Daidzein
Daidzein is one of several known isoflavones. Isoflavones compounds are found in a number of plants, but soybeans and soy products like tofu and textured vegetable protein are the primary food source. Up until recently, daidzein was considered to be one of the most important and most studied isoflavones, however more recently attention has shifted to isoflavone metabolites. Equol represents the main active product of daidzein metabolism, produced via specific microflora in the gut. The clinical effectiveness of soy isoflavones may be a function of the ability to biotransform soy isoflavones to the more potent estrogenic metabolite, equol, which may enhance the actions of soy isoflavones, owing to its greater affinity for estrogen receptors, unique antiandrogenic properties, and superior antioxidant activity. However, not all individuals consuming daidzein produce equol. Only approximately one-third to one-half of the population is able to metabolize daidzein to equol. This high variability in equol production is presumably attributable to interindividual differences in the composition of the intestinal microflora, which may play an important role in the mechanisms of action of isoflavones. But, the specific bacterial species in the colon involved in the production of equol are yet to be discovered.  (A3191, A3189).