Tuesday, March 07, 2006

Ginkgo protects against altitude sickness

In this study of mountain climbers on a Himalayan expedition, extract of Ginkgo biloba L. (Ginkgoaceae) was significantly more effective than placebo in preventing acute altitude sickness and cold-related vascular problems [Roncin et al., 1996]. At elevations higher than 9,000 feet (3,000 meters), most people experience some degree of altitude sickness, which can cause symptoms such as headache, dizziness, shortness of breath, nausea and vomiting. In addition to oxygen deprivation, people at high altitudes may be also subjected to extreme cold. Cold-related microcirculation disturbances can lead to numbness, tingling, aching and/or swelling of the extremities, with a resulting loss of manual dexterity.

The controlled study involved 44 healthy climbers, all men, who had experienced altitude sickness on previous expeditions. The subjects were randomized into two equal groups. One group received two tablets of standardized ginkgo extract twice a day, a total daily dose of 160 mg, and the other took placebo. Over a period of eight days, the climbers ascended gradually to a base camp with an elevation of about 14,700 feet (4,900 meters), from which they made subsequent ascents to higher altitudes. Symptoms were recorded daily with a 67-item scale called the Environmental Symptoms Questionnaire. Separate analyses were performed of a number of different factors, including cerebral and respiratory altitude sickness symptoms.

According to assessment of cerebral symptoms, none of the climbers who took ginkgo experienced acute mountain sickness, compared to 41 percent of those taking placebo. According to assessment of respiratory symptoms, 14 percent of climbers in the ginkgo group had altitude sickness, compared to 82 percent in the placebo group. These differences were highly significant. Ginkgo was also significantly more effective than placebo in preventing cold-related vascular problems, based on evaluation of functional disabilities and results of plethysmography testing (a measurement of blood flow to the extremities). In addition, only 18 percent of ginkgo subjects reported moderate or severe impairment of diuresis at high altitude, compared to 77 percent of those in the placebo group.

Interestingly, while there were no smokers or ex-smokers in the placebo group, there were two smokers and three ex-smokers in the ginkgo group, a factor which might have been expected to have a negative impact on results with ginkgo. The ginkgo preparation used in the study was EGb 761 (Tanakan®, marketed by Ipsen of Paris, France) a concentrated extract standardized to 24 percent ginkgo flavone glycosides and 6 percent terpene lactones.