Neonatal rats and immature rats exposed to coumestrol had premature estrous cycles. Flax seed oil and Soy oil are known NOT have the active phytoestrogens. Sunflower oil MAY or MAY NOT have active hormone components in it. During the fourth century B.C., Hippocrates noted that Queen Anne's Lace prevented pregnancies. The Greeks used this plant as a contraceptive.
Modern research confirms strong estrogen activity.
Fennel Used in the ancient world to prevent pregnancy and precipitate abortions. Red Clover and Yucca were found to be equal in potency to estradiol at the same concentrations. Women who harvest hops for beer begin menstruating 2 days later anecdotally. Zava has confirmed that beer has a significant amount of phytoestrogens that have moderate estrogen activity from hops used in the flavoring of beer. Bloodroot, Ocotillo, Mandrake, Oregano, Damiana, Pennyroyal, Verbenna, Nutmeg, Tumeric, Yucca, Thyme, Calamus rt., Red Clover, Goldenseal, Licorice, Mistletoe, Cumin, Fennel, Camomille, Cloves.