The benefits of isoflavone depend on converting soy foods and supplements to biologically active compounds such as equol, which occurs in the intestines and is altered by age-associated conditions.

Researchers from the University of Wisconsin in Madison studied the effects of soy in older nondemented men and women.

First, the details.

  • A group of elderly men and women (62 to 89 years old) ingested 100 mg/day soy isoflavones or matching placebo tablets for 6 months.
  • Neither the participants nor the researchers knew the treatment given — double-blind.

And, the results.

  • Blood levels of genistein and daidzein (the major phytoestrogens in soy) increased significantly.
  • Blood levels of equol (an isoflavone converted from daidzein by bacteria in the intestines) didn’t.
  • While similar at the start, the groups differed over 6 months of treatment on 8 of 11 cognitive (reasoning) tests.
  • Those taking isoflavone significantly improved on tests of visual-spatial memory (the ability to mentally manipulate 2- and 3-dimensional figures) and construction, verbal fluency, and speeded dexterity.
  • But placebo-treated participants were faster in tests of executive function (carrying out, implementing, administering orders).
  • The groups had similar side-effects.

The bottom line?
In addition to being well tolerated, the authors concluded that the “data support the potential cognitive effects of soy isoflavones in older adults.”

12/14/08 21:40 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.