- Soy proteins could interact with genes linked to breast cancer growth, particularly in women already diagnosed with the disease, but this should not deter women from consuming soy products such as tofu moderately. Soy supplements, however, are advised against for these women.
- Although women in countries with high soy intake show lower incidences of breast cancer, soy’s phytoestrogens might stimulate breast tumor proliferation. These plant compounds present weak estrogen-like characteristics.
- In a study involving 140 women diagnosed with early-stage breast cancer, about 20% of the women consuming soy protein supplements showed increased blood concentrations of genistein, a soy phytoestrogen. Some of these women also showed increased activity in some genes known to promote tumor growth.
- Despite the observation of increased gene activity related to tumor proliferation in some study participants, no ‘tumor proliferation’ evidence was found, possibly due to the brevity of the study period.
- Further research is needed to understand the potential effects of soy consumption later in life on breast cancer, with some experts suggesting the timing of estrogen and soy phytoestrogen administration could be crucial.
Studies suggest an intriguing interplay between soy protein and the genes linked to breast cancer growth, specifically in women who are already diagnosed with the disease. However, these findings, as published in the Journal of the National Cancer Institute, should not deter women from continuing to enjoy their tofu servings.
For safety measures, the authors advocate that women with breast cancer consume soy products moderately and refrain from supplements. As for women who haven’t been diagnosed with breast cancer, the study stops short of providing any insights into whether soy could heighten the risk.
The Soy-Breast Cancer Nexus
Dr. Jacqueline Bromberg, a breast cancer specialist from the Memorial Sloan Kettering Cancer Center, acknowledges the complex relationship between soy and breast cancer. On one end of the spectrum, women from nations where soy constitutes a major part of the diet such as Japan, display lower rates of acquiring breast cancer. On the other hand, soy comprises phytoestrogens, plant components possessing weak estrogen-like characteristics. Laboratory investigations show these soy compounds may stimulate the proliferation of breast tumors.
Inside the Study
In Bromberg’s study, 140 women freshly diagnosed with an early-stage of breast cancer were divided randomly into two clusters. One group was put on a routine soy protein supplement for a duration between one to four weeks, while the other consumed milk powder for comparison. The subjects were either premenopausal or had just crossed menopause.
Equivalent to about four cups of soy milk daily, the soy supplement, a powder mixed with water or juice, was typically consumed for two weeks. Within this brief experience, an estimated 20 percent of the soy-consuming women showed elevated blood concentrations of genistein, a soy phytoestrogen. Moreover, heightened activity in certain genes known to promote breast tumor growth and spread was observed in some of these women.
Bromberg emphasizes the uncertainty of these findings, questioning if this necessarily implicates a more rapid tumor growth or not. Despite the upregulated gene activity in these women, no evidence of ‘tumor proliferation’ was found, although the brevity of the study may affect such a discovery.
In her words, consuming soy supplements for two weeks was sufficient to amplify the expression of genes linked to tumor proliferation. For adequate safety, she advises women diagnosed with breast cancer to refrain from soy supplements and consume soy foods, like tofu and tempeh, sparingly.
Unaffiliated with the study, other breast cancer researchers concur with Bromberg’s advisement to avoid soy supplements, notably within a few years post-menopause. Yet an unanswered query remains – can the use of soy later in life pose beneficial against breast cancer? This question emerged on Craig Jordan, the scientific director of the Lombardi Comprehensive Cancer Center at Georgetown University’s radar.
He proffers that laboratory studies and human investigations demonstrate that “timing is everything” when it comes to estrogen replacement. For instance, he features a reference to the Women’s Health Initiative, a comprehensive U.S. research exploring the effects of hormone replacement therapy. As reported in this study, women receiving estrogen alone (sans progesterone) demonstrated a diminisher risk of breast cancer compared to those on a placebo.
In fact, Jordan raises the possibility that the timing of estrogen – and potentially soy phytoestrogens – administration could contribute to the reduction or growth of breast cancer cells. Thus, far from menopause, soy might be beneficial. However, this assumption awaits a clinical validation.
For more knowledge regarding soy and its potential cancer risk, the American Cancer Society is a good resource.