This randomized phase I trial is studying the side effects and best dose of diindolylmethane in healthy volunteers. Chemoprevention is the use of certain drugs or substances to keep cancer from forming, growing, or coming back. The use of diindolylmethane may keep cancer from forming. Collecting and storing samples of blood and urine from healthy volunteers to study in the laboratory may help doctors learn more about the way a person's body handles the drug.