Relationship between plasma carotenoids and prostate cancer.

Carotenoids, particularly lycopene, are thought to decrease prostate cancer risk, but the relationship between plasma carotenoid concentrations and risk in various populations has not been well characterized. Comparing 118 non-Hispanic Caucasian men mainly from southeast Texas with nonmetastatic prostate cancer with 52 healthy men from the same area, we conducted a case-control analysis evaluating associations between risk and plasma levels of total carotenoids, beta-cryptoxanthin, alpha- and trans-beta-carotene, lutein and zeaxanthin, total lycopenes, trans-lycopene, total cis-lycopenes, and cis-lycopene isoforms 1, 2, 3, and 5. Risk for men with high plasma levels of alpha-carotene, trans-beta-carotene, beta-cryptoxanthin, and lutein and zeaxanthin was less than half that for those with lower levels. In contrast, we observed no significant associations for total lycopenes, all-trans-lycopene, and cis-lycopene isomer peaks 2, 3, and 5, although high levels of cis-lycopene isomer peak 1 were inversely associated with risk. Analysis of men with aggressive disease (Gleason scores of > or =7, n = 88) vs. less aggressive cases (Gleason scores of <7, n = 30) failed to reveal significant associations between carotenoid levels and the risk of diagnosis with aggressive disease. These findings suggest that, in these men, higher circulating levels of alpha-cryptoxanthin, alpha-carotene, trans-beta-carotene, and lutein and zeaxanthin may contribute to lower prostate cancer risk but not to disease progression.

Association between low dietary folate intake and suboptimal cellular DNA repair capacity.

Both reduced DNA repair capacity (DRC) and folate deficiency are associated with increased cancer risk. Furthermore, folate is involved in DNA repair through de novo DNA synthesis and methylation. To determine whether low dietary folate intake is associated with low cellular DRC in humans, we assessed total dietary folate intake using a food frequency questionnaire in 559 non-Hispanic white cancer-free subjects enrolled from 1995 through 2001 as controls for ongoing molecular epidemiological studies from among enrollees in a community-based multispecialty physician practice in the Houston metropolitan area. We assessed cellular DRC using the host-cell reactivation assay that measures nucleotide-excision repair capacity in peripheral blood lymphocytes. The distribution of DRC was approximately normal in this study population. In univariate analysis, subjects in the lowest tertile of total dietary folate intake (<170 microg/1000 kcal/day) exhibited a significant reduction (-18%) in DRC compared with those in the upper tertile (>225 microg/1000 kcal/day; P < 0.001). In multivariate linear regression analysis, calorie-adjusted total folate intake remained an independent predictor of DRC (P < 0.001). Additional stratification analysis indicated that this association was more pronounced in those who did not use folate supplementation (n = 230; P < 0.001) compared with those who did (n = 329; P = 0.177). Our findings suggest that low dietary folate intake is associated with suboptimal cellular DRC. Once replicated by other investigators, this finding has public health implications by reinforcing the need for folate supplementation or dietary modification for the at-risk population.

A case-control study of dietary phytoestrogens and testicular cancer risk.

A few dietary studies have found elevated testicular cancer risks for higher red meat, fat, and milk intakes and lower intakes of fruits, vegetables, and fiber. Because hormonal modulation by dietary intake of plant estrogens could affect risk of testicular cancer, we chose to explore the possible relationship between dietary phytoestrogens and testicular cancer. We conducted a hospital-based case-control study of 159 testicular cancer cases diagnosed between 1990 and 1996 and 136 adult friend-matched controls at the University of Texas M. D. Anderson Cancer Center. Amounts of phytoestrogenic compounds in foods were added to the National Cancer Institute's DietSys program and then grouped into prelignans, lignans, flavonoids, isoflavonoids, phytosterols, and coumestrol for statistical analysis, expressed per 1,000 kcal. The results of multivariate logistic regression analysis showed, after adjustment for age, education, income, ethnicity, cryptorchidism, body mass index, baldness unrelated to therapy, severe acne in adolescence, early puberty, daily fiber and fat intake, and total daily calories, no discernable monotonic increased or decreased risk estimates across quartiles of phytoestrogen intake. A U-shaped pattern was observed for lignans and coumestrol. Further evaluation of this pattern by cubic spline parameterization did fit the data, but the data were also consistent with no effect. This hypothesis-generating study does not support the premise that dietary phytoestrogens increase or decrease testicular cancer risk in young men.