The Food Environment, Microbial Cysteine Metabolism, and Cancer Disparities

The goal of this clinical trial is to learn if changing cysteine levels in the diet can influence how the body processes cysteine in Black and White individuals aged 45-75 with a history of non-cancerous polyps. The main questions it aims to answer are: * At the beginning of the study, do Black participants have higher levels of cortisol (a stress hormone) and compounds made from cysteine in their blood when compared to White participants? * Does eating less cysteine lower the body's natural cysteine activity and lead to less gut bacteria that break down cysteine? * Does eating less cysteine lead to less inflammation in the gut and lower levels of markers of inflammation in the blood? Research will compare a high cysteine diet and a low cysteine diet, and each participant will eat both diets. Participants will be in the study for 11 weeks and 2 days. Over the course of the study, participants will: * Eat a high cysteine diet for 3 weeks, and a low cysteine diet for 3 weeks * Eat a moderate cysteine diet for 1 week before each study diet * Complete surveys * Provide blood, stool, and saliva samples * Maintain food logs