Table 2.

Summary of randomized controlled trials of soy isoflavones and their metabolites on arterial stiffness.

Subjects	Arterial Stiffness	Intervention	Duration	Change	Blood Pressure	Ref.
105 post-menopausal women	AF-PWV	118 mg isoflavones with 40 g of soy	3 months	8% reduction (not significant)	No significant change	[141]
80 healthy subjects	AF-PWV	80 mg biotin or formonoetin – precursor of genistein and daidzein	6 weeks	3.5% reduction (significant)	No significant change	[12]
25 subjects	AF-PWV	1 g of trans-tetrahydordaidzein – metabolites of daidzein	5 weeks	9.5% reduction (significant)	Significant reduction. Significant change in PWV remained after adjusting for blood pressure	[11]
21 women	SAC	80 mg isoflavones	5-10 weeks	26% improvement (significant)	No significant change	[142]
54 subjects	CAVI	10 mg S-equol	12 weeks	4% reduction (significant)	No significant change	[71]
93 with diabetics (for PWV, subgroup of 35)	cfPWV	90 mg of epicatechin (flavonoid) and 100 mg of soy isoflavones	1 year	Significant reduction after 12 months but not 6 months	No significant change	[9]
40 post-menopausal women using tibolone (20 equol producers and 20 non-producers)	Augmentation index	52g of soy protein and 112 mg of soy isoflavones	8 week cross over trial	No significant change	No significant change	[172]
14 S-equol producers and 14 non producers	cfPWV, EndoPAT Acute effect (24 hours)	80 mg soy isoflavones, 40 mg S-equol	Cross over trial (baseline, 6 and 24 hours)	Soy isoflavones improved cfPWV in S-equol producers only. S-equol did not improve cfPWV	No significant difference	[10]
17 adults at cardio-metabolic risk (12 women and 5 men)	Augmentation index	55 mg genistein, 42 mg daidzein, and 4 mg glycitein	4 weeks	10% reduction in intervention group vs. 8% increase in control group (significant)	Not reported	[243]
20 adults with moderately elevated resting blood pressure (11 women and 9 men)	cfPWV, augmentation index	50g/d soya group: 27.5 mg genistein, 54.5 mg daidzein and 53 mg glycitein; 25g/d soya group: 13.8 mg genistein, 27.3 mg daidzein and 26.5 mg glycitein; control: 0	6 week cross over trial	No significant difference	Brachial diastolic blood pressure is 1.5 mmHg lower in the 50g/d soy group than control group.	[143]

Reduction in AF-PWV and CAVI means improvement of arterial stiffness whereas increase in SAC means improvement of arterial stiffness. Change in blood pressure is important because a major determinant of AF-PWV is blood pressure.

AF-PWV: Aorto-femoral pulse wave velocity, cfPWV: carotid-femoral pulse wave velocity, PWV: pulse wave velocity, SAC: Systemic arterial compliance, CAVI: Cardio-ankle vascular index.