Isoflavones improve plasma homocysteine status and antioxidant defense system in healthy young men at rest but do not ameliorate oxidative stress induced by 80% VO2pk exercise.

AIMS

(1) Determination of whether isoflavones, as antioxidants and estrogen-like substances, reduce the atherosclerotic process. (2) Assessment of isoflavone anti-atherosclerotic effectiveness by means of measuring plasma markers of atherosclerosis: homocysteine (Hcy), antioxidant status, and lipid peroxidation. (3) Testing of isoflavone antioxidant effectiveness in the presence and absence of oxidative stress induced by exercise.

METHODS

Thirty subjects paired by aerobic fitness level were randomly assigned to either a placebo or high-genistein isoflavone extract (HGI, 150 mg/day) treatment. Blood samples were collected before and within 5 min, after 30 min at 80% peak oxygen consumption (VO(2)pk) exercise, and before and after 4-week supplementation.

RESULTS

Plasma genistein and daidzein were significantly increased by 4-week HGI supplementation before and after exercise (p < 0.05). HGI decreased pre-exercise (pre-ex) plasma malondialdehyde (MDA) (p < 0.05) and Hcy (p = 0.01), and increased pre-ex blood total glutathione (TGSH) (p = 0.01), but did not diminish the increase of MDA and the decrease of TGSH due to the exercise. Furthermore, HGI supplementation enhanced pre-ex total antioxidant capacity (p < 0.05), but did not influence plasma vitamin C and E and uric acid concentrations.

CONCLUSION

Isoflavones reduce plasma Hcy and have antioxidant activity in healthy young men. However, the effect of isoflavones on antioxidant systems may not be potent enough to diminish an abrupt surge of oxidative stress due to acute exercise.