Objective: To examine the effects of dietary isoflavone supplementation with an extract from red clover on cognitive function in postmenopausal women.
Design: Thirty postmenopausal women aged greater than 60 years received either two tablets of an extract of aglycone isoflavones from red clover (each containing formononetin 25 mg, biochanin 2.5 mg and less than 1 mg of daidzein and genistein) for 6 months in a randomized, controlled clinical trial. Cognitive function tests were performed at baseline and at the end of isoflavone or placebo therapy.
Results: Isoflavone supplementation was associated with an apparent improvement in block design (a test of visual-spatial intelligence) compared to placebo (isoflavone +12%, placebo -3%; p = 0.03), no improvement in verbal memory compared to an improvement on placebo (isoflavone +1%, placebo +29%; p = 0.023) and a deterioration in digit recall compared to placebo (isoflavone -6%, placebo +12%; p = 0.029). However, these findings were not statistically significant when corrections were made for potential chance findings due to multiple comparisons.
Conclusion: Isoflavone supplementation does not appear to have major short-term effects on cognitive function in postmenopausal women. However, further clinical trials are required to determine whether small effects or long-term effects on cognitive function occur during isoflavone supplementation.