title: Plasma tocopherol and prevalence of colorectal adenomas in a multiethnic population.
abstract: Although vitamin E can block mutagenesis and cell transformation in vitro and can reduce the number of chemically induced colonic adenomas in mice, previous clinical trials have found no protective effect of vitamin E supplements against colorectal adenomas, and epidemiological studies have found only weak protective effects of dietary or plasma alpha-tocopherol against colorectal cancer. We previously examined first diagnosis of colorectal adenomas in a sigmoidoscopy screening population and failed to find a protective effect of dietary vitamin E. Because measurements of dietary intake may not be a good proxy of vitamin E status, we assayed plasma alpha- and gamma-tocopherol concentration for 332 subjects with colorectal adenomas and 363 control subjects from this previous sigmoidoscopy-based study. Increasing alpha-tocopherol and decreasing gamma-tocopherol levels were associated with decreased occurrence of large (> or = 1 cm) but not of small (<1 cm) adenomas; however, after adjustment for potential confounding variables, these trends were not statistically significant. A strong trend (P = 0.02) was observed by using the alpha-tocopherol:gamma-tocopherol ratio, which may be a more sensitive indicator of alpha-tocopherol intake. Subjects in the highest versus lowest quintile of alpha-tocopherol: gamma-tocopherol ratio had an odds ratio of 0.36 (95% confidence interval, 0.14-0.95) for large adenomas. The finding that a high alpha-tocopherol:gamma-tocopherol ratio is associated with decreased occurrence of large, but not of small, colorectal adenomas is consistent with previous findings that alpha-tocopherol may be protective against colon cancer. A high plasma alpha-tocopherol:gamma-tocopherol ratio may be a better predictor of decreased cancer risk than high plasma alpha-tocopherol alone.
authors.affiliation: Department of Preventive Medicine, University of Southern California/Norris Cancer Center, Los Angeles 90033, USA. ingles@hsc.usc.edu
authors.forename: S A
authors.initials: SA
authors.lastname: Ingles
authors.forename: C L
authors.initials: CL
authors.lastname: Bird
authors.forename: J M
authors.initials: JM
authors.lastname: Shikany
authors.forename: H D
authors.initials: HD
authors.lastname: Frankl
authors.forename: E R
authors.initials: ER
authors.lastname: Lee
authors.forename: R W
authors.initials: RW
authors.lastname: Haile
mesh_terms: D000236:Adenoma / Q000097:blood* / Q000453:epidemiology*; D000368:Aged; D015179:Colorectal Neoplasms / Q000097:blood* / Q000453:epidemiology*; D005006:Ethnicity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D014810:Vitamin E / Q000097:blood*
chemical_list: D014810:Vitamin E