44 Geriatric Psychiatry C L I N I C A L P S Y C H I A T R Y N E W S • M a r ch 2 0 0 5

Soy’s Effects on Cognition, Bones DisappointingB Y K AT E J O H N S O N

Montreal Bureau

Soy supplementation was not associ-ated with significant improvementsin cognition, bone density, or lipid

profiles, compared with placebo, in morethan 200 older postmenopausal womenfollowed for 1 year, Dutch investigatorsreported.

The findings conflict with those of pre-vious studies on the subject. “Before now,

there were a few clinical trials that sug-gested some benefits of soy for bone, andat least four that suggested cognitive ben-efits, and some strong suggestion of lipidimprovements, but a lot of those trialswere both small and only about 3 monthslong,” Pauline Maki, Ph.D., of the Centerfor Cognitive Medicine at the University ofIllinois at Chicago, said in an interview.

The current study, a randomized, double-blind, placebo-controlled trial, included 202healthy women aged 60-75. But because

only older women participated in the study,Dr. Maki, who was not involved in the re-search, said she was not ready to write offthe possible benefits of soy in youngerpostmenopausal women. “There might in-deed be some benefit of soy for women ifthey start it early enough,” she noted.

Study participants were randomly as-signed to receive a daily supplement con-sisting of either 36.5 g of isoflavone-richpowdered soy protein (containing genis-tein, daidzein, and glycitein) or an equal

amount of a powdered milk protein place-bo, said Sanne Kreijkamp-Kaspers, M.D.,of University Medical Center, Utrecht,the Netherlands, and associates.

Supplementation continued for 12months. Adherence was checked by mea-suring plasma genistein levels in the finalblood sample. A total of 49 participantsdropped out of the trial, divided equallybetween the soy and placebo groups. Ofthose who remained, 90% of the womenused at least 80% of their supplementsover the course of the study ( JAMA2004;292:65-74).

At baseline, both groups performedsimilarly on cognitive function tests ofshort-term and long-term verbal and vi-sual memory, naming and verbal fluency,and complex attention. At the end of thestudy, there were no statistically signifi-cant differences in test scores betweengroups. Body mass index, history of es-trogen use, and smoking status did not af-fect these results.

Plasma lipids were also similar betweengroups at baseline. At the end of the studythe LDL and total cholesterol levels re-mained constant in the soy group, and theplacebo group experienced a small but sta-tistically insignificant decrease.

Overall, bone mineral density (BMD),measured at the hip and lumbar spine us-ing dual-energy x-ray absorptiometry(DXA), had decreased in both groups atthe end of the 12 months. One BMDmeasurement, the intertrochanter regionof the hip, was 1.3% higher in the soygroup— a significant difference— but “itwas only one comparison among 13 BMDmeasurements and may well be a chancefinding,” the investigators said.

When the results were analyzed ac-cording to the number of years since awoman’s menopause, there was a hintthat the timing of soy supplementationmay be important—at least for bone. “Inwomen who were recently menopausal,our intervention seemed to improve BMDwhile in the late menopausal women sucheffect was absent,” the authors wrote.“However, only the intertrochanter re-gion of the hip showed a statistically sig-nificant interaction” with years sincemenopause.

This subgroup of newly menopausalwomen did not experience any differenceswith soy supplementation on their lipid lev-els or cognitive function, but Dr. Makiholds out hope that earlier supplementa-tion may have a positive effect on cognition.

“The bone data show that the ‘estro-genicity’ of soy, if you will, was only ob-served in the younger women. Eventhough this study does not show a similareffect on cognition, my hope for the cog-nitive benefits for younger women comesfrom two other randomized trials thatwere composed of younger women be-tween the ages of 50 and 65, which didshow a cognitive benefit,” she said.

For their part, the researchers acknowl-edged that their 1-year study might havebeen too short to fully capture any positiveeffect of soy supplementation on bone.They also pointed out that many previousstudies in men have reported a positive ef-fect of soy supplementation on lipids. ■