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There is insufficient information available to justify special consideration for those taking blood pressure medication. The large Shanghai Women's Health Study which included >45,000 women aged 40-70 years with no history of hypertension, diabetes, or cardiovascular disease found that soy protein intake was inversely associated with both systolic BP (P for trend=0.01) and diastolic BP (P for trend=0.009) (Yang et al. 2005). With respect to intervention studies, a 2003 review of studies investigating soy and blood pressure summarized that there is convincing evidence for a blood pressure lowering effect from clinical trials of soy foods and protein isolates but in contrast, phytoestrogen supplements (containing extracted isoflavones) do not reduce blood pressure (West et al. 2003), a finding most relevant to soy supplements. The 2003 review further summarized that few studies have examined effects of soy products on blood pressure in hypertensive individuals (West et al. 2003). Since this review, Welty et al. (2007) conducted a RCT of 60 normo-, pre- and hyper-tensive postmenopaual women and demonstrated that the observed reducing effect of consuming soy nuts (equivalent to 25 g soy protein and 101 mg AIE) for 8 weeks on systolic and diastolic blood pressure was greater in the pre- and hyper-tensive postmenopausal women. However, in another study of hypertensive adults (15 postmenopausal women, 26 men), 3 months of soy cereal consumption (40 g soy protein, 118 mg isoflavones) reduced daytime blood pressure but did not change average 24 hr ambulatory blood pressure parameters (Teede et al. 2006).
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