*Geek Box: Equol Producing Capacity
Before they can be fully absorbed, soy isoflavones are metabolised by gut bacteria; this is a step that is now recognised as a critical stage in metabolism and ultimate bioactivity of all (poly)phenolic compounds.
Due to the modifying effect of the gut microbiota, the concept of an “equol producer” has been identified, although the definition appears to be relatively arbitrary [based on levels of serum or urinary equol].
Equol-producing capacity may be a combination of genetics and the background diet; East Asian populations exhibit greater equol-production capacity compared to Western populations. Research also shows that increases in serum levels of equol may only be observed in “equol producers” compared to “equol non-producers”.
It has been suggested that equol provides more of a plausible mechanistic explanation for the association between soy foods consumption and lower risk of chronic diseases, compared to the precursor soy isoflavones. If this is the case, the distinction between “equol producers” and “nonproducers” may provide an explanation for certain of the inconsistencies in the literature.
However, as we covered in a previous Deepdive, some health outcomes that appear to benefit from soy foods may not be dependent on changes in equol levels, i.e., on equol producing capacity. Like many areas related to the interaction between dietary compounds and the microbiota, there are a lot of unknowns with this area of research and it is worth keeping an open tab on the potential modifying effect of equol producing status on the health effects of soy isoflavones.