influences the gut microbiome which then can influence cognition. To further demonstrate this idea, one study found that irritable bowel syndrome (IBS) participants on restrictive/exclusive diets had different gut microbiome compositions compared to IBS participants on a standard diet⁴. The same study found that IBS patients were more likely to engage in restrictive/exclusion diets when compared to healthy controls⁴. Additionally, delivery of tannic acid-loaded nanoparticles to the gut improved microbial diversity, reduced brain inflammation, supported neural repair, and lowered systemic inflammatory markers – demonstrating the functional interconnectivity of the gut-brain axis⁵.

Conclusions: This review suggests that the gut-brain axis can be influenced by the diet altering the composition of the gut microbiome which may alter cognition and subsequent behavior. These insights may be leveraged to provide non-invasive and accessible therapeutic methods for treating neuropsychiatric disorders with behavioral disturbances. Further research should be directed towards identifying specific receptors and pathways of beneficial microbial metabolites so integration into therapies for these neuropsychiatric disorders is possible.

Works Cited

1. Wu, W. L., Adame, M. D., Liou, C. W., Barlow, J. T., Lai, T. T., Sharon, G., Schretter, C. E., Needham, B. D., Wang, M. I., Tang, W., Ousey, J., Lin, Y. Y., Yao, T. H., Abdel-Haq, R., Beadle, K., Gradinaru, V., Ismagilov, R. F., & Mazmanian, S. K. (2021). Microbiota regulate social behaviour via stress response neurons in the brain.
2. Wang Q, Yang Q, Liu X. The microbiota-gut-brain axis and neurodevelopmental disorders. Protein Cell. 2023;14(10):762-775. doi:10.1093/procel/pwad026
3. De Filippis F, Pellegrini N, Vannini L, et al. High-level adherence to a Mediterranean diet beneficially impacts the gut microbiota and associated metabolome. Gut. 2016;65(11):1812-1821. doi:10.1136/gutjnl-2015-309957
4. Lenhart, A., Dong, T., Joshi, S., Jaffe, N., Choo, C., Liu, C., Jacobs, J. P., Lagishetty, V., Shih, W., Labus, J. S., Gupta, A., Tillisch, K., Mayer, E. A., & Chang, L. (2022). Effect of Exclusion Diets on Symptom Severity and the Gut Microbiota in Patients With Irritable Bowel Syndrome.
5. He, H., Qin, Q., Xu, F., Chen, Y., Rao, S., Wang, C., Jiang, X., Lu, X., & Xie, C. (2023). Oral polyphenol-armored nanomedicine for targeted modulation of gut microbiota-brain interactions in colitis.