Phase I Study of Indole-3-Carbinol and Silibinin

What is the purpose of the study?

The American Lung Association estimates that there are nearly 225,000 new cases of lung cancer a year in the United States, and nearly 2 million internationally. These cases are often diagnosed too late for a cure and 5-year survival rates are low.

This study furthers the work of “preclinical” research that tested the dietary supplements Indole-3-Carbinol” (I3C), a chemical found in vegetables such as broccoli and Brussels sprouts, and Silibinin (Sil), a chemical found in the seeds of the milk thistle plant. Preclinical means that the research was conducted in the lab and using animals. Preclinical studies are required before testing in humans can be started. Both I3C and Sil can help prevent lung tumors caused by cancer-causing chemicals in tobacco from forming in animals, and combining the two was more effective than each one individually. We would like to eventually see if the same result is seen in people.

These supplements have been individually studied in people already. However, this study is the first step in human research combining the two supplements, and it is only enrolling healthy volunteers who smoke cigarettes rather than persons with a particular disease or condition.

Both I3C and Sil are available in the vitamin/supplement section of grocery stores and through the mail; however, they are not usually taken together. The goal of this research is to learn more about I3C and Sil when taken together, including side effects, as well as, how it is taken up and broken down by the body. The ultimate long-term goal is to confirm pre-clinical findings that I3C and Sil may prevent smokers from developing tobacco-related lung cancer.

How often are the clinic visits? 

This study requires at least 4 study related visits to the study center over a 8 week period, including two timed blood draws over 6 hours.

What will I be doing in the study? 

If you are eligible and agree to take part in the study, you will be asked to take either I3C or Sil alone or a combination of the two supplements, as assigned to you at study enrollment, twice a day by mouth for 8 weeks. During this period you need to complete a daily log to record your taking the study agent(s) and side effects, if any, you are experiencing. You also will record the number of cigarettes you smoke and complete a food diary on a daily basis. At certain visits we will collect cells from the inside of your mouth, cheek or nose, blood and/or urine.

Will I be compensated? 

Yes, you will be compensated up to $600 for your time and effort and for completing all study related procedures. 

What should I do if I'm interested?

If you would like to find out if you qualify for this study please contact us at 612-624-5286 or and leave your name and a contact number in your voicemail or email.

We are looking for...

Men and Women ages 18 years or older who are in generally good health. 

Study Coordinator

If you would like to find out if you qualify for this study please call
612-624-5286 or email


Tobacco Research Programs
717 Delaware St SE
Minneapolis, MN 55414

Phone: 612-626-5155
Fax: 612-624-4610