Isoflavones & Breast Cancer
Chester J. Zelasko, Ph.D. | April 2, 2002

You see them all the time--headlines screaming that "Substance X Causes This Disease" or "Substance Y May Cure That Disease." Sensational headlines may confuse consumers because they just don't know what to believe.

The science of what causes and what cures diseases is a lengthy and laborious process. What frequently happens is that we get pieces of a puzzle that will take years to complete. The challenge is to discern from this information what changes we can incorporate into our lifestyles now--changes that, while still unproven beyond all doubt, may help us and at the very least won't harm us.

One such piece of the health puzzle was a recently published study on soy isoflavones and breast cancer (1). Soy isoflavones are substances in soybeans that act like phytoestrogens, literally meaning "plant estrogens." They have a mild affinity for estrogen receptors in the body. Higher levels of estrogen have been implicated as a possible cause of breast cancer. Phytoestrogens have been the subject of much research because if the intake of soy products can reduce estrogen levels, it may reduce the risk of developing breast cancer.

That was the premise of this study. Subjects were given either a placebo or 40 mg of the soy isoflavone genistein every day for 12 weeks. The amount of the supplement reflects the amount of isoflavone typically eaten by an Asian population known for having lower rates of breast cancer. The results of the study indicated that levels of female hormones such as estrogen were lower in the women who took the supplement. They also had longer menstrual cycles. The implication is that if the cycles were longer, they would have fewer cycles over a lifetime. Thus, the reduction in exposure of breast tissue to estrogen over a lifetime would likely reduce the rate of breast cancer. There seemed to be few side effects of taking the isoflavone other than gastrointestinal problems such as gas and bloating.

This study was not perfect. About one-third of the subjects dropped out, mostly because they couldn't remember to take the supplements. It was short, lasting only 3 months. However, the side effects were few and only occurred in a few women, and the potential for benefit is good. Therefore, when combined with all the other studies on isoflavones, it's reasonable to suggest that women consider eating more soy products such as tofu, texturized soy protein, and/or take a supplement that contains isoflavones to promote breast health.

Health is not found in popping pills but in a consistent, persistent effort to learn healthier habits that include: eating lots of fruits and vegetables; lowering fat intake, especially saturated fats; maintaining a normal body weight; and getting some exercise every day. Adding more isoflavone-containing soy products is a reasonable addition to those health habits.


  1. Kumar N, et al. The Specific Role of Isoflavones on Estrogen Metabolism in Premenopausal Women. Cancer 2002. 94:1166-1174.
BBBOnLine Reliability Seal © 2011 Better Life Unlimited™
A division of Better Life Institute © (BLI, Inc.)
 Contact Us  |  Privacy Policy
SecurityMetrics Credit Card Safe