Objective: This study examines the effects of a dietary supplement of isoflavones on cognitive function in postmenopausal women.
Design: 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).
Results: 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.
Conclusion: These results suggest that isoflavone supplementation has a favorable effect on cognitive function, particularly verbal memory, in postmenopausal women.