Research on the relation between phytoestrogens and breast cancer risk has been limited in scope. Most epidemiologic studies have involved Asian women and have examined the effects of traditional soy foods (e.g., tofu), soy protein, or urinary excretion of phytoestrogens. The present study extends this research by examining the effects of a spectrum of phytoestrogenic compounds on breast cancer risk in non-Asian US women. African-American, Latina, and White women aged 35-79 years, who were diagnosed with breast cancer between 1995 and 1998, were compared with women selected from the general population via random digit dialing. Interviews were conducted with 1,326 cases and 1,657 controls. Usual intake of specific phytoestrogenic compounds was assessed via a food frequency questionnaire and a newly developed nutrient database. Phytoestrogen intake was not associated with breast cancer risk (odds ratio = 1.0, 95% confidence interval: 0.80, 1.3 for the highest vs. lowest quartile). Results were similar for pre- and postmenopausal women, for women in each ethnic group, and for all seven phytoestrogenic compounds studied. Phytoestrogens appear to have little effect on breast cancer risk at the levels commonly consumed by non-Asian US women: an average intake equivalent to less than one serving of tofu per week.

Background: Migrant studies have shown that breast cancer risk increases in women who move from countries with low incidence rates to countries with high rates. We examined the influence of migration history and acculturation on breast cancer risk in Hispanic women ages 35 to 79 years. Methods: In a population-based case-control study conducted in the San Francisco Bay Area, information on migration history, language usage, and other risk factors for breast cancer was collected through an in-person interview for 991 cases and 1,285 controls. Results: Breast cancer risk was 50% lower in foreign-born Hispanics than U.S.-born Hispanics. Risk increased with increasing duration of residence in the United States, decreasing age at migration, and increasing acculturation. Among long-term foreign-born residents, risk was lower among Hispanics who moved to the United States at age z20

Substantial experimental evidence indicates that the hormonal form of vitamin D promotes the differentiation and inhibits the proliferation, invasiveness, and metastasis of human prostatic cancer cells. Results from epidemiologic studies of vitamin D status and/or vitamin D receptor (VDR) polymorphisms and prostate cancer risk have been mixed. We conducted a population-based, case-control study of advanced prostate cancer among men ages 40 to 79 years from the San Francisco Bay area. Interview data on lifetime sun exposure and other risk factors were collected for 905 non-Hispanic White men (450 cases and 455 controls). Using a reflectometer, we measured constitutive skin pigmentation on the upper underarm (a sun-protected site) and facultative pigmentation on the forehead (a sun-exposed site) and calculated a sun exposure index from these measurements. Biospecimens were collected for 426 cases and 440 controls. Genotyping was done for VDR polymorphisms in the 5V regulatory region (Cdx-2), exon 2 (FokI), and the 3V region (TaqI and BglI). Reduced risk of advanced prostate cancer was associated with high sun exposure determined by reflectometry [odds ratio (OR), 0.51; 95% confidence interval (95% CI), 0.33-0.80] and high occupational outdoor activity (OR, 0.73; 95% CI, 0.48-1.11). Significant risk reductions with the high-activity alleles FokI FF or Ff, TaqI tt, and BglI BB genotypes and a nonsignificant reduction with Cdx-2 AG or AA genotype were observed in the presence of high sun exposure, with ORs ranging from 0.46 to 0.67. Our findings support the hypothesis that sun exposure and VDR polymorphisms together play important roles in the etiology of prostate cancer. (Cancer Res 2005; 65(12): 5470-9)

Considerable evidence indicates that vitamin D may reduce the risk of several cancers, including breast cancer. This study examined associations of breast cancer with sun exposure, the principal source of vitamin D, and vitamin D receptor gene (VDR) polymorphisms (FokI, TaqI, BglI) in a population-based case-control study of Hispanic, African-American, and non-Hispanic White women aged 35-79 years from the San Francisco Bay Area of California (1995-2003). In-person interviews were obtained for 1,788 newly diagnosed cases and 2,129 controls. Skin pigmentation measurements were taken on the upper underarm (a sun-protected site that measures constitutive pigmentation) and on the forehead (a sun-exposed site) using reflectometry. Biospecimens were collected for a subset of the study population (814 cases, 910 controls). A high sun exposure index based on reflectometry was associated with reduced risk of advanced breast cancer among women with light constitutive skin pigmentation (odds ratio = 0.53, 95% confidence interval: 0.31, 0.91). The association did not vary with VDR genotype. No associations were found for women with medium or dark pigmentation. Localized breast cancer was not associated with sun exposure or VDR genotype. This study supports the hypothesis that sunlight exposure reduces risk of advanced breast cancer among women with light skin pigmentation.