Prospective Study of Antioxidant Micronutrients in the Blood and the Risk of Developing Prostate Cancer

Abstract

Antioxidant micronutrients may have chemopreventive effects. The authors examined the associations between prediagnostic blood levels of micronutrients and prostate cancer risk in two nested case-control studies of 9,804 and 10,456 male residents of Washington County, Maryland, who donated blood in 1974 (CLUE I) and 1989 (CLUE II), respectively. Until 1996, 182 men for whom adequate serum remained for assays in the CLUE I cohort and 142 men in the CLUE II cohort developed prostate cancer. Each case was matched with two controls by age, gender, race, and date of blood donation. In both cohorts, cases and controls had similar concentrations of alpha-carotene, beta-carotene, total carotene, beta-cryptoxanthin, lutein, lycopene, retinol, and ascorbic acid; serum alpha-tocopherol was weakly associated with prostate cancer risk. Higher retinyl palmitate concentrations were associated with a lower risk in CLUE I but not CLUE II. In CLUE I, cases had lower concentrations of gamma-tocopherol than did controls (p = 0.02), but no dose-response trend was observed. A strong inverse association between gamma-tocopherol and prostate cancer risk was observed in CLUE II. Findings do not replicate previous reports of a protective association between lycopene and prostate cancer, but they suggest potential chemopreventive effects of gamma-tocopherol on prostate cancer.

Serum Lycopene, Other Carotenoids, and Prostate Cancer Risk: a Nested Case-Control Study in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

“…In the Health Professionals Follow-up Study, lycopene was inversely associated with prostate cancer in two subgroups: older men (z65 years) and men without a family history of prostate cancer (29). Earlier findings of a nonsignificant inverse lycopene-prostate cancer association from the CLUE I study (23) were not confirmed on follow-up in CLUE I and CLUE II combined (24). Other prospectively designed nested casecontrol studies (25,26,47) also reported no association, whereas two retrospective case-control studies found inverse associations (27,28).…”

“…More recently, we prospectively assessed the intake of >25 tomato-related food items in almost 30,000 men in the Prostate, Lung, Colorectal, and Ovarian (PLCO) cohort (17), and found no overall association of dietary intake of tomatoes and lycopene with prostate cancer [1,338 cases, odds ratio (OR), 5th vs. 1st quintile of lycopene intake 0.95; 95% confidence intervals (95% CI), 0.79-1.13], although inverse associations were suggested for some processed tomato products commonly cooked with fat (17). Because the bioavailability of tomato-derived lycopene, an extremely lipophilic antioxidant (18), varies profoundly with heat and fat application (19)(20)(21), some studies (22)(23)(24)(25)(26)(27)(28)(29) have relied on blood concentrations as an integrated measure of lycopene intake and absorption. Overall, results from these blood-based studies are inconclusive; some of the larger studies suggest the preventive effects of lycopene in subgroups with aggressive disease (16,17,22,28), older men (29), or men without a family history of prostate cancer (29).…”

“…Initial blood-based studies (30)(31)(32) reported only on lycopene and h-carotene, whereas more recent studies (22)(23)(24)(25)(26)(27)(28)(29) also included other serum carotenoids commonly found in humans, specifically a-carotene, h-cryptoxanthin, lutein, and zeaxanthin. Results from these more detailed evaluations of carotenoids (22)(23)(24)(25)(26)(27)(28)(29) have also been inconsistent, which may be due in part to their limited sample size.…”

“…Results from these more detailed evaluations of carotenoids (22)(23)(24)(25)(26)(27)(28)(29) have also been inconsistent, which may be due in part to their limited sample size.…”

The effect of γ-tocopherol administration on α-tocopherol levels and metabolism in humans

“…Both g-tocopherol and g-CEHC inhibit cyclooxygenase and show an anti-inflammatory effect (Jiang et al, 2000;Jiang & Ames, 2003;Grammas et al, 2004). Some studies have indicated that the plasma concentration of g-tocopherol is inversely associated with the incidence of cardiovascular disease and prostate cancer (Jiang et al, 2001;Huang et al, 2003;Hensley et al, 2004). Studies by Liu have suggested that mixed tocopherols are more effective at preventing platelet aggregation and increasing nitric-oxide (NO) release, as well as activating endothelial constitutive nitric-oxide synthase (ecNOS) and increasing the superoxide dismutase (SOD) protein content in platelets (Liu et al, 2003).…”