Exposure to isoflavone-containing soy products and endothelial function: a Bayesian meta-analysis of randomized controlled trials.
OBJECTIVE
To determine whether and to what degree exposure to isoflavone-containing soy products affects EF. Endothelial dysfunction has been identified as an independent coronary heart disease risk factor and a strong predictor of long-term cardiovascular morbidity and mortality. Data on the effects of exposure to isoflavone-containing soy products on EF are conflicting.


RESULTS
A comprehensive literature search was conducted using the PUBMED database (National Library of Medicine, Bethesda, MD) inclusively through August 21, 2009 on RCTs using the keywords: soy, isoflavone, phytoestrogen, EF, flow mediated vasodilation, and FMD. A Bayesian meta-analysis was conducted to provide a comprehensive account of the effect of isoflavone-containing soy products on EF, as measured by FMD. A total of 17 RCTs were selected as having sufficient data for study inclusion. The overall mean absolute change in FMD (95% Bayesian CI) for isoflavone-containing soy product interventions was 1.15% (-0.52, 2.75). When the effects of separate interventions were considered, the treatment effect for isolated isoflavones was 1.98% (0.07, 3.97) compared to 0.72% (-1.39, 2.90) for isoflavone-containing soy protein. The models were not improved when considering study-specific effects such as cuff measurement location, prescribed dietary modification, and impaired baseline FMD.


CONCLUSIONS
Cumulative evidence from the RCTs included in this meta-analysis indicates that exposure to soy isoflavones can modestly, but significantly, improve EF as measured by FMD. Therefore, exposure to isoflavone supplements may beneficially influence vascular health.
Beavers
D P
DP
Department of Biostatistical Sciences, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
Beavers
K M
KM
Miller
M
M
Stamey
J
J
Messina
M J
MJ
D000368:Aged; D001499:Bayes Theorem; D002318:Cardiovascular Diseases / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D004032:Diet; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000503:physiopathology; D019317:Evidence-Based Medicine; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage* / Q000032:analysis; D008297:Male; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D045730:Soy Foods / Q000032:analysis; D016896:Treatment Outcome; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000008:administration & dosage* / Q000032:analysis
D007529:Isoflavones; D014665:Vasodilator Agents