Effects of Supplemental Alpha-Tocopherol and Beta-Carotene on Colorectal Cancer: Results From a Controlled Trial (Finland)

Cancer Causes Control. 2000 Mar;11(3):197-205. doi: 10.1023/a:1008936214087.

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.

Conclusion: 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.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Colorectal Neoplasms / epidemiology*
  • Colorectal Neoplasms / mortality
  • Colorectal Neoplasms / prevention & control*
  • Dietary Supplements*
  • Double-Blind Method
  • Finland / epidemiology
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Risk Factors
  • Smoking
  • Vitamin E / administration & dosage*
  • beta Carotene / administration & dosage*

Substances

  • beta Carotene
  • Vitamin E