Soybeans contain a compound daidzein that certain bacteria living within the digestive tract of some people can metabolize, or convert, into Natural S-equol [7-hydroxy-3-(4’-hydroxyphenyl)-chroman]. Natural S-equol is not of plant origin, therefore, as it is exclusively a product of the bacterial transformation of daidzein.

Not everyone can produce Natural S-equol after soy consumption, as the production depends on the types of bacteria present in the large intestine and may be influenced by the amount of soy consumed.

About 50 percent of Asians and 20 to 30 percent of North Americans and Europeans, who in general consume less soy than Asians, have the ability to produce Natural S-equol. ^2,3,7,8

Equol production is determined via a soymilk challenge, a standard test. The challenge involves consumption of two 240 milliliter glasses of soy milk or soy food equivalent for three days followed by measures of equol concentration in urine on the test’s fourth day.⁷