Soy isoflavones do not attenuate oxidative stress in postmenopausal women

Postmenopausal women are at risk for chronic diseases, may be a as a result of increased oxidative stress. Our hypothesis is that that soy isoflavones would attenuate the anticipated increase in oxidative stress in postmenopausal women. The parent project recruited healthy women for a randomized, double‐blind, 36 mo ‐clinical trial designed to examine the effect of two doses of soy isoflavones on bone. In this ancillary study, we collected data on 122 healthy postmenopausal women (55y, BMI of 24.9 m/Kg 2 ) who consumed placebo or soy isoflavones (80 or 120 mg/d) for 12 mo. We collected data on antioxidant enzymes (catalase, superoxide dismutase, and glutathione peroxidase), oxidative stress indices (oxidized LDL, urinary isoprostanes, protein carbonyls, urinary 8‐hydroxy‐2′‐deoxyguanosine), and iron status indices at baseline, 6 mo, and 1 year. We ran a repeated measures analysis of variance to determine a possible treatment effect over the 12 mo period. After taking into consideration of baseline values, there were no significant differences among the treatments over time on any antioxidant enzymes or oxidative stress indices. Only the transferrin saturation was significantly affected (time × treatment; P=0.021) by the isoflavone treatment. In conclusion, long‐term soy isoflavon consumption had no significant effect on oxidative stress in postmenopausal women. Supported by AHA and NIAMS.