Graduation Year


Date of Submission


Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts



Reader 1

Gretchen Edwalds-Gilbert

Reader 2

Bethany Caulkins

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© 2022 Lateshia Peters


The gut microbiome’s critical functions in recent years have expanded beyond harboring a diverse community of microorganisms for pathogen protection and assisting in the processes of the digestive system. The gut-brain axis notion has been hinted at since Hippocrates' famous quote in 370 BCE: “All disease begins in the gut”. In recent years compelling research on digestive disorders such as irritable bowel syndrome (IBS) has contributed to further developing theories around the mechanisms by which bidirectional communication between the gut and brain occurs. This research has significant implications for how diet can directly impact the gut-brain axis through the gut microbiome. Studies have emerged describing therapeutic use of probiotics to alleviate mental health disorder symptoms like depression, anxiety, and schizophrenia. Diets across the world are influenced by the Western diet which is infamous for its incorporation of ultra-processed foods. Ultra-processed foods have been associated with serious health issues including metabolic syndrome. There is evidence that gut microbiome composition differs amongst the sexes which could lead to problems arising that are dependent on sex. It has yet to be explored how diets with high amounts of ultra-processed foods can impact mental health through the gut-brain axis in women. This proposed experiment will investigate connections between diet, the microbiome, and the brain using female germ-free mice as model organisms. We will first study how gut microbiome composition and functions are altered by ultra processed food consumption using DNA from fecal samples amplified by PCR and sequenced after. Then, we will observe how gut-brain axis communication is altered by the gut microbiome through reporting short-chain fatty acids (SCFA) levels with gas chromatography-gas spectrometry and 5-HTP levels with high-performance liquid chromatography. Finally, we will measure behaviors and chemical composition associated with depression and anxiety through light/dark box test, forced swim test, and sucrose preference test. We predict that this study will have significant implications for how highly processed diets have a greater impact on systems specifically within female animal organisms including the central nervous system (CNS) which in future research could be replicated in human women.

This thesis is restricted to the Claremont Colleges current faculty, students, and staff.