Soy protein may not enhance overall cognitive ability in women

Contrary to earlier reports, a new study suggests that soy protein may not preserve overall thinking abilities in women over the age of 45, but may improve memory related to facial recognition. The study is published in the June 5, 2012, print issue of Neurology®, the medical journal of the American Academy of Neurology.

"Soy is a staple of many traditional Asian diets and has been thought possibly to improve cognition in postmenopausal women," said study author Victor W. Henderson, MD, MS, with Stanford University in Palo Alto, Calif., and a Fellow with the American Academy of Neurology. "Our study found long-term use of soy protein neither improved nor impaired overall cognition."

For the study, 313 healthy postmenopausal women between the ages of 45 and 92 were given 25 grams of soy protein daily, a dose comparable to that of traditional Asian diets, or a milk protein-matched placebo. Participants were also given tests that measured memory and other thinking abilities at the start of the study and 2.5 years later.

The study found that there was no significant change in test scores between the women who took the soy supplements and those who took the milk protein supplements. There was, however, a small improvement in visual memory, or facial recognition, in the soy protein group compared to the milk protein group by about 13 percent.

"Our study provides strong evidence that soy supplements should not be used by postmenopausal women with the main goal of enhancing overall cognitive ability," said Henderson. "On the other hand, a diet high in soy protein does not appear to have any harmful effect on thinking skills, either."