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Atherosclerosis. 1999 Jul;145(1):167-72.

Isoflavonoids do not inhibit in vivo lipid peroxidation in subjects with high-normal blood pressure.

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1
University of Western Australia Department of Medicine and the Western Australian Heart Research Institute, Royal Perth Hospital, Australia. jonathan@cyllene.uwa.edu.au

Abstract

The isoflavonoids genistein and daidzein have been shown to have antioxidant activity in vitro, but their effects on in vivo oxidation have not been assessed. The newly described F2-isoprostanes are believed to currently represent the best available marker of in vivo lipid peroxidation. Therefore we have assessed the effects of a 55 mg daily isoflavonoid supplement on urinary F2-isoprostane concentrations in subjects with high-normal blood pressure (BP). A total of 59 subjects completed an 8-week parallel design, randomized, double blind, and placebo-controlled study. F2-isoprostanes, isoflavonoids and creatinine were measured in 24-h urine samples taken at baseline and at the end of the intervention. There were significant increases in urinary excretion of genistein (5.22+/-0.75 mg/day, P < 0.0001) and daidzein (2.53+/-0.43 mg/day, P < 0.0001) in the group taking the isoflavonoid supplement. Creatinine excretion was significantly correlated with F2-isoprostanes at baseline (r = 0.45, P < 0.01). After adjustment for baseline values, there was no significant difference between groups in creatinine adjusted post-intervention F2-isoprostane concentrations (P = 0.74). In addition, changes in genistein and daidzein excretion were not significantly correlated with changes in F2-isoprostanes in the isoflavonoid treatment group. These results are not consistent with the suggestion that the two soy derived isoflavonoids have in vivo antioxidant activity at a level of intake achievable by dietary means and in subjects with high-normal BP.

PMID:
10428307
[Indexed for MEDLINE]

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