Nutr Cancer 2001;39(1):12-8
Dietary supplement use in the Prostate Cancer Prevention Trial:
implications for prevention trials.
Neuhouser ML, Kristal AR, Patterson RE, Goodman PJ, Thompson IM.
Cancer Prevention Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA
98109, USA. mneuhous@fhcrc.org
Nutrients included in commonly used dietary supplements, such as vitamins C and E, may
affect cancer risk. To better understand how supplement use may affect the interpretation
of cancer prevention trials, we examined dietary supplement use among participants in the
Prostate Cancer Prevention Trial, a double-blind, placebo-controlled trial of the drug
finasteride (Proscar) for the primary prevention of prostate cancer. Of 15,387 men who
completed food frequency questionnaires and dietary supplement questionnaires, 44.3% used
a multivitamin, 35% used single supplements of vitamin C or E, and 10-15% used antioxidant
mixtures or single supplements of vitamins A and D, zinc, or beta-carotene at least three
times per week. The strongest correlates of supplement use were higher education and lower
body mass index (p < 0.001), and whites and Asians were more likely to use
multivitamins and single supplements of vitamins C and E than were blacks and Hispanics.
Supplement users obtained 87% of their total daily vitamin E intake, 61-64% of vitamins A,
C, and D, and about half of beta-carotene, folate, and zinc from supplements. Because
supplements, especially antioxidants, may confer independent cancer-preventive effects,
analytic models of study findings should include exposure measurement of dietary
supplements with appropriate tests for interaction. Our results can be generalized to
similar chemoprevention trials.