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The Effects of Soy Consumption in Correlation to Breast Cancer
Danielle Tutrone
There have been various speculations that an increased soy intake can lead to an
increased risk of breast cancer among women, or on the contrary: decrease the likelihood.
Internet search engines, blogs, and social media have become increasingly popular resources for
the public to utilize when attempting to find solutions to preventative health or medical issues.
This new phenomenon has created a widely diverse and often times, confusing market for those
wishing to seek health literacy, and in this case has the population believing that soy can either
benefit or increase the rate of breast cancer. After investigating multiple peer-reviewed articles,
results appear to be conclusive, however research is premature. Upon findings, evidence seems
to suggest that an increased soy intake decreases the chance of breast cancer, and increases the
likelihood of survival of those diagnosed. Although this is not a heavily researched topic,
appropriate studies, results, and data are in favor of soy’s potential benefits.
Another factor causing the public to be fearful of soy consumption was the professional
advice given by medical providers. Previously, ”Studies have shown that isoflavones, the major
component of soy, enhance the proliferation of breast cancer cells in vitro, promote mammary
tumor growth in rats, and possibly interfere with the effectiveness of tamoxifen.” Caan, B. J.,
Natarajan, L. et. al. (2011). Soy Food Consumption and Breast Cancer Prognosis. Cancer
Epidemiology Biomarkers Prevention, 20;854. doi:10.1158/1055-9965.EPI-10-1041 causing
physicians, especially those with patients diagnosed with breast cancer, to advise against the
consumption of soy products. In the first found controlled epidemiologic study, 3,088 breast
cancer-surviving women between the ages of 18 to 70 were investigated after and during 7 year
trial, with no previous diagnosis prior. These women were administered food questionnaires post
diagnosis, which measured levels of soy intake. Researchers measured consumption in
milligrams of isoflavones, and utilized a baseline for specific soy based items using the Arizona
Food Frequency Questionnaire. Results concluded that women who’s consumption was in the
upper percentile of the study consuming more than 16.3mg/day (the equivalent of a half a cup of
soy milk, or 2oz of tofu each day), produced data indicating a decreased likelihood of mortality.
The credibility of this study is thought to be strong with its use of a large number of individuals,
diverse population, and its use of a thorough investigation of patient demographics.
The second case controlled study examines the use of a soy containing probiotic for the
purposes of breast cancer prevention by Japanese women since adolescence. Participants were
selected in 14 various areas in japan, and were administered dietary recall questionnaires for
different stages of their life. Segments of soy intake of the studies desired life span included: age
10 to 12, 20 years old, and 10 to 15 years prior to the study, and were conducted blindly to the
case and control status. Included in data collection was patient demographics such as medical
and family history, exercise habits, education, and alcohol consumption. Ninety five percent
confidence intervals were used when calculating data indicating that there is reason to believe
that researchers did not fully support that data. Results concluded “A significant inverse
association was also seen between consumption of soy isoflavones and breast cancer
occurrence.” Toi, M., Hirota, S., Tomotaki, A., et. al. (2013). Probiotic Beverage with soy
Isoflavone Consumption for Breast Cancer Prevention: A Case-Control Study. Current Nutrition
and Food Science, 194-200. doi:10.2174/15734013113099990001. The studies strengths include
the use of nonbiased interviewees instead of relying on participants to administer their own
dietary recall, obtaining participants in various regions throughout Japan, and the thorough
investigation of known previous risk factors.
The third finding is a multi-ethnic cohort study following participant’s consumption of
soy prior to diagnosis of breast cancer. This study includes 3,842 females found in California and
Hawaii diversified in ethnicity, which included: African Americans, Native Hawaiians, Japanese
Americans, Latinos, and Caucasians. The goal of this study was to test the current hypothesis of
an inverse association between prediagnostic soy intake and breast cancer specific mortality due
to the increased use of the public as a means for alternative menopause treatment. Participants
were given a lengthy questionnaire previous to cohort, excluding women with a prediagnosis of
breast cancer and those under the age of 50. Participants self administered routine dietary recalls,
and were compared and calculated utilizing the University of Hawaii’s food composition table as
a baseline for soy composition. Results concluded that, ” The findings from this study are
consistent with previous studies that did not observe adverse effects of soy intake.” Conroy, M.
S., Maskarinec, G., Park, S. et. al. (2013). The Effects of Soy Consumption before Diagnosis on
Breast Cancer Survival: the Multiethnic Cohort Study. Nutr Cancer, 65(4), 527-537. doi:
1080/01635581.2013.776694. Data from this also suggested that a potential protective effect was
seen in participants with higher amounts of soy intake. Not only is this cohort more credible due
to its high number of participants, but also for its use of ethnic diversity.
Although there is room for improvement for all of these studies, there is enough
convincing data thus far to indicate the health benefits for soy and its use in the reduction of
breast cancer. As future studies progress, data, confidence intervals, methods, and participants
will be refined opening up avenues for more credible and concrete evidence.
References
Caan, J. B., Natarajan, L., Parker, B., Gold, B. E., Thomson, C., Newman, V., Rock, L. C., Pu,
M., Al-Delaimy, W., Pierce, P. J. (2011). Soy Food Consumption and Breast Cancer Prognosis.
Cancer Epidemiology Biomakers and Prevention, 20, 854. doi:10.1158/1055-9965.EPI-10-1041
Toi, M., Hirota, S., Tomotaki, A., Sato, N., Hozumi, Y., Anan, K., Nagashima, T., Tokuda, Y.,
Masuda, N., Ohsumi, S., Ohno, S., Takahashi, M., Hayashi, H., Yamanoto, S., Ohashi. (2013).
Prebiotic Beverage with Soy Isoflavone Consumption for Breast Cancer Prevention: A Casecontrol Study. Current Nutrition and Food Science, 9(3), 194-200.
doi:10.2174/15734013113099990001
Conroy, M. S., Maskarinec, G., Park, S., Wilkens, R. L., Henderson, E. B., Kolonel, N. L.
(2013). The effects of Soy Consumption before Diagnosis on Breast Cancer Survival: the
Multiethnic Cohort Study. Nutr Cancer 65(4), 527-537. doi: 1080/01635581.2013.776694