Soy (and phytoestrogens) are safe and helpful in breast cancer

December 9th's JAMA has an interesting study in it which is receiving a lot of press already. An analysis of over 5,000 Chinese women who survived breast cancer was conducted at Vanderbilt University. Dr. Xiao Ou Shu (and others) reviewed the women's intake of soy alone and in combination with Tamoxifen, and found significant evidence that consumption of soy at levels of about 1/4 cup of tofu daily is actually quite protective and lessens the chance of breast cancer recurring. There were over 30% fewer cases of recurrence in the women who consumed about 11 grams of soy protein daily.
This is excellent news and should serve as yet another piece of corroborating evidence that phytoestrogens are safe, useful adjuncts to both menopausal symptom treatment and cancer support, even in cases of estrogen-positive tumors.
The researchers at Vanderbilt postulated that the phytoestrogens "blocked" human estrogen from stimulating the estrogen receptor. A more sophisticated understanding includes an awareness of the two different estrogen receptor subtypes, and how phytoestrogens specifically activate the beta subtype. Estrogen-receptor beta seems to counteract the growth and division that human estrogen normally stimulates. It is very probable that phytoestrogens work at least in part by this mechanism in protecting against breast cancer.
One final note: the researchers in this current study kindly point out that soy from protein isolate or candy bars is probably not as good, and that the women in the study really ate whole-soy products like tofu and tempeh. To quote Gina Villani, director of heme/onc at the Brooklyn Medical Center:
"The take-home lesson is that whole foods are what we need to eat more of. Try to stay away from the processed stuff. Don't bulk up on soy milk or soy candy bars."
Ya think?