It is true that resveratrol is an estrogen-like molecule. We are all learning about the unusual properties of resveratrol. These unusual properties help to explain its wide margin of safety in human subjects. It is unusual in the following ways.
1. Resveratrol is the weakest of phytoestrogens, 1/7000th the action of estrogen (soy is about 1/1000th).
2. In a study using resveratrol and genistein (soy plant estrogen), they both increased vitamin D receptor protein expression (vitamin D is considered an anti-cancer vitamin). Treatment with resveratrol had no effect on cell number or cell cycle profile.
3. Resveratrol inhibits the aromatase enzyme. Aromatase inhibitors are widely prescribed to breast cancer patients. Aromatase inhibition blocks the production of estrogen.
4. In a study that compared the estrogen agonist and antagonist activity of eight plant estrogens (genistein, daidzein, equol, miroestrol, deoxymiroestrol, 8-prenylnaringenin, coumestrol and resveratrol), at varying concentrations, seven of the eight phytoestrogens (all except resveratrol) gave similar maximal responses to that given by estrogen in cell-based assays which makes them full estrogen agonists. (An agonist is amolecule that improves the activity of a different molecule.).
5. There is a great difference in the biological activity of oral administered resveratrol versus resveratrol directly administered to living cells in a lab dish. Nature delivers resveratrol to needed tissues a little bit at a time.
6. The human equivalent of 1400 mg of resveratrol has been administered to mice without toxicity. Resveratrol has passed the safety arm of three human clinical trials, two being cancer studies.