Abstract
Background/Objectives:
Although observational studies suggest that soy foods or isoflavones are cardio-protective, clinical trials on whole soy or isoflavone daidzein (one major isoflavone and the precursor of equol) on blood pressure (BP) and endothelial function (EF) are few and have not been specifically conducted among equol producers, a population most likely to benefit from soy treatment.
Subjects/Methods:
We performed a 6-month double-blind, randomized, placebo-controlled trial to examine the effect of whole soy (soy flour) or purified daidzein on BP and EF in prehypertensive or untreated hypertensive postmenopausal women verified to be equol producers. A total of 270 eligible women were recruited and randomized to either one of the three treatment groups, 40 g soy flour (whole soy group), 40 g low-fat milk powder+63 mg daidzein (daidzein group) or 40 g low-fat milk powder (active control group) daily, each given as a solid beverage powder for 6 months. The primary outcome measures were 24 h ambulatory BP (ABP) and EF assessed by flow-mediated dilation using brachial artery ultrasound.
Results:
A total of 253 subjects completed the study according to protocol. Urinary isoflavones indicated good compliance with the interventions. Intention to treat and per-protocol analysis indicated that there was no significant difference in the 6-month changes or % changes in parameters of ABP and brachial flow-mediated dilation among the three treatment groups. A further subgroup analysis among hypertensive women (n=138) did not alter the conclusions.
Conclusions:
Whole soy and purified daidzein had no significant effect on BP and vascular function among equol-producing postmenopausal women with prehypertension or untreated hypertension.
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Acknowledgements
Professor Suzanne C Ho, Dr Liu zhao-min, Prof Chen Yu-ming and Prof Jean Woo conceptualized and designed the trial and obtained the grant. Dr Liu zhao-min conducted data collection, analyzed the data and drafted the manuscript. Professor Tomlinson provided assistance in the primary outcome measures of 24 ABP. Professor Yu-ming Chen helped in urinary analysis of isoflavones and in dietary assessment. Professor Kenneth conducted the randomization and supplement labeling. Dr Stella Ho helped in training and consultation in ultrasound measurement of brachial EF of FMD.
Trial registration. The trial was registered in ClinicalTrials.gov with identifier of NCT01270737. (URL: http://clinicaltrials.gov/ct2/show/NCT01270737)
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The authors declare no conflict of interest. Neither the RGC-GRF nor the soy and dairy company had any role in the design and conduct of the study, the collection, analysis and interpretation of the data, or in the preparation, review or approval of the manuscript.
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Liu, ZM., Ho, S., Chen, YM. et al. Effect of whole soy and purified daidzein on ambulatory blood pressure and endothelial function—a 6-month double-blind, randomized controlled trial among Chinese postmenopausal women with prehypertension. Eur J Clin Nutr 69, 1161–1168 (2015). https://doi.org/10.1038/ejcn.2015.24
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DOI: https://doi.org/10.1038/ejcn.2015.24
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