Recruiting

Cysteine Diets

Sponsor:

Purdue University

Code:

NCT07086833

Conditions

Colorectal Cancer

Eligibility Criteria

Sex: All

Age: 45 - 70+

Healthy Volunteers: Not accepted

Interventions

Low Cysteine Diet

High Cysteine Diet

Study Details

Brief summary:

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

Conditions

Colorectal Cancer

Study ID

NCT07086833

Start date

Aug 18, 2025

Status verified date

May, 2026

Completion date

Dec 1, 2027

Anticipated

Primary completion date

Dec 1, 2027

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 45 - 70+

Healthy Volunteers: Not accepted

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

Study Design

Enrollment

40 participants

Anticipated

Allocation

Randomized

Intervention Model

Crossover

Primary purpose

Prevention

Interventions and Outcome Measures

Arms

experimental: High cysteine diet

Participants will eat a diet higher in cysteine, relying on more animal based protein.

experimental: Low cysteine diet

Participants will eat a diet lower in cysteine, relying on more plant based protein.

Interventions

Low Cysteine Diet

A diet low in cysteine, about 1.4 g/1000 kcal.

High Cysteine Diet

A diet high in cysteine, about 3 g/1000 kcal.

Primary outcome measure

  • Colonic inflammation [ Time Frame: Baseline, Week 1 (Day 8), Week 2 (Day 15), Week 4 (Day 29), Week 7 (Day 49), Week 8 (Day 57), Week 9 (Day 64), Week 11 (Day 78) ]
  • Fecal microbial content [ Time Frame: Baseline, Week 1 (Day 8), Week 2 (Day 15), Week 4 (Day 29), Week 7 (Day 49), Week 8 (Day 57), Week 9 (Day 64), Week 11 (Day 78) ]
  • Systemic markers of inflammation [ Time Frame: Baseline, Week 1 (Day 9), Week 2 (Day 16), Week 3 (Day 23), Week 4 (Day 30), Week 7 (Day 50), Week 8 (Day 58), Week 9 (Day 65), Week 11 (Day 79) ]

Central Contacts and Locations

Central contacts

Patricia G Wolf, PhD, RD

765-494-1860wolfpm@purdue.edu

Locations

Purdue Clinical Research Center

Recruiting

West Lafayette, Indiana, United States, 47906

Contacts

Ariana Moffitt, MPH

765-494-1860amoffit@purdue.edu

More Information

Sponsor

Purdue University

Last update posted

May 14, 2026

Last verified

May, 2026

Keywords

  • Intestinal Neoplasms
  • Neoplasms
  • Colonic Diseases
  • Colorectal Cancer
  • Colorectal Neoplasms
  • Gut Microbiome
  • Cysteine Metabolism
  • Colorectal Adenomas
  • Intestinal Diseases
  • Cancer Prevention
  • Diet modification
  • Dietary Intervention
  • Colorectal Cancer Risk
  • Colorectal Cancer Prevention

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-10. This information was provided to ClinicalTrials.gov by Purdue University on 2026-05-14.