Donald E. Roberts

Oxidative Stress in Humans Training in a Cold, Moderate Altitude Environment and Their Response to a Phytochemical Antioxidant Supplement

OBJECTIVE This study examined the effectiveness of an antioxidant mixture containing vitamin E, beta-carotene, ascorbic acid, selenium, alpha-lipoic acid, N-acetyl 1-cysteine, catechin, lutein, and lycopene to reduce oxidative stress in US Marines undergoing 24 days of cold-weather field training at a moderate altitude. METHODS Forty physically active male volunteers (ages 18-40) were randomly assigned to a treatment (antioxidant) group (n = 21) or a control (placebo) group (n = 19). Breath pentane (BP), serum lipid hydroperoxides (LPO), urine malondialdehyde (MDA), urine 8-hydroxy deoxyguanosine (8-OHdG), ferric-reducing ability of plasma (FRAP), and serum and urine oxygen radical absorption capacity (ORAC) were measured as indicators of oxidative stress and antioxidant status. Urine was sampled at days 0, 12, and 24. Serum and breath were sampled on days 0 and 24. RESULTS Both groups exhibited increased levels of oxidative stress after 24 days of field training, as indicated by an increased LPO, pentane, and 8-OHdG. There was no significant difference between the treatment and placebo groups at day 24; however, there was some indication that test subjects with initially low antioxidant capacity (ORAC) may have benefited from the antioxidant supplement. CONCLUSIONS An increased level of oxidative stress was associated with high levels of physical exertion of training in a cold environment at moderate altitude. The antioxidant mixture tested did not attenuate the mean oxidative stress levels in the entire group of test subjects, but it may have reduced the oxidative stress of some individuals with low initial antioxidant status.

Effect of antioxidant supplementation on urine and blood markers of oxidative stress during extended moderate-altitude training

OBJECTIVE To investigate the increase in oxidative stress during work at moderate altitudes due to additional energy expenditure, tissue anoxia, and UV light exposure. METHODS Thirty US Marine Corps volunteers were divided into placebo (P) and antioxidant supplement (S) groups and tested for markers of oxidative stress before (t0), at the midpoint of (t1), and after (t2) 14 days of winter training at a moderate altitude (approximately 2700 m). The antioxidant supplement consisted of a daily dose of 20,000 IU beta-carotene, 400 IU vitamin E, 500 mg vitamin C, 100 micrograms selenium, and 30 mg zinc. The following markers of oxidative stress were measured: urine thiobarbituric acid reactive substances (TBARSs), urine hydroxynonenal (HNE), urine 8-hydrodeoxyguanosine (8-OHdG), plasma total peroxyl radical trapping potential (TRAP), and plasma lipid hydroperoxides (LPOs). Urine was collected on a 24-hr basis at t0, t1, and t2; blood samples were collected at t0 and t2. RESULTS P group LPOs increased 30% (p < 0.05) between t0 and t2, whereas S group LPOs did not increase. Both groups exhibited significant increases in urine TBARSs, HNE, and 8-OHdG by t2. Urine TBARSs, HNE, and 8-OHdG increased between t0 and t1 in both groups, with the greater increase in the S group. The conflicting results between the plasma and urine markers of oxidative stress may be due to a time-phase relationship. CONCLUSIONS The results of this study suggest that work in a moderate-altitude cold-weather environment is accompanied by increased oxidative stress, despite relatively high intakes of dietary and supplemental antioxidants.