Question asked by Curious, Texas
One of my neighbors has breast cancer. Her doctor has asked her to completely stop eating soy and its products, including edamame and tofu. My neighbor used to eat tofu at least three times a week before she got breast cancer. Is there a link between soy and breast cancer? Is there a potential that I will get breast cancer because I used to eat edamame?
Your neighbor's doctor is concerned about estrogenic stimulation, which can cause breast cancer. Some of the most effective breast cancer treatments involve blocking estrogen stimulation. Soy does have estrogens, but I believe a moderate amount of soy in the diet is still a good idea for most people.
Within the normal diet there are a number of naturally occurring plant-derived compounds called phytoestrogens. Even green beans, peanuts and dates have some phytoestrogen content, but flaxseed, soy and soy byproducts are especially high in phytoestrogens. These compounds are called phytoestrogens as a group, but you may be more familiar with them when they are also referred to by their categories within the phytoestrogen family - the flavonoids, isoflavones, coumestans or lignans.
The phytoestrogens have some pro-estrogenic activity and some anti-estrogenic activity. The concern is that estrogenic stimulation can in some circumstances promote breast cancer development. Within the past few years, we have come to realize that some post-menopausal estrogen replacement therapies increased risk of breast cancer, and as a result more attention is being paid to all forms of estrogen stimulation.