Soy as an Estrogen Mimic

Here's a question from a reader:

What do you think about soy as an estrogen mimic. I'm currently in China, and there is a very common drink here called DouJiang, and it's "soymilk" boiled soybeans blended into hot water, with sugar added. I love it, and it cleared up my face. Then I did some reading in an article on Web MD, for effects of estrogen mimics (they were talking about herbal supplements) and they advised for women with a history of different cancers (breast cancer was sited) to avoid estrogen mimics. Other article, perhaps because of other good qualities of soy, say that it can prevent cancer. I was just curious about what you think.

Cuprite, my completely uneducated/uninformed answer on this subject is that... I really don't know.

Deriving what I do know from first principles... our bodies make cholesterol. Then, from cholesterol, we create the hormones known as testosterone, estrogen, progesterone... (and some other ones of other clinical significance like aldosterone and cortisol.) We call it the Steroid Synthesis Pathway and it's a very big deal for board examinations. There's only a few "real world" examples in which to apply it... and unfortunately, I've received no formal training on the subject of soy estrogens. (We're trained as human pathologists, not soy botanists.)

Plants make cholesterols too and they have what are called "phytoestrogens." These plant hormones can mimic the properties of human hormones.

Estrogen can increase the risk of thrombosis (which is why it is contraindicated to take birth control and smoke at the same time) and long term exposure can increase the risk of female cancers -- first and foremost, breast cancer. Hm. Adding to the confusion is that some synthetic hormone look-alikes have been used to treat breast cancer: Tamoxifen being the most famous.

So it is not so simple and we cannot simply say: "ooh, it looks like human estrogen so it must do stuff that it totally natural and safe and healthy!"

I performed a Pubmed search using the term: "phytoestrogen" and imposed the search limits of "Human", "Core Clinical Journal" and "English" and I found the following recent review article: Implications of phytoestrogen intake for breast cancer. CA Cancer J Clin. 2007 Sep-Oct;57(5):260-77. Their conclusions are as follows:

1) Data regarding the role of phytoestrogens in breast cancer prevention is conflicting, but suggest early exposure in childhood or early adolescence may be protective.
2) In several placebo-controlled randomized trials among breast cancer survivors, soy has not been found to decrease menopausal symptoms.
3) There is very little human data on the role of phytoestrogens in preventing breast cancer recurrence, but the few studies conducted do not support a protective role.
4) There is in vivo animal data suggesting the phytoestrogen genistein may interfere with the inhibitive effects of tamoxifen on breast cancer cell growth.

In summary, plants and animals make hormones and their interaction is complex. Eat a healthy diet, but do not take dietary supplements with the expectation that it will do something beneficial. In the US, the FDA has their hands tied for the most part but all products labeled as supplements are supposed to be safe and their claims are truthful. However, the FDA is just a regulatory agency and it is the responsibility of the manufacturers to meet this agreement since "supplements" are not held to the same standard as pharmaceuticals. There are other things beyond eating soybeans that are more likely to cause cancer. Or prevent it, as the case may be.

Thanks for your question, Cuprite! :)