Oral antioxidant supplementation does not prevent acute mountain sickness: double blind, randomized placebo-controlled trial.

Double-blind, randomized, placebo-controlled trial in healthy lowland volunteers enrolled in the Apex 2 expedition to Bolivia. Participants had not been above 1500 m in the preceding 3 months and were exposed acutely to 5200 m at the Chacaltaya Research Laboratory; 41 participants were randomized to the antioxidant arm.

The active regimen was a daily oral antioxidant combination in sealed capsules: 1 g L-ascorbic acid, 400 IU a-tocopherol acetate, and 600 mg alpha-lipoic acid, taken in four divided doses per day. Treatment began on the day of travel to high altitude and continued for 14 days after ascent, compared with placebo/placebo.

Oral antioxidant supplementation did not prevent acute mountain sickness or improve related physiologic measures at 5200 m. On Day 2, acute mountain sickness by Lake Louise Consensus symptom score > 3 occurred in 25/36 (69%) antioxidant participants versus 23/35 (66%) placebo participants (P = 0.74). There were no differences in AMS severity by VAS, pulmonary artery pressure, or oxygen saturation. The authors concluded that this antioxidant combination is not effective for AMS prophylaxis.

The primary outcome was available for only 36 of 41 participants in the antioxidant arm. The trial was conducted in a small, specific expedition setting with rapid ascent to 5200 m, so generalizability is limited. Frequent high-altitude evacuations for severe AMS and the presence of another active comparator arm add complexity to interpretation.