Soy protein with and without isoflavones fails to substantially increase postprandial antioxidant capacity.

[[abstract]]Five methods for the assessment of antioxidant capacity [whole plasma conjugated diene formation, low-density lipoprotein oxidation susceptibility, ferric-reducing ability of plasma, oxygen radical absorbance capacity and perchloric-acid-treated oxygen radical absorbance capacity (PCA-ORAC)] were used in a randomized, double blind, crossover study to determine the acute postprandial antioxidant protection imparted by the isoflavone component of soy. On separate days, 16 subjects consumed one of three isocaloric shakes containing 25g of protein in the form of soy, with 107 mg of total aglycone units of isoflavones, soy with trace isoflavones (