Trial of Indole-3-Carbinol and Silibinin

Inclusion Criteria:

- Adult ≥ 18 years old

- Current smoker of ≥ 8 cigarettes per day for at least the last 6 months by self-report

- Adequate blood counts, and adequate liver and kidney function defined as follows:

- Hemoglobin ≥ 9 g/dL for women, ≥ 10 g/dL for men

- Platelet count ≥ 100 x 10^9/L

- Total bilirubin ≤ Institutional upper limit of normal (≤ 1.3 mg/dL for UMMC)

- ALT ≤ 1.5 times institutional upper limit of normal

- Creatinine ≤ 1.4 g/dL and estimated GFR ≥ 80 mL/min/1.7m2

- Able to understand the experimental nature of the study and provide informed written
consent

Exclusion Criteria:

- Chronic proton pump inhibitor, H2-blocker (i.e., ranitidine, famotidine), and/or
calcium carbonate use

- History of gastric bypass surgery, gastric banding, bowel resection, malabsorption
syndromes such as celiac sprue or pancreatic insufficiency, or other conditions that
may affect gastric or intestinal absorption of nutrients

- Current use of tobacco products other than cigarettes (i.e. snuff, snuz, smokeless
tobacco, cigars, pipes), or use of these products within 3 months of study
registration

- Major or chronic medical disease, including heart disease, poorly controlled diabetes,
etc., to be adjudicated by the principal investigator

- Known active malignancy

- History of aerodigestive malignancies

- Women who are pregnant, intend to become pregnant within 3 months of study
registration, or who are lactating. Women of childbearing potential must have a
negative urine pregnancy test within 14 days of starting the assigned intervention

- Antibiotic use within 2 months of study registration by self-report

- History of respiratory tract cancer

- Known allergy to I3C, Sil, or its components

- Psychiatric and/or social situations that would potentially limit compliance with
study requirements