Randomized study: soy no help for bones, cognition in older women; Women aged 60-75 followed for 1 year.(News)

Soy supplementation was not associated with significant improvements in cognition, bone density, or lipid profiles, compared with placebo, in more than 200 older postmenopausal women followed for 1 year. Dutch investigators reported.

The findings conflict with those of previous studies on the subject. "Before now, there were a few clinical trials that suggested some benefits of soy for bone, and at least four that suggested cognitive benefits, and some strong suggestion of lipid improvements, but a lot of those trials were both small and only about 3 months long." Pauline Maki, Ph.D., of the Center for Cognitive Medicine at the University of Illinois at Chicago, said in an interview.

The current study, a randomized, double-blind, placebo-controlled trial, included 202 healthy women aged 60-75. But because only older women participated in the study. Dr. Maki, who was not involved in the research, said she was not ready to write off the possible benefits of soy in younger postmenopausal women.

"There might indeed be some benefit of soy for women if they start it early enough," she noted.

Study participants were randomly assigned to receive a daily supplement consisting of either 36.5 g of isoflavone-rich powdered soy protein (containing genistein, daidzein, and glycitein) or an equal amount of a powdered milk protein placebo, said Dr. Sanne Kreijkamp-Kaspers of University Medical Center, Utrecht, the Netherlands, and associates.

Supplementation continued for 12 months. Adherence was checked by measuring plasma genistein levels in the final blood sample. A total of 49 participants dropped out of the trial, divided equally between the soy and placebo groups. Of those who remained, 90% of the women used at least 80% of their supplements over the course of the study (JAMA 292[1]:65-74, 2004).

At baseline both groups performed similarly on cognitive function tests of their short-term and long-term verbal and visual memory, naming and verbal fluency, and complex attention.