People & Lifestyle article, April 2006
| NUTRITIONAL
ANTIOXIDANTS AND PROSTATE CANCER RISK
The Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial provides some pointers
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Vitamins E and C and ß-carotene are micronutrient antioxidants that neutralize free-radicals, which potentially contribute to prostate cancer (CaP) carcinogenesis by inducing oxidative damage to DNA and cellular components.
It is unclear whether these micronutrient antioxidants confer any protection from the risk of developing prostate cancer. This is of particular interest, as the general population is strongly interested in nutritional supplements and the SELECT trial is evaluating vitamin E and selenium for chemoprevention of cancer of the prostate.
Dr. Kirsh and associates from the National Cancer Institute, Bethesda MD and other institutions across North America evaluated the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (PLCO) database for an effect of micronutrient antioxidants and report their findings in the February 2006 issue of the Journal of the National Cancer Institute.
Participants in the PLCO trial completed a baseline 137 item food frequency questionnaire, which included questions on 12 individual supplements. Relative risks of developing CaP were correlated with intake of micronutrient antioxidants by Cox proportional hazards models.
In the 29,361 men in the trial, 1,338 cases of CaP were identified over the 8 years of follow-up. In general, there was no clear CaP risk reduction resulting from dietary or supplemental intake of vitamins E and C or ß-carotene.
However, there were subsets of participants that suggested a beneficial role for micronutrient antioxidants. In smokers, decreased risks of advanced prostate cancer were associated with increasing dose and duration of supplemental vitamin E use. In these men the age adjusted rate of advanced CaP was 492, 153 and 157 per 100,000 person-years in men who took no supplemental vitamin E, >400IU/day, and those who took vitamin E for 10 years or more, respectively.
In men with low dietary ß-carotene intake, supplemental ß-carotene at a level = 2,000ug/day correlated with decrease prostate cancer risk. Specifically, the age-adjusted risks of cancer of the prostate were 1,122 and 623 per 100,000 person-years in men who took no supplemental -carotene and at least 2,000ug/day, respectively.
These data suggest a role for specific micronutrient antioxidants in selected cohorts of men.
J Natl Cancer Inst 2006; 98:245-54