Date of Award:

5-2026

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Nutrition, Dietetics, and Food Sciences

Committee Chair(s)

Stephan van Vliet

Committee

Stephan van Vliet

Committee

Korry Hintze

Committee

Sulaiman K. Matarneh

Committee

Taylor Oberg

Committee

Kara J. Thornton-Kurth

Abstract

There is a popular saying: “You are what you eat.” But does this also mean, “You are what your food eats”? This dissertation explores that question by examining how farming practices shape the nutritional quality of meat—and what, if anything, those differences mean for the people who consume it. While modern livestock production and nutrition research often emphasize protein and fat, this work tests the idea that animals function as biological mediators, linking soil and plant conditions to human diets through the chemical composition of meat and milk. To evaluate this hypothesis, we tracked health-relevant plant compounds— phytonutrients—across the soil–plant–animal–human continuum through five complementary studies. 

First, a comprehensive review of scientific literature found that ruminants (such as cows and goats) do not simply accumulate plant compounds; they can bio-transform plant material into distinct antioxidants detectable in meat and milk, supporting the view that animal foods participate in a broader phytochemical ecology. Next, we analyzed beef produced under grass-fed and grain-based finishing systems, spanning local research sites and a large North American survey of more than 100 operations. Across these datasets, production system was associated with consistent nutritional differences: grass-fed beef contained higher concentrations of antioxidant-related compounds, including vitamin E, β-carotene, and multiple plant-derived phenolics, whereas grain-fed beef tended to be higher in several B-vitamins. These results indicate that what cattle eat leaves measurable “metabolic fingerprints” in the food they produce. 

To place these findings in an evolutionary context, we compared domesticated livestock products to a reference benchmark—wild game species such as elk, deer, and nilgai. Because wild herbivores forage from highly diverse plant communities, their tissues exhibited substantially greater phytochemical richness (ranging from 260 to 1030%-fold higher concentrations) and more unique metabolite profiles than feedlot-finished meat, highlighting the extent to which dietary simplification in production systems can dilute bioactive food compounds. 

Finally, we asked whether food-level differences translate into measurable changes in humans. In a controlled randomized crossover trial, participants consumed diets sourced from either regenerative or conventional agricultural systems for six weeks. Regenerative foods generally contained higher concentrations across multiple phytonutrient classes, but the human response was selective: plant-derived markers increased, whereas other compounds (including carotenoids) appeared more tightly regulated and did not shift rapidly over the study period. Importantly, a whole-food dietary pattern improved several health-related markers regardless of production system, underscoring that overall diet quality remains a major driver of health outcomes. 

Together, these studies demonstrate that agricultural management can meaningfully reshape the bioactive chemistry of animal foods. Meat from diverse, pasture-based systems may offer a nutritional “bonus” in specific compounds, but the translation to human biology is nuanced—suggesting that improving both agricultural practices and overall dietary patterns will be most important for advancing public health.

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Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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