This study examines the effects of a dietary supplement of isoflavones on cognitive function in postmenopausal women.
Participants for this 6-month, double-blind, randomized, placebo-controlled clinical trial were women who were in good health, were postmenopausal at least 2 years, and were not using estrogen replacement therapy. Between July 24, 2000, and October 31, 2000, 56 women aged 55 to 74 years were randomized; 2 in the placebo group and 1 in the active treatment group did not complete the 6-month evaluation, and none withdrew because of adverse effects. Women randomized to active treatment (n = 27) took two pills per day, each containing 55 mg of soy-extracted isoflavones (110 mg total isoflavones per day; Healthy Woman: Soy Menopause Supplement, Personal Products Company, McNeil-PPC Inc., Skillman, NJ, USA). Women assigned to placebo (n = 26) took two identical-appearing pills per day containing inert ingredients. Cognitive function tests administered at baseline and follow-up included the following: Trails A and B, category fluency, and logical memory and recall (a paragraph recall test assessing immediate and delayed verbal memory).
At baseline, all women were cognitively intact; there were no significant differences by treatment assignment in age, education, depressed mood, or cognitive function (all P values > 0.10). Compliance was 98% and 97%, respectively, in the placebo and treatment groups; all women took at least 85% of their pills. The women in the treatment group did consistently better, both as compared with their own baseline scores and as compared with the placebo group responses at 6 months. Comparisons of percentage change in cognitive function between baseline and follow-up showed greater improvement in category fluency for women on active treatment as compared with the case of those on placebo (P = 0.02) and showed (nonsignificantly) greater improvement on the two other tests of verbal memory and Trails B.
These results suggest that isoflavone supplementation has a favorable effect on cognitive function, particularly verbal memory, in postmenopausal women.
From the University of California, San Diego, School of Medicine, Department of Family and Preventive Medicine, Division of Epidemiology, La Jolla, CA.
Received July 1, 2002; revised and accepted October 16, 2002.
This work was supported by an unrestricted gift from Johnson & Johnson and National Institutes of Health grant M01 RR00827.
Address reprint requests to Donna Kritz-Silverstein, PhD, Department of Family and Preventive Medicine, 0631-C, 9500 Gilman Drive, La Jolla, CA 92093-0631, USA. E-mail: email@example.com.