The health benefits associated with soya food consumption have been widely studied, with soya
isoflavones and soya
protein implicated in the protection of CVD,
osteoporosis and
cancers such as those of the breast and prostate.
Equol (7-hydroxy-3-(4'-hydroxyphenyl)-chroman), a metabolite of the soya
isoflavone daidzein, is produced via the formation of the intermediate
dihydrodaidzein, by human intestinal bacteria, with only approximately 30-40% of the adult population having the ability to perform this transformation following a soya challenge. Inter-individual variation in conversion of
daidzein to
equol has been attributed, in part, to differences in the diet and in gut microflora composition, although the specific bacteria responsible for the colonic biotransformation of
daidzein to
equol are yet to be identified.
Equol is a unique compound in that it can exert oestrogenic effects, but is also a potent antagonist of
dihydrotestosterone in vivo. Furthermore, in vitro studies suggest that
equol is more biologically active than its parent compound,
daidzein, with a higher affinity for the oestrogen receptor and a more potent
antioxidant activity. Although some observational and intervention studies suggest that the ability to produce
equol is associated with reduced risk of breast and
prostate cancer, CVD, improved bone health and reduced incidence of hot flushes, others have reported null or adverse effects. Studies to date have been limited and well-designed studies that are sufficiently powered to investigate the relationship between
equol production and disease risk are warranted before the clinical relevance of the
equol phenotype can be fully elucidated.