Daidzein can be converted to its end metabolite S-equol in some humans based on the presence of  certain intestinal bacteria. Based on several decades of research, S-equol has potential  for significant health benefits .Daidzein has both weak estrogenic and weak anti-estrogenic effects.  Daizein has also antioxidant activity. Foti P. et al of the Department of Food Science and Microbiology (University of Milan) compared the antioxidant activity daidzein and genistein. antioxidant activity in primary and cancer lymphocytes.

Their results showed that daidzein is just as effective as genistein in protecting cells against oxidative damage of DNA.

The antioxidant activity of daidzein was measured at concentration which could be obtained by consumption of soy products.

The anti-estrogenic effect of daidzein may explain its anti-carcinogenic, anti-atherogenic and anti-osteoporotic  activity. Epidemiological studies have long shown that people who consume a lot of soy have reduces incidences of prostate cancers.

This benefit of soy could be explained by the anti-cancer and antioxidant activity of daidzein.Constantinou AI et al (Department of Surgical Oncology, University of Illinois at Chicago) studied the effect of daidzein on the capacity of tomaxifen to prevent mammary tumours.They concluded that the combination of daidzein and tamoxifen produces increased protection against mammary carcinogenesis: tumour multiplicity was reduced by 76 percent and tumor incidence by 35 percent.

Daidzein seems to reduce the risk for osteoporosis. Studies have shown that daidzein stimulates the formation of osteoblasts, which are cells that produce bone mass.

Although the mechanism of daidzein’s anti-carcinogenic activity  is unclear,  its isoflavones  are thought  to  produce a weak estrogenic effect-the lowest of the soy isoflavones-that protects  against prostate  and breast cancer. It also stimulates osteoblasts (new bone cells) in cell cultures, suggesting that it may be able to stimulate bone formation.If you’re concerned about bone health, or protecting yourself from prostate and breast cancer, try daidzein. Available for the first time as a supplement,

it’s safer than consuming gallons of soy milk, or pounds of tofu which contain genistein, the other isoflavone that has been shown to inhibit immune function, brain function, and DNA repair.
Daidzein is the safer soy isoflavone with numerous health benefits.

There is no recommended dosage for daidzein, although the average daily intake of isoflavones in Japan is about 200 milligrams. There have been no toxic side effects associated with daidzein, but because it is a phytoestrogen, there has been some concern that it could actually stimulate the growth of estrogen-stimulated  cancers or interfere with the action of birth control pills. Men and women diagnosed with estrogen-related cancers should not consume isoflavones, as there is some research that suggests that genistein and daidzein may aggravate these conditions.

The Information had not been evaluated by the Food and Drug Administration, only for reference