Isoflavones restore altered redox homeostasis of
antioxidant enzymes in healthy young men undergoing
80% Peak Oxygen Consumption (VO
2
pk) exercise
Chung-Yen Chen
a,
*, Raga M. Bakhiet
a
, Vanessa Hart
a
, Golde Holtzman
b
a
Department of Human Nutrition, Foods, and Exercise, Virginia Polytechnic Institute and State University,
Blacksburg, VA 24061-0430, USA
b
Department of Statistics, Virginia Polytechnic Institute and State University,
Blacksburg, VA 24061-0430, USA
Received 17 June 2003; received in revised form 17 November 2003; accepted 9 February 2004
Abstract
Isoflavones have potential health effects attributed to their antioxidant activity. The objective of this
study was to test whether isoflavones affected the enzymatic antioxidant defense system in young men
undergoing 80% peak oxygen consumption (VO
2
pk) exercise on cycle ergometer for 30 minutes.
Fifteen pairs of subjects were randomly assigned to receive either high-genistein isoflavone extract
(HGI, 150 mg/day) or placebo. Subjects engaged in two 30-minute sessions of exercise before and
after 4 weeks of supplementation. There was a significant increase in plasma genistein and daidzein
concentrations (499 and 415 ng/mL, P Ͻ 0.0001) after the supplementation, demonstrating isoflavone
bioavailability. Isoflavones significantly increased pre-exercise erythrocyte superoxide dismutase
(SOD) activity (P Ͻ 0.001). Furthermore, isoflavones prevented the exercise-induced decrease in
activities of glutathione peroxidase (GPx) and catalase (CAT) and the increase in antioxidant enzyme
(AE) ratio, maintaining all at pre-exercise levels. Our results suggest that isoflavones can restore the
altered redox homeostasis of antioxidant enzymes due to exercise. © 2004 Elsevier Inc. All rights
reserved.
Keywords: Catalase; Exercise; Glutathione peroxidase; Humans; Isoflavones; Superoxide dismutase
* Corresponding author. Current address: Jean Mayer USDA Human Nutrition Research Center on Aging,
Tufts University, Boston, MA 02111. Tel.: (617) 556-3116; fax: (617) 556-3344.
E-mail address: oliver.chen@tufts.edu (C.-Y. Chen).
www.elsevier.com/locate/nutres
Nutrition Research 24 (2004) 347–359
0271-5317/04/$ – see front matter © 2004 Elsevier Inc. All rights reserved.
doi:10.1016/j.nutres.2004.02.001