Table 2.

Studies of soy/isoflavones

Menopausal symptoms
Reference	Study Design	# of Participants	Dosage/form	Duration	Results
Albertazzi et al, 1998 52	Multicenter RCT: placebo vs. soy protein	104 postmenopausal women	Soy protein isolate: 60 g daily	12 weeks	Significant 15% reduction in hot flashes for soy group compared to placebo
Washburn et al, 1999 53	RCT, crossover trial: placebo vs. soy protein	51 women with vasomotor symptoms	Soy protein: 20 g with 34 mg phytoestrogens	6 weeks	Significant reduction in severity of vasomotor symptoms compared to carbohydrate placebo.
Upmalis et al, 2000 54	Multicenter RCT: placebo vs. isoflavone extract	177 postmenopausal women with hot flashes	Soy isoflavone extract: 50 mg	12 weeks	Marginally significant (p=.08) reduction in hot flashes.
Faure et al, 2000 55	Multicenter RCT: placebo vs. isoflavone extract	75 postmenopausal patients with hot flashes	Soy isoflavone extract: 70 mg genistein and diadzein	16 weeks	Significantly reduced hot flashes 40% more than placebo over the course of the trial.
Crisafulli et al, 2004 56	RCT with 3 groups: (1) isoflavone, (2) estrogen/progestin therapy (3) placebo	90 postmenopausal women	Genistein: 54 mg/day	1 year	Genistein significantly reduced hot flashes by 24% after 1 year compared to placebo. Estrogen/progestin therapy significantly reduced hot flashes compared to placebo and genistein.
Van Patten et al, 2002 57	RCT: stratified by tamoxifen use Soy vs. placebo beverages	123 postmenopausal women with hot flashes previously treated for breast cancer	Soy beverage with 90 mg isoflavones, Placebo: rice beverage	12 weeks	No significant difference in number or severity of hot flashes between rice beverage and soy beverage groups.
Secreto et al, 2004 58	RCT with 4 groups: (1) soy isoflavones (2) melatonin (3) soy+melatonin (4) placebo	232 postmenopausal women	Isoflavone supplement: 80mg	3 months	No significant difference in reduction of hot flashes between placebo, isoflavone only, melatonin only, and isoflavone+melatonin.
Murkies, 1995 59	Randomized trial of soy vs. wheat flour supplement to usual diet	58 postmenopausal women with hot flushes	Soy flour	12 weeks	Both groups had significantly decreased hot flushes compared to baseline, soy did not decrease hot flushes significantly more than wheat.
Burke, 200360	Randomized, double-blind trial. 3 preparations of soy: (1) without isoflavones (2) 42 mg isoflavones/day—LO (3) 58 mg isoflavones/day—HI	241 women with vasomotor symptoms	Soy Protein: 25g daily-3 preparations with varying levels of isoflavones	2 years	All groups had significantly reduced hot flashes compared to baseline. No significant differences in hot flashes were observed between the groups.

RCT=Randomized-controlled trial (double-blind, placebo controlled)