Soy Isoflavones Don't Improve Cognition in Those With Alzheimer's Disease
Madison, Wisconsin - Consuming soy isoflavones did not improve cognition in people with Alzheimer’s disease, despite an earlier study showing that a supplement form of these plant estrogens did improve memory in healthy older adults.
In a report published online by the Journal of Alzheimer’s Disease, Dr. Carey Gleason and colleagues reported the results of a placebo-controlled study in 59 people with Alzheimer’s disease. Participants received either a placebo or 100 milligrams per day of an isoflavone supplement, which is derived from soybeans. While people who received the supplement showed increases in their blood plasma levels of the isoflavone metabolites, they did not show improvements on cognition tests.
“For older adults with Alzheimer’s dementia, taking a soy isoflavone supplement did not appear to alter cognition,” says Gleason, associate professor of medicine at the University of Wisconsin School of Medicine and Public Health. Gleason does her research at the Geriatric Research, Education and Clinical Center (GRECC) at the William S. Middleton Memorial Veterans Hospital.
Soy isoflavones contain daidzein, which intestinal bacteria can convert to S-equol, a molecule highly similar to estrogen. However, only about 30 percent of Americans can convert daidzein to S-equol. While there are conflicting reports, some studies suggest that S-equol may be the most potent of the plant estrogens with the greatest health-related effects.
Gleason says the present study revealed associations between S-equol levels and improvements in speeded dexterity and verbal fluency. Additionally, the study showed wide differences in how individuals metabolize the soy isoflavones.
“It is possible that only those individuals whose gut micro-flora are able to produce S-equol will benefit cognitively from isoflavone therapies,” Gleason adds, “so more study is needed on differences in metabolism and unique effects of the isoflavone metabolites.”
The study is being published in the September edition of the Journal of Alzheimer’s Disease.
This research was supported by funding from the NIH (K23 AG024302; P50 AG033514).
Date Published: 08/24/2015