Overview

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

Eligibility

Inclusion Criteria:

• Aged 45-75
• Up to date with CRC screening colonoscopy with a high risk of CRC, defined as a history of 3 or more adenomatous polyps (APs) or an AP >1 cm in the past 5 years
• Identify as Black or Non-Hispanic White
• If female, no menstrual period for at least six months
• Willingness to donate oral wash and stool samples
• Willingness to complete 24-hour dietary recalls

Exclusion Criteria:

• Antibiotic use within the last 6 months
• Abnormal gastrointestinal transit
• A history of organ transplantation
• Use of illicit drugs, combustible tobacco, or dietary supplements
• Pre- or probiotics within the last two months
• A history of cancer treatment within the past 12 months
• CRC or a genetic predisposition to CRC
• A baseline body weight > 450 lbs
• Weight gain or loss > 4 kg 3 months prior to study
• Significant food allergies, food preferences or therapeutic or vegetarian diets
• Menstrual cycle within the last 6 months
• Antibiotics in the last 2 months
• Cannot keep a food record for 7 consecutive days during screening after detailed instruction
• Significant medical conditions
• History of eating disorders
• Alcoholism
• Individuals under the age of 18