Recent studies have shown that Ginkgo Biloba can be effective in reducing the severity of acute mountain sickness. In a double-blind, placebo-controlled study, 40 volunteers who lived at 1400m were taken rapidly to 4300m and spent the night. Compared to those taking the placebo, the subjects taking the ginkgo had half the incidence of AMS symptoms, and those who did become ill had far milder symptoms.

The protocol involved taking 120 mg of the ginkgo (or the placebo) twice daily for 5 days prior to the ascent, and continuing at altitude.

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.

Native to China, exported to the world as an ornamental street tree. Its common English name is the maidenhair tree. Has fan-shaped leaves that turn colors from light green in the spring to yellow in autumn. Their seeds stink pretty bad when they start to rot on the ground. Despite the stench, the seed is a delicacy in some countries. The tree is the only living representative of its family and order, thus the tree is said to be a "living fossil."