A combined analysis of previously published studies suggests that dietary soy intake may be linked with a small reduction in breast cancer risk, but it’s still too early to recommend soy for breast cancer prevention. These results were published in the Journal of the National Cancer Institute.
Cancer prevention is an important and active area of public health research. Physicians and individuals have recognized that the best “treatment” for cancer is to prevent its occurrence in the first place. Preventive measures that have been investigated for breast cancer include diet, physical activity, and medications such as tamoxifen.
Because of the high dietary soy intake and low breast cancer risk in Asian countries, some researchers have hypothesized that soy could reduce the risk of developing breast cancer. Results from previous studies have been mixed, however, and some researchers have even suggested that soy may have estrogenic effects that could increase the risk of breast cancer.
To summarize the available information about the relationship between soy intake and breast cancer risk, researchers combined information from 18 previously published studies. The studies were published between 1978 and 2004. Combining information across studies allows researchers to evaluate large numbers of study subjects, but can be challenging because of the different approaches used in different studies.
- Results varied considerably across studies. After pooling the information, high dietary soy intake was linked with a modest 14% reduction in risk of developing breast cancer.
- There was some suggestion that the protective effect of soy may be stronger for premenopausal than for postmenopausal women.
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The researchers conclude that high dietary soy intake may be linked with a small reduction in the risk of developing breast cancer. Given the uncertainty about these findings and the inconsistencies in the evaluated studies, however, the researchers note that it would be premature to recommend dietary supplementation with soy to reduce the risk of breast cancer. The researchers also note, however, that “…there are no data to suggest that consumption of soy foods in amounts consistent with an Asian diet is detrimental to breast health, and such a diet is likely to confer benefits to other aspects of health.”
Reference: Trock BJ, Hilakivi-Clarke L, Clarke R. Meta-Analysis of Soy Intake and Breast Cancer Risk. Journal of the National Cancer Institute. 2006;98:459-71.
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