Table 5.

Randomized, Controlled Trials of Soy or red clover for cognition in postmenopausal women

Author, year	Design	Subjects	Intervention type and duration	Outcome
Duffy, 2003 69	RCT with 2 groups: soy isoflavone supplement or placebo	Postmenopausal women not on other forms of hormone therapy Ages 50–65 n=33	Supplement contained total of 60mg isoflavones. Duration: 12 weeks	Significant improvements in recall of pictures and sustained attention tasks compared to placebo. Significantly greater improvements in learning rule reversals and a planning task
File, 2005 70	RCT with 2 groups: soy isoflavone supplement or placebo	Postmenopausal women not on other forms of hormone therapy Ages 51–66 n=50	Supplement contained total of 60mg isoflavones. Duration: 6 weeks	Significant improvements in short-term memory, frontal lobe function, mental flexibility, and planning ability in soy group compared to placebo.
Kritz-Sliverstein, 2003 71	RCT with 2 groups: isoflavone supplement or placebo	>2 years postmenopausal not using estrogen therapy Ages 55–74 n=56	Supplement contained a total of 110 mg/day of isoflavones Duration: 6 months	Significant improvement in cognitive function, for women on supplement compared to placebo.
Kreijkamp-Kaspers, 2004 34	RCT with 2 groups: ISP or casein protein	Postmenopausal women Ages 60–75 n=202	ISP contained 25.6 g/day of soy protein and 99mg/day of isoflavones. Duration: 12 months	No differences in cognitive function between the two groups
Howes, 2005 46	RCT with 2 groups: Red clover isoflavones or placebo	Postmenopausal women Age >60 n=30	Supplement contained total of 28.5mg of isoflavones, took 2 tablets a day. Duration: 6 months	No effects (after correction for multiple comparisons) of isoflavones on cognitive function.

^*Abbreviations: RCT=Randomized Controlled Trial, ISP=Isolated Soy Protein