Phytoestrogen Consumption and Breast Cancer Risk in a Multiethnic Population (original) (raw)
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Phytoestrogens and Breast Cancer Risk
Breast Cancer Research and Treatment, 2003
Phytoestrogens are natural plant substances. The three main classes are isoflavones, coumestans, and lignans. Phytoestrogens have anticarcinogenic potential, but they have also significant estrogenic properties. For an evaluation of the effect of phytoestrogens on breast cancer risk we reviewed the analytical epidemiological data. A total of 18 studies were included . Up to now, there are 13 studies that have assessed the direct relation between the individual dietary intake of soy products and the risk of breast cancer . Overall, results do not show protective effects, with the exception maybe for women who consume phytoestrogens at adolescence or at very high doses . Only four of these 13 studies are prospective, and none of them found statistically significant breast cancer reductions. Four studies assessed urinary isoflavones excretion in relation to breast cancer . Three of these are case control studies , where excretion was measured after breast cancer occurrence and thus seriously limiting causal interpretation of the results. The only prospective study with urinary measurements before breast cancer occurrence was done in a Dutch postmenopausal population and showed a non-significant breast cancer risk reduction for high excretion . Three studies measured enterolactone (lignan): two case control studies reported a preventive effect on breast cancer risk , but the only prospective study did not . In conclusion, few prospective studies (n = 5) were done to assess the effects of phytoestrogens on breast cancer risk. None of them found protective effects. However, these prospective studies did not focus on 'age at consumption', which seems to be important based on results from dietary case control studies done so far.
Dietary phytoestrogens and breast cancer risk
The American journal of clinical nutrition, 2004
A high intake of phytoestrogens, particularly isoflavones, has been suggested to decrease breast cancer risk. Results from human studies are inconclusive. We investigated the association between phytoestrogen intake and breast cancer risk in a large prospective study in a Dutch population with a habitually low phytoestrogen intake. The study population consisted of 15 555 women aged 49-70 y who constituted a Dutch cohort of the European Prospective Investigation into Cancer and Nutriton (EPIC; 1993-1997). Data concerning habitual dietary intake in the preceding year were obtained by using a validated food-frequency questionnaire. The content of isoflavones and lignans in relevant food items was estimated through a literature search, the use of food-composition tables, and contact with experts. Newly diagnosed breast cancer cases up to 1 January 2001 were identified through linkage with the Comprehensive Cancer Center Middle Netherlands. Hazard ratios for the disease were estimated b...
Cancer Causes & Control, 2007
Objective The association between a lower incidence of breast cancer within the Asian population and the consumption of a diet high in soy has recently been the subject of much attention. To examine whether soy foods really have protective effects against breast cancer and how their influence on breast cancer is modified according to menopausal status, we conducted a population-based, prospective cohort study in Japan. Methods We analyzed the data from the Japan Collaborative Cohort (JACC) Study. From 1988 to 1990 women aged 40-79 years, completed a questionnaire on diet and other lifestyle features. Hazard ratios (HRs) were computed to examine the association between soy intake and the risk of breast cancer. Results During the mean follow-up of 7.6 years, 145 cases of breast cancer were documented. We found no significant association between the risk of breast cancer and consumption of tofu, boiled beans, and miso soup; the multivariate HRs (95% CI) in the highest category of consumption were 1.14 (0.74-1.77), 0.77 (0.47-1.27) and 1.01 (0.65-1.56), respectively. Only among postmenopausal women, we found no significant associations between soy foods and the risk of breast cancer. Conclusions This prospective study suggests that consumption of soy food has no protective effects against breast cancer. Further large-scale investigations eliciting genetic factors may clarify different roles of various soybean-ingredient foods on the risk of breast cancer.
Relationship between soy food intake and breast cancer in China
Asian Pacific Journal of Cancer Prevention Apjcp, 2011
Aims: Soy food intake may be associated with reduced risk of breast cancer, by far the most frequent cancer among women, but the results are inconsistent. We aimed to investigate the relationship further in Chinese population and to assess the importance of hormone receptor status. Methods: A case-control study was conducted with totals of 183 cases and 192 controls recruited from January 2008 to January 2011 among patients admitted to the General Hospital of PLA and the Second Affiliated Hospital of Guangzhou Medical University, China. Trained interviewers conducted face-to-face interviews using a structured questionnaire to collect information on dietary habits and potential confounding factors. Results: The highest relative to lowest soy isoflavone intake was associated with a 58% decrease risk of breast cancer (OR=0.42, 95% CI=0.22-0.80). Higher consumption of soy protein also decreased breast cancer risk, and the highest consumption reduced 54% cancer risk compared with the lowest (OR=0.46, 95%CI=0.24-0.88). The inverse association between highest intake of soy isoflavone and soy protein with the risk of breast cancer was statistically in postmenopausal women (OR=0.57, 95%CI=0.29-0.83; OR=0.50, 95%CI=0.38-0.95). In the ER/PR status stratified analysis, a significantly reduced risk was observed for ER+/PR+ breast cancer among highest intake of soy isoflavone and soy protein, with ORs of 0.47 and 0.63, respectively. Conclusion: Our study suggested that a high intake of soy food is inversely associated with breast cancer risk, the effect depending to some extent on the hormone receptor status.
Soy, Isoflavones, and Breast Cancer Risk in Japan
JNCI Journal of the National Cancer Institute, 2003
Background: Although isoflavones, such as those found in soy, have been shown to inhibit breast cancer in laboratory studies, associations between consumption of isoflavonecontaining foods and breast cancer risk have been inconsistent in epidemiologic studies. We evaluated the relationship between isoflavone consumption and breast cancer risk among women in the Japan Public Health Center-Based Prospective Study on Cancer and Cardiovascular Diseases (JPHC Study). Methods: In January 1990, 21 852 Japanese female residents (aged 40-59 years) from four public health center areas completed a self-administered questionnaire, which included items about the frequency of soy consumption. Through December 1999 and 209 354 person-years of follow-up, 179 women were diagnosed with breast cancer. Cox proportional hazards regression was used to estimate the relative risks (RRs) and 95% confidence intervals (CIs) for breast cancer in relation to consumption of miso soup, soyfoods, and estimated isoflavones. All statistical tests were two-sided. Results: Consumption of miso soup and isoflavones, but not of soyfoods, was inversely associated with the risk of breast cancer. The associations did not change substantially after adjustment for potential confounders, including reproductive history, family history, smoking, and other dietary factors. Compared with those in the lowest quartile of isoflavone intake, the adjusted RRs for breast cancer for women in the second, third, and highest quartiles were 0.76 (95% CI = 0.47 to 1.2), 0.90 (95% CI = 0.56 to 1.5), and 0.46 (95% CI = 0.25 to 0.84), respectively (P trend = .043). The inverse association was stronger in postmenopausal women (P trend = .006). Conclusion: In a population-based, prospective cohort study in Japan, frequent miso soup and isoflavone consumption was associated with a reduced risk of breast cancer. [
Japanese Journal of Clinical Oncology, 2014
Objective: We reviewed epidemiological studies of soy intake and breast cancer among Japanese women. This report is one among a series of articles by our research group, which is evaluating the existing evidence concerning the association between health-related lifestyles and cancer. Methods: Original data were obtained from MEDLINE searches using PubMed or from searches of the Ichushi database, complemented with manual searches. Evaluation of associations was based on the strength of evidence and the magnitude of association, together with biological plausibility. Results: Five cohort studies and six case-control studies were identified. Among the cohort studies, two studies observed that total soy intake (in terms of total amounts of soy foods or soy isoflavones) was associated with a moderate (0.5 relative risk 0.67 with statistical significance) or strong (relative risk 0.5 with statistical significance) risk reduction of breast cancer in postmenopausal women. Among the case-control studies, two studies reported a weak (0.67 odds ratio 1.5 with statistical significance or 0.5 odds ratio 0.67 without statistical significance) inverse association between total soy intake and the risk of breast cancer. In the former, this association was observed in all women combined-premenopausal and postmenopausal women-but in the latter, the association was confined to postmenopausal women. The associations of intakes of individual soy foods with the risk of breast cancer were generally null. There is some evidence that supports the biological plausibility of a protective effect of isoflavones on breast cancer risk. Conclusions: We conclude that soy intake possibly decreases the risk of breast cancer among Japanese women.
… Journal of Cancer …, 2005
The relationship between breast cancer and dietary phytoestrogen intake in northwestern Nigerian women was explored in a case control study involving 189 cases versus 189 matched controls. Cases had significantly earlier menarche than controls and when these were adjusted for, cases significantly consumed more dietary phytoestrogens than controls. Consumption of food items like Sorghum bicolor, Manihot esculenta and Typha domigensis appear to increase the risk of breast cancer while Oriza sativa, Mangifera indica and Musa sapientum appear protective.
Factors to consider in the association between soy isoflavone intake and breast cancer risk
Journal of Epidemiology, 2010
It has been suggested that soy isoflavones have protective effects against breast cancer. However, data from epidemiological studies are not conclusive. A recent meta-analysis showed that soy intake was inversely associated with breast cancer risk in Asian but not Western populations, which indicates that protection against breast cancer may require that women consume levels of soy typical in Asian diets. In addition to the amount of soy isoflavones consumed, the form and food source of isoflavones, timing of isoflavone exposure, estrogen receptor status of tumors, and equol-producer status and hormonal profile of individuals may modify the association between soy isoflavone intake and the risk of breast cancer. These factors might explain the heterogeneity of results from studies. This present report contrasts background data from Japanese and Western women to identify the potential modifying of these factors.
Soy intake and breast cancer risk: A meta-analysis of epidemiological studies
AIP Conference Proceedings, 2016
The impact of soy intake on breast cancer risk has been investigated extensively. However, these studies reported conflicting results. The objective of this study is to perform comprehensive review and updated meta-analysis on the association between soy intake and breast cancer risk and to identify significant factors which may contribute to the inconsistencies of results of the individual studies. Based on reviews of existing meta-analysis, we identified four main factors which contributed to the inconsistencies of results of individual studies on the association of soy intake and breast cancer risk namely; region, menopausal status of the patients, soy type and study design. Accordingly, we performed an updated meta-analysis of 57 studies grouped by the identified factors. Pooled ORs of studies carried out in Asian countries suggested that soy isoflavones consumption was inversely associated with the risk of breast cancer among both pre and postmenopausal women (OR=0.63, 95% CI: 0.54-0.74 for premenopausal women; OR=0.63, 95% CI: 0.52-0.75 for postmenopausal women). However, pooled OR of studies carried out in Western countries shows that there is no statistically significant association between soy intake and breast cancer risk (OR=0.98, 95% CI: 0.93-1.03). Our study suggests that soy food intake is associated with significantly reduced risk of breast cancer for women in Asian but not in Western countries. Further epidemiological studies need to be conducted with more comprehensive information about the dietary intake and relative exposure among the women in these two different regions.
International Journal of Cancer, 2016
Soy-food intake has previously been associated with reduced breast cancer risk. Epidemiological evidence for subgroups of breast cancer, particularly by menopausal and hormone receptor status, is less consistent. To evaluate the role of hormone receptor and menopausal status on the association between soy-food intake and breast cancer risk, we measured usual soy-food intake in adolescence and adulthood via food frequency questionnaire in 70,578 Chinese women, aged 40-70 years, recruited to the Shanghai Women's Health Study (1996-2000). After a median follow-up of 13.2 years (range:0.01-15.0), 1,034 incident breast cancer cases were identified. Using Cox models, we found that adult soy intake was inversely associated with breast cancer risk (hazard ratio-HR) for fifth versus first quintile soy protein intake=0.78; 95% confidence interval (CI):0.63-0.97). The association was predominantly seen in premenopausal women (HR=0.46; 95% CI:0.29-0.74). Analyses further stratified by hormone receptor status showed that adult soy intake was associated with significantly decreased risk of ER+/PR+ breast cancer in postmenopausal women (HR=0.72; 95% CI:0.53-0.96) and decreased risk of ER−/PR− breast cancer in premenopausal women (HR=0.46; 95% CI:0.22-0.97). The soy association did not vary by HER2 status. Furthermore, we found that high soy intake during adulthood and adolescence was associated with reduced premenopausal breast cancer risk (HR=0.53; 95% CI:0.32-0.88; comparing third versus first tertile) while high adulthood soy intake was associated with postmenopausal breast cancer only when adolescent intake was low (HR=0.63; 95% CI: 0.43-0.91). Our study suggests that hormonal status, menopausal status, and time window of exposure are important factors influencing the soy-breast cancer association.