Soy Intake and Breast Cancer Risk: An Evaluation Based on a Systematic Review of Epidemiologic Evidence Among the Japanese Population

Abstract

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.

The molecular, cellular and clinical consequences of targeting the estrogen receptor following estrogen deprivation therapy

“…However, unlike the carcinogenic potential of steroidal estrogens the epidemiology literature (Chen et al , 2014, Nagata et al , 2014, Wu et al , 2008) supports the view that soy diet can reduce the risk of breast cancer. However, in western society this has been translated into the use of soy in adulthood to prevent breast cancer.…”

Breast Cancer Cell Apoptosis with Phytoestrogens Is Dependent on an Estrogen-Deprived State

“…However, the clear beneficial effects of these estrogens remain controversial. Several meta-analysis (11)(12)(13) that assessed soy exposure and breast cancer risk revealed that studies conducted in Asian countries showed a significant trend of a reduced risk with increased soy intake in both pre-and postmenopausal Asian women. On the other hand, no association was observed between soy consumption and breast cancer risk in low soy consuming Western populations (11,13), suggesting that consumption of soy products in amounts taken in the Asian population may have protective benefits.…”

Genetic Polymorphisms of Insulin-Like Growth Factor 1 and Insulin-Like Growth Factor Binding Protein 3, Xenoestrogen, Phytoestrogen, and Premenopausal Breast Cancer

“…The protective effect of dietary soy intake against bca has been demonstrated by a number of studies in Asia. A systematic review from Japan showed that soy intake is associated with a lower risk of female bca (or: 0.5-0.67) 44 . A meta-analysis from China Categorized as higher or lower than the mean of the intake by control subjects (7.84 mg/day).…”