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Proposes a set of questions to evaluate the efficacy of a particular food for disease prevention. Use of the proposed questions in the evaluation of the claim that flaxseed may reduce the risk of breast cancer; List of proposed questions; Purposes of the questions; Circumstantial evidence; Mechanistic rationale for chemoprevention; Evidence for risk reduction; Risks associated with flaxseed consumption.

Selenium deficiency has been associated with cancer risk in several organs. This association was investigated in neoplasia of the colorectum.A case-control study is reported with two patient series, colorectal cancer and colorectal adenomatous polyps, and a control group found to be free of colorectal neoplasia. Diagnosis was determined by colonoscopy and histologic review of suspected neoplasms. Serum drawn at the time of colonoscopy was subsequently assayed for selenium content, and quartiles based on selenium were defined. Crude and adjusted odds ratios with 95 percent confidence intervals for adenoma related to selenium were calculated, controlling for known or suspected risk factors including gender, age, race, body mass index, family history, tobacco use, alcohol consumption, serum beta carotene, serum alpha tocopherol, and serum ferritin.There were 138 controls who had no neoplastic disease, 139 adenoma patients, and 25 cancer patients. For adenoma, comparing higher quartiles of selenium to the first (lowest selenium), the adjusted odds ratio for the second quartile was 1.7 (95 percent confidence interval, 0.8-3.7), the third quartile was 1.4 (0.7-3.2), and the fourth (highest selenium) quartile was 1.8 (0.9-4). The odds ratios for cancer patients were 0.8 for the second quartile, 1 for the third quartile, and 1.7 for the fourth quartile.No trend could be detected toward a protective effect of higher levels of serum selenium for colonic benign or malignant tumors. [ABSTRACT FROM AUTHOR]