There was an actual human clinical trial conducted with ginko by the high altitude medicine group (a group of expert MD's in high altitude medicine) and they found it to be effective at treating AMS:
Ginko Biloba for the prevention of AMS
More work is being done in the use of herbal preparations to prevent AMS. In a recent double-blind, placebo-controlled study study, 40 volunteers who lived at 1400m (4,597 ft) were taken rapidly to 4300m (14,110 ft) and spent the night. Compared to those taking placebo, subjects taking ginko had half the incidence of AMS symptoms, and those on ginko who did become ill had far milder symptoms.
Protocol: ginko biloba 120 mg orally twice a day, starting 5 days prior to the ascent, and continuing at altitude.
Results: AMS defined as ESQ-III score > 0.7 and Lake Louise Score > 3
Subjects with AMS: 7 of 21 on ginko vs. 13 of 19 on placebo
Mean Lake Louise Scores 3.9±0.6 on ginko vs. 6.2±0.9 on placebo; mean ESQ-III scores 0.77±0.20 on ginko vs. 1.59±0.32 on placebo
Conclusion: Ginko biloba was effective at preventing AMS symptoms.
References
Maakestad K, Leadbetter G, Olson S, Hackett P. Ginko biloba reduces incidence and severity of acute mountain sickness.(Abstract) Proceedings Wilderness Medical Society Summer Conference, Park City, Utah. August 9-12, 2000.
