Childhood Soy Intake and Breast Cancer Risk in Asian American Women

National Cancer Institute, Bethesda, MD, USA.
Cancer Epidemiology Biomarkers & Prevention (Impact Factor: 4.13). 05/2009; 18(4):1050-9. DOI: 10.1158/1055-9965.EPI-08-0405
Source: PubMed


Historically, breast cancer incidence has been substantially higher in the United States than in Asia. When Asian women migrate to the United States, their breast cancer risk increases over several generations and approaches that for U.S. Whites. Thus, modifiable factors, such as diet, may be responsible.
In this population-based case-control study of breast cancer among women of Chinese, Japanese, and Filipino descent, ages 20 to 55 years, and living in San Francisco-Oakland (California), Los Angeles (California) and Oahu (Hawaii), we interviewed 597 cases (70% of those eligible) and 966 controls (75%) about adolescent and adult diet and cultural practices. For subjects with mothers living in the United States (39% of participants), we interviewed mothers of 99 cases (43% of eligible) and 156 controls (40%) about the daughter's childhood exposures. Seventy-three percent of study participants were premenopausal at diagnosis.
Comparing highest with lowest tertiles, the multivariate relative risks (95% confidence interval) for childhood, adolescent, and adult soy intake were 0.40 (0.18-0.83; P(trend) = 0.03), 0.80 (0.59-1.08; P(trend) = 0.12), and 0.76 (0.56-1.02; P(trend) = 0.04), respectively. Inverse associations with childhood intake were noted in all three races, all three study sites, and women born in Asia and the United States. Adjustment for measures of westernization attenuated the associations with adolescent and adult soy intake but did not affect the inverse relationship with childhood soy intake.
Soy intake during childhood, adolescence, and adult life was associated with decreased breast cancer risk, with the strongest, most consistent effect for childhood intake. Soy may be a hormonally related, early-life exposure that influences breast cancer incidence.

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    • "Two case–control studies (Do et al., 2007;Shannon et al., 2005) along with six cohort studies (Hedelin et al., 2008;Horn-Ross et al., 2002;Keinan-Boker et al., 2004;Touillaud et al., 2006;Travis et al., 2008;Ward et al., 2008) found no association between the intake of soy products, isoflavones and breast cancer risk. In contrast, the majority of the case–control studies demonstrated an inverse association between soy food/soy products, isoflavones and breast cancer risk (Dos SantoaSilva et al., 2004;Hirose et al., 2005;Iwasaki et al., 2008Iwasaki et al., , 2009Kim et al., 2008;Korde et al., 2009;Linseisen et al., 2004;Verheus et al., 2007;Wu et al., 2002;Zhang et al., 2009a,d;Zhu et al., 2011). It is important to highlight that only two of these studies were conducted in Western populations (Linseisen et al., 2004;Verheus et al., 2007), where the mean intake of isoflavones is substantially lower than in Asian countries. "
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    ABSTRACT: Breast cancer occurs as a result between genes–diet interactions. Concerning diet, only alcohol is widely recognized for being most consistently associated with breast cancer risk. The purpose of this review is to report through a systematic way the current scientific evidence relating breast cancer and diet, through original-research studies published in English language during the last decade, assessing the consumption of specific foodstuffs/food-nutrients in relation to the disease. The available literature suggests that soy food intake seems to be inversely associated with the disease, while no association seems to be reported for dietary carbohydrates and dietary fiber intake. The consumption of dietary fat, is probably suggestive of an increase in breast cancer risk, while studies evaluating the role of fruit/vegetable, meat as well as dietary patterns and breast cancer risk, provide inconsistent results. Diet seems to be modestly associated with the disease, highlighting the need for more studies to be conducted.
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