title: Toward understanding success and failures in the use of selenium for cancer prevention.
abstract: CONCLUSIONS
  Adequate and supranutritional selenium (Se) intake, maintaining full expression of selenoproteins, has been assumed to be beneficial for human health with respect to prevention of cancer. Strikingly, the effectiveness of dietary Se supplementation depends on many factors: baseline Se status, age, gender, and genetic background of an individual; type of cancer; and time point of intervention in addition to metabolic conversion and dose of applied Se compounds.
  
  
  BACKGROUND
  Se intake levels for optimization of plasma selenoproteins in humans have been delineated. Regulation, function, and genetic variants of several selenoproteins have been characterized in the intestine, where Se-mediated prevention of colorectal cancer appears to be particularly promising.
  
  
  RESULTS
  Numerous cell culture and animal studies indicate anticarcinogenic capacity of various Se compounds but, at present, the outcome of human studies is inconsistent and, in large part, disappointing. Moreover, supranutritional Se intake may even trigger adverse health effects, possibly increasing the risk for Type 2 diabetes in Se-replete populations.
  
  
  CONCLUSIONS
  To improve protocols for the use of Se in cancer prevention, knowledge on cellular and systemic actions of Se compounds needs to be broadened and linked to individual-related determinants such as the occurrence of variants in selenoprotein genes and the Se status. Based on better mechanistic insight, populations and individuals that may benefit most from dietary Se supplementation need to be defined and studied in suitably planned intervention trials.
authors: Institute for Biochemistry and Molecular Biology I, Heinrich-Heine-University, Düsseldorf, Germany.
authors: Holger
authors: H
authors: Steinbrenner
authors: Bodo
authors: B
authors: Speckmann
authors: Helmut
authors: H
authors: Sies
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D019587:Dietary Supplements; D006801:Humans; D009369:Neoplasms / Q000517:prevention & control*; D012643:Selenium / Q000494:pharmacology*; D018036:Selenium Compounds / Q000494:pharmacology*
chemical_list: D016588:Anticarcinogenic Agents; D018036:Selenium Compounds; D012643:Selenium