The most recent findings on soy and isoflavones were presented in Washington DC on the occasion of the 9th International Symposium on the Role of Soy in Health Promotion and Chronic Disease Prevention and Treatment (October 16-19, 2010). A major part of the topics was dedicated to safety and health benefits in menopausal women, and to the issue of soy and breast cancer.
Dr. Mary Hardy (University of California, Los Angeles) presented on the clinical perspective of soy in breast cancer patients (Hardy 2010). One of the most important side aspects of breast cancer is distress and related symptoms: typical side effects of breast cancer treatment are depression (9 % of patients) and/or anxiety (19 %) (Carlson et al. 2010). Another consequence of breast cancer is a modification of the diet by the patient, as patients frequently inform themselves on disease modifying parameters in openly accessible sources such as the internet (Walsh et al. 2010). Correspondingly, breast cancer patients actively look for dietetic advice. Unfortunately, oncologists usually do not have a profound education in dietetics, and although the recommendations of the American Cancer Society state that patients should switch to a healthy diet and put an emphasis on weight management, the oncologist will usually not have specific knowledge on soy. In this situation the different points of view between patient and physician will be in disagreement, as the mostly hypothetical risks of increased soy consumption are differently viewed by the physician and by the patient. Whereas the patient is usually willing to accept a given risk when there is an expected benefit standing against it, the physician’s view is to avoid any risk regardless of the potential benefits – partly in order to avoid liability, partly as a part of the paradigms. Thus the risks are frequently overestimated by the oncologist, whereas the overall benefits are underestimated. As a consequence, known risks of medical treatments may be accepted in order to avoid the hypothetical effect of another factor for which there is insufficient education.
In the case of soy the increasing clinical evidence does not support a risk – quite in the contrary it becomes more and more evident that renouncing to soy as a measure for the prevention of a hypothetical risk goes along with renouncing to various health benefits, e.g., the effects on bones or the cardiovascular system, and the reduction of menopausal symptoms which may also be caused by chemotherapy. In addition, a dietary switch to more soy food would automatically lead to a lower caloric burden by replacement of other food items, and thus to a more effective weight management. The simple result of an improved body weight control may already positively outweigh all other potential benefits.
Not all soy effects can be attributed to the isoflavones, but the exact reason of why a dietary measure has a positive effect should be secondary to making good use of it.
Physicians should be told that 1-2 servings of soy must by now be considered safe even in ER(+) breast cancer patients. In addition, the use of soy should be strongly encouraged to young relatives of breast cancer patients as a preventive measure.
References
Hardy M (2010). Soy and the breast cancer patient: a clinical perspective. 9th International Symposium on the Role of Soy in Health Promotion and Chronic Disease Prevention and Treatment, Washington DC, 16-19 October.
Cancer 