title: Vegetarianism and colorectal cancer risk in a low-selenium environment: effect modification by selenium status? A possible factor contributing to the null results in British vegetarians.
abstract: BACKGROUND
  Despite the consistent findings of lower total cancer incidence in vegetarians than in meat-eaters in the UK, the results of studies of colorectal cancer (CRC) risk in British vegetarians have largely been null. This was in contrast to the hypothesis of a decreased risk of CRC in this population due to null intake of red and processed meats and increased intake of fibre. Although the data are inconsistent, it has been suggested that selenium (Se) status may influence CRC risk.
  
  
  METHODS
  A literature review was performed of studies on CRC risk in vegetarians, Se intakes and status in vegetarians, and changes of Se intakes and status in the UK throughout the follow-up periods of studies on CRC risk in British vegetarians.
  
  
  RESULTS
  Vegetarians in the UK and other low-Se areas were found to have low Se intakes and status compared to non-vegetarians. There was some evidence of a reverse J-shaped curve of Se intakes and status in the UK throughout the last three decades. These presumed patterns were followed by the changes in CRC mortality or incidence in British vegetarians during this period.
  
  
  CONCLUSIONS
  Available data on Se intake and status in British vegetarians, as well as the relationship between their secular changes in the UK and changes in CRC risk in this dietary group, are compatible with the hypothesis that low Se status may contribute to the largely null results of studies of CRC risk in vegetarians in the UK.
authors.affiliation: Cancer Epidemiology Unit, Nuffield Department of Population Health, Richard Doll Building, University of Oxford, Roosevelt Drive, Oxford, OX3 7LF, UK. jacob.sobiecki@ceu.ox.ac.uk.|Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, St Mary's Campus, London, W2 1PG, UK. jacob.sobiecki@ceu.ox.ac.uk.|Department of Paediatrics, Nutrition and Metabolic Disorders, Children's Memorial Health Institute, Al. Dzieci Polskich 20, Warsaw, 04-730, Poland. jacob.sobiecki@ceu.ox.ac.uk.
authors.forename: Jakub G
authors.initials: JG
authors.lastname: Sobiecki
mesh_terms: D015179:Colorectal Neoplasms / Q000097:blood* / Q000453:epidemiology*; D014676:Diet, Vegetarian / Q000009:adverse effects*; D004043:Dietary Fiber / Q000008:administration & dosage; D006801:Humans; D015994:Incidence; D009752:Nutritional Status; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D012643:Selenium / Q000008:administration & dosage* / Q000097:blood*; D006113:United Kingdom / Q000453:epidemiology; D000066988:Vegetarians
chemical_list: D004043:Dietary Fiber; D012643:Selenium
keywords: Colorectal cancer; Selenium; United Kingdom; Vegetarian