title: Effects of supplemental alpha-tocopherol and beta-carotene on colorectal cancer: results from a controlled trial (Finland)
abstract: BACKGROUND
  Some epidemiological investigations suggest that higher intake or biochemical status of vitamin E and beta-carotene might be associated with reduced risk of colorectal cancer.
  
  
  METHODS
  We tested the effects of alpha-tocopherol and beta-carotene supplementation on the incidence of colorectal cancer in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study, a double-blind, placebo-controlled trial among 29,133 50-69-year-old male cigarette smokers. Participants were randomly assigned to receive alpha-tocopherol (50 mg), beta-carotene (20 mg), both agents, or a placebo daily for 5-8 years. Incident colorectal cancers (n = 135) were identified through the nationwide cancer registry, and 99% were histologically confirmed. Intervention effects were evaluated using survival analysis and proportional hazards models.
  
  
  RESULTS
  Colorectal cancer incidence was somewhat lower in the alpha-tocopherol arm compared to the no alpha-tocopherol arm, but this finding was not statistically significant (relative risk (RR) = 0.78, 95% confidence interval (CI) 0.55-1.09; log-rank test p = 0.15). Beta-carotene had no effect on colorectal cancer incidence (RR = 1.05, 95% CI 0.75-1.47; log-rank test p = 0.78). There was no interaction between the two substances.
  
  
  CONCLUSIONS
  Our study found no evidence of a beneficial or harmful effect for beta-carotene in colorectal cancer in older male smokers, but does provide suggestive evidence that vitamin E supplementation may have had a modest preventive effect. The latter finding is in accord with previous research linking higher vitamin E status to reduced colorectal cancer risk.
authors.affiliation: Division of Clinical Sciences, National Cancer Institute, NIH, Bethesda, MD, 20892, USA.
authors.forename: D
authors.initials: D
authors.lastname: Albanes
authors.forename: N
authors.initials: N
authors.lastname: Malila
authors.forename: P R
authors.initials: PR
authors.lastname: Taylor
authors.forename: J K
authors.initials: JK
authors.lastname: Huttunen
authors.forename: J
authors.initials: J
authors.lastname: Virtamo
authors.forename: B K
authors.initials: BK
authors.lastname: Edwards
authors.forename: M
authors.initials: M
authors.lastname: Rautalahti
authors.forename: A M
authors.initials: AM
authors.lastname: Hartman
authors.forename: M J
authors.initials: MJ
authors.lastname: Barrett
authors.forename: P
authors.initials: P
authors.lastname: Pietinen
authors.forename: T J
authors.initials: TJ
authors.lastname: Hartman
authors.forename: P
authors.initials: P
authors.lastname: Sipponen
authors.forename: K
authors.initials: K
authors.lastname: Lewin
authors.forename: L
authors.initials: L
authors.lastname: Teerenhovi
authors.forename: P
authors.initials: P
authors.lastname: Hietanen
authors.forename: J A
authors.initials: JA
authors.lastname: Tangrea
authors.forename: M
authors.initials: M
authors.lastname: Virtanen
authors.forename: O P
authors.initials: OP
authors.lastname: Heinonen
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000517:prevention & control*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking; D014810:Vitamin E / Q000008:administration & dosage*; D019207:beta Carotene / Q000008:administration & dosage*
chemical_list: D019207:beta Carotene; D014810:Vitamin E