From: Setchell, KDR. Phytoestrogens: the biochemistry, physiology, and implications for human health of soy isoflavones. Am J Clin Nutr 1998;68(suppl):1333s-46s.

To further complicate matters, soybeans are extremely versatile, and isoflavone levels differ by the form of soy consumed. Shown on this slide are isoflavone concentrations in soy products of Asian and Western origin. As you can see, evels vary dramatically.