Inclusion Criteria:

• Current or prior advanced adenomas. Participants with advanced adenomas are defined as participants who have polyps ≥ 1 cm, who have tubulovillous adenomas (25-75 percent villous features), who have villous adenomas (>75 percent villous), or who have severe dysplasia
• Prior curatively resected Tumor, Node, Metastasis (TNM) stage II and III colon cancer ≥ 3 years out from treatment by surgery with/without adjuvant chemotherapy; NOTE: patients with stage I (T1,2 N0) colon cancer treated by endoscopic or surgical therapy are eligible at anytime after such therapy; patients with prior stage IV disease must be ≥ 5 years status post surgical resection of all metastatic disease
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 or 1
• Ability to understand and the willingness to sign a written informed consent document
• Willingness to discontinue regular usage of calcium supplements; Exception: multi-vitamin; regular use defined as a frequency of 7 consecutive days for > 3 weeks
• Willingness to provide mandatory tissue and blood for protocol specified research; residual tissue and/or blood may be used for future research Negative pregnancy test ≤ 7 days prior to registration/randomization
• Hemoglobin (Hgb) ≥ 12.0 g/dL (women), ≥ 13.5 g/dL (men) at Mayo Clinic or within normal limits at an outside laboratory
• Platelet count ≥ 100,000/ul
• White blood cells (WBC) ≥ 3,000/ul
• Alanine aminotransferase (ALT) within institutional limits of normal
• Alkaline phosphatase within institutional upper limit of normal (ULN)
• Aspartate aminotransferase (AST) within institutional limits of normal
• Total bilirubin within institutional limits of normal
• Serum calcium ≤ institutional ULN
• Serum creatinine ≤ 1.5 x institutional ULN
• ≥ 5 rectal ACF detected by chromoendoscopy ≤ 45 days prior to registration/randomization
• Endoscopy ≤ 45 days prior to registration/randomization; Note: All adenomas or polyps will be removed according to institutional standards of care, and the cecum must visualized; this may be done at the same time as the chromoendoscopy

Exclusion Criteria:

• Any history of rectal cancer; Exception: transanal excision without radiation
• Known diagnosis of colon heritable cancer syndrome (Familial adenomatous polyposis [FAP], hereditary nonpolyposis colorectal cancer [HNPCC]) or inflammatory bowel disease (Crohn's disease, ulcerative colitis)
• Inability to swallow capsules
• Bleeding diathesis
• Any invasive malignancy ≤ 5 years prior to pre-registration;
  • Exceptions:
  • patients with nonmelanoma skin cancers that were treated with simple excisional biopsy or stage I (T1,2 N0)
  • colon cancer treated by endoscopic therapy or surgery are eligible
• History of gastroduodenal ulcers documented ≤ 1 year
• Known inability to participate in the scheduled follow-up tests
• Significant medical or psychiatric problems which would make the participant a poor protocol candidate, in the opinion of the treating physician
• Total colectomy
• Colostomy
• History of pelvic or rectal radiation therapy
• History of liver disease
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia
• Concomitant corticosteroids or anticoagulants needed on a regular or predictable intermittent basis
• Use of non-study investigational agent(s) ≤ 3 months prior to preregistration
• Chemotherapy ≤ 6 months prior to pre-registration; Note: Topical chemotherapy will be assessed on a case-by-case basis
• Any of the following:
  • Pregnant women
  • Nursing women
  • Men or women of childbearing potential who are unwilling to employ adequate contraception

    Note: This study involves an investigational agent whose genotoxic, mutagenic, and teratogenic effects on the developing fetus and newborn are unknown

• Over-the-counter green tea or green tea extract use ≤ 6 weeks prior to pre-registration; consumption of over the counter green tea extracts or drinking of green tea is not permitted during the treatment portion of this trial
• Regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) ≤ 6 weeks prior to pre-registration; regular use of NSAIDs is defined as a frequency of 7 consecutive days (1 week) for > 3 weeks; participant must abstain from regular use of NSAIDs for the duration of the study; Exception: low dose aspirin (81 mg) for those participants who are chronic users of aspirin prior to the beginning of the study
• Use of non-study investigational agents while on study