What are you anyways? Well phytoestrogens aka "dietary estrogen" are molecules that have structurally similar to estrogen. This allows for them to bind to the estrogen receptor and hence produce the same response that estrogen would. You can see in the picture below that 17-b-estradiol (estrogen) has that same (cholesterol) ring structure as the phytoestrogens which allows them to have an estrogen-like effects. Now don't worry, phytoestrogens have a mild estrogenic effect... In addition, phytoestrogens can actually have an anti-estrogen effect because they can downregulate estrogen production. Once again phytoestrogens have a mild effect. However, if the exposure to dietary phytoestrogens is very high then there could be a positive or a negative consequence for human health.
Now what are the dietary sources of phytoestrogens?You probably know quite a bit about soy! Soy foods contain isoflavones (type of phytoestrogen) in the quantities of 1.2-3.3mg isoflavones per g of dry weight soy. Apparently in Asia, the average daily intake of isoflavones is 25-40mg while in America it's less than 1 mg. At least that's what the study said :P


Lastly, there's diosgenin that is derived from yams.
Interestingly, epidemiological studies found that phytoestrogens are protective aggainst postmenopausal symptoms, cardiovascular disease, bone health, breast, prostate, and colon cancers.
There was a lot of talk about soy leading to breast cancer. Now let me explain, some types of breast cancer are estrogen dependent and literally how you treat them is by blocking estrogen. So the logic was, the more estrogen then the more of that type of breast cancer. Well... not quite... The professor I interviewed last week actually found that flax seed extracts combined with current breast cancer therapy or on their own help combat cancer in mice. Cool stuff!
Furthermore, mouse models of chemical induced breast cancer have been used to show that soy proteins containing isoflavones had dose-dependent tumor formation reduction. However, this effect was lost when the mice were given soy proteins without the isoflavones.
Right now a hot topic for phytoestrogens is to use them for postmenopausal women. The current treatment during postmenopause is hormone replacement therapy (HRP), so literally going on the birth control pill. However, women find that sketchy especially some evidence showing that the birth control pill increases your chance of developing breast cancer. Therefore, using the "natural" phytoestrogens instead of the birth control pill could be a better option for postmenopausal women.
An issue with lack of menstruation and estrogen is that your bones get weaker as estrogen has a protective effect on bones. It was found that coumestrol from flax seeds can promote bone mineralization and osteoblastic differentiation (osteoblasts are bone forming cells).
A downside of phytoestrogens is that genistein (phytoestrogen metabolite) was found to promotes the process of blood coagulation, meaning that it increases thrombin formation. Thus, maybe it's not that great for those with atherosclerosis as it can lead to heart attacks and strokes.
What have you heard about soy or phytoestrogens?






