Soy and its constituents have been shown in many in vivo and in vitro studies and in some epidemiological studies to have anti-cancer effects. Some soy constituents, however, also stimulate cell proliferation, which has raised concerns in promoting soy intake among breast cancer survivors. To investigate whether soy intake may be associated with breast cancer survival, we evaluated data from a cohort of 1459 breast cancer patients who participated in the Shanghai Breast Cancer Study between 1996 and 1998. Usual soy food intake was assessed using a validated food frequency questionnaire at baseline. The median follow-up time for this cohort of women was 5.2 years. We found that soy intake prior to cancer diagnosis was unrelated to disease-free breast cancer survival (adjusted hazard ratio [HR]=0.99, 95% confidence interval [CI], 0.73-1.33 for the highest tertile compared to the lowest tertile). The association between soy protein intake and breast cancer survival did not differ according to ER/PR status, tumor stage, age at diagnosis, body mass index (BMI), waist to hip ratio (WHR), or menopausal status. Additionally, the soy-survival association did not appear to vary according to XbaI or PvuII polymorphisms in ER-alpha, or C(14206)T, G(25652)A, or A(50766)G polymorphisms in ER-beta. These data suggest that soyfoods do not have an adverse effect on breast cancer survival.
These data suggest that breast cancer risk associated with measures of body size may be mediated, at least partially, by levels of endogenous sex hormones.
These data are consistent with hypotheses and previous findings that higher folate intake may reduce risk for colorectal neoplasms, perhaps especially among those who consume more alcohol.
Limited epidemiological evidence suggests that calcium intake may be related to breast cancer risk. Data from a large, population-based, case-control study (n = 1,459 cases, 1,556 controls) conducted in Shanghai, China, between 1996 and 1998 were used to investigate the association between calcium intake and risk for breast cancer. Diet was assessed using a quantitative food-frequency questionnaire. The multivariate-adjusted odds ratio (OR) comparing all women combined in the highest to lowest deciles of total calcium intake was 0.74 (95% confidence interval [CI] = 0.46-1.20). Whereas calcium primarily derived from poultry was inversely associated with risk for breast cancer (comparing the highest to lowest quintile OR = 0.71, 95% CI = 0.55-0.93) with a statistically significant test for trend, calcium derived from milk, seafood, fruit, and vegetables was not associated with risk of breast cancer. Given that breast cancer is one of the top contributors to cancer incidence worldwide, even a moderate inverse association between calcium and breast cancer risk, if confirmed, could have important public health implications in breast cancer prevention.
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