SALT LAKE CITY - This spring, 100 test subjects are scheduled to be driven up the slopes of Hawaii's Mauna Kea volcano to try to pin down whether an inexpensive herbal extract can protect climbers, skiers and other outdoor enthusiasts from the debilitating effects of high altitude.
Ginkgo biloba, an extract of the leaf of the ginkgo biloba tree, seemed like the answer to mountaineers' prayers after a 1996 French study showed it provided remarkable protection against altitude sickness for climbers on a Himalayan expedition.
Two U.S. researchers, inspired to study gingko after reading the French study, have not duplicated the startling results, but are intrigued enough to continue investigating.
In the French study, researchers divided a group of 44 climbers, who all had experienced altitude sickness on previous expeditions, into two groups. One group received 160 milligrams of ginkgo extract daily while slowly climbing to a base camp of 14,700 feet and making further ascents to various altitudes. The other group took a placebo.
Only 14 percent of the climbers who took ginkgo experienced one or more symptoms of altitude sickness, compared to 82 percent in the placebo group. None of the ginkgo group developed the full symptoms of acute mountain sickness, while 41 percent of those taking placebo did.
The ginkgo group, which happened to contain two smokers and three ex-smokers, also had fewer cold-related vascular problems. There were no smokers or ex-smokers in the placebo group.
When Janet Onopa of the University of Hawaii told a class of first-year medical students that the findings of the extraordinary French study - which no one was using - could easily be replicated in Hawaii, a student volunteered to help do just that.
"I'm a climber," he told Onopa after the class. "I get sick. I will work my butt off on it, if you are willing to do it."
Onopa, the student and others studied whether ginkgo would help during rapid ascent. Their subjects started taking ginkgo a day before they were driven from sea level to the 13,796-foot summit of Mauna Kea. In the ginkgo group, just 17 percent developed acute mountain sickness, while 64 percent of the placebo group did. But the small number of subjects - a total of 26 in both groups - prevented the researchers from drawing definitive conclusions.
The climbing student has been testing the use of gingko in a study in Nepal, but the results don't look as promising, Onopa said.
"Research is like that," she said. Ginkgo, commonly prescribed by homeopaths as a treatment for Alzheimer's disease, may still be an altitude panacea, "but until we get large numbers, we just don't know. It will take another 50 years to sort it out because it's a complicated compound."
Onopa's next study, to be conducted in the spring on Mauna Kea with 100 subjects, will compare the use of ginkgo to the sulfonamide drug acetazolamide, marketed as Diamox, which is used to accelerate acclimatization.
Meanwhile, Onopa has no hesitation in using ginkgo herself. "Its side-effect profile is very benign and it's very inexpensive," she said.
Those taking aspirin and blood thinners should avoid taking ginkgo, as it is thought that ginkgo could induce internal bleeding, although bleeding has not occurred in trials.
Peter Hackett, president of the International Society for Mountain Medicine, also began studying ginkgo after reading the French study.
"I read it and I couldn't believe it," said Hackett, who is based in Ridgeway, Colo. "I had to do my own study."
Hackett had subjects take ginkgo five days before a quick ascent of 14,110-foot Pike's Peak. Those in the ginkgo group were half as likely to experience acute mountain sickness as those taking placebo. But in September, when Hackett compared the use of ginkgo, taken beginning three days before ascent, to low-dose acetazolamide, the drug prevented acute mountain sickness, but ginkgo did not.
"That's science for you," said Hackett, who is now designing a third study. He also believes larger studies are needed to nail down ginkgo's effectiveness.
Hackett still advises climbers who consult him to try ginkgo.
"Clearly it helps some people and it's safe," said Hackett, who included information on ginkgo while lecturing at the Special Operations Medical Association conference in Tampa, Fla. "It doesn't have as many side effects as Diamox. Since it's not harmful, and there are studies showing it works for some people, it's worth a try."
Many climbers who consult him write back to laud ginkgo, Hackett said.
For those sleeping at 8,000 feet or higher, or known to be particularly susceptible to altitude sickness, Hackett advises taking 100 mg of ginkgo twice daily, beginning five days before ascent.