Oxidative Stress in Humans during Work at Moderate Altitude

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Abstract
Increased oxidative stress has been associated with work at high altitude; however, it is not known whether oxidative stress is a significant problem at moderate altitudes. The oxidative stress indicators, breath pentane (BP), 8-hydroxydeoxyguanosine (8-OHdG), oxygen radical absorption capacity (ORAC), 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), and lipid peroxides (LPO) were measured in breath, blood and urine samples of U.S. Marines engaged in moderate altitude (∼3000 m) cold weather field training. The test subjects were divided into a placebo and four antioxidant supplement groups (n = 15/group) and received the following supplements for 28 d: 1) vitamin E, 440 α-tocopherol equivalents (α-TE); 2) vitamin A, 2000 retinol equivalents (RE) of β-carotene; 3) vitamin C, 500 mg ascorbic acid; 4) a mixture of 440 α-TE, 2000 RE of β-carotene, 500 mg ascorbic acid, 100 μg selenium and 30 mg zinc daily. Strenuous work (∼23 MJ/d) in cold weather at moderate altitude was accompanied by increases in several indicators of oxidative stress that were not effectively controlled by conventional antioxidant supplements. The group receiving the antioxidant mixture exhibited lower BP (P < 0.05) compared with those receiving single antioxidant supplements; however, not all markers of oxidative stress responded like BP. Because these markers did not respond in the same manner, it is important to include markers from more than one source to assess the effect of supplemental dietary antioxidants.