Date of Award:

5-2025

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Nutrition, Dietetics, and Food Sciences

Committee Chair(s)

Korry J. Hintze

Committee

Korry J. Hintze

Committee

Robert E. Ward

Committee

Stephan van Vliet

Abstract

We investigated the impact of protein source in a western-style diet on colon cancer, colitis, and the gut microbiome. The Western dietary pattern is energy-dense, low in fiber, and has a sub-optimal micronutrient profile. Our group has formulated the Total Western Diet (TWD) that emulates the Western dietary pattern using survey data (NHANES), and we have demonstrated that this diet increases gut inflammation and colorectal cancer relative to a healthy control diet (AIN-93G), which is optimized for mouse health. However, the effect of protein source in the TWD and its effects on gut health have yet to be investigated.

Recent plant-based meat alternatives (PBM) have become increasingly popular in the market. These alternatives are created largely from soybeans, vegetable and coconut oils, colorants, and in some products, heme-iron to help mimic the nutrient profile and appearance of ground beef. Epidemiologic studies have suggested that heme-containing meats are a risk factor for colon cancer. Therefore, we designed the experiment to compare a popular heme-containing PBM to traditional dietary protein sources including red meat, dairy, and soy on gut health. Diets with differing protein sources were devised using the TWD formulation that emulates the nutrient content of a typical American diet to answer the question: For a typical American, does substituting traditional protein sources with PBM confer gut and metabolic health benefits?

To incorporate into mouse diets, we prepared ground beef and PBM by baking, freeze drying, and homogenization. We then determined the total fat content, fatty acid profile, fiber (for PBM), and the mineral content of ground beef and PBM. Experimental mouse diets were then formulated by a commercial vendor to have the same number of calories, macro and micronutrient content, and fiber. Diets only differed in protein source (beef, PBM, dairy, and soy protein). We also included a healthy control dietary treatment to compare results to our previous studies.

After two weeks on experimental diets, mice were administered a gut inflammatory agent and a carcinogen to promote colitis and carcinogenesis. Colitis severity, tumor incidence and burden, and gut inflammation were measured to determine the effect of experimental diets on gut health. Food intake and mouse body weight were measured weekly, body composition was analyzed at week 13.

Additionally, fecal samples were collected throughout the study for gut microbiome analyses. The gut microbiome is made up of trillions of non-eukaryotes that colonize primarily in the colon. These microorganisms can convey benefits or detriments to the host. Diet greatly impacts the microbiome and the microbiome in turn is involved in the etiology of several chronic diseases including colorectal cancer.

We hypothesized that dietary protein source will not affect colitis or carcinogenesis. However, we are confident the gut microbiome composition will be significantly different between mice fed different protein sources. Essentially, this research will compare the effects of ground beef, PBM, soy protein, and dairy protein on gut health and the gut microbiome.

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