Regression analysis showed that doubling isoflavone intake increased plasma concentrations by 55-62 % ( s.e. 1-2 % , R ( 2 ) > 0.87 ) for daidzein , genistein , equol ( only for producers ) and total isoflavones ; for glycitein the association was weaker ( 151 % , R ( 2 ) = 0.48 ) .