Systematic reviews and recent studies indicate that Ginkgo biloba is a promising herbal supplement for improving cognition and function in people with age-related dementia (1,2,3). Preliminary research also points to a role for Ginkgo in some eye conditions. Small controlled trials report that Ginkgo improves pre-existing visual field damage in patients with normal tension glaucoma (4), and long distance visual acuity in AMD patients (5).

The beneficial effects of Ginkgo are attributed to its antioxidant properties and ability to enhance cerebral blood flow. There have been reports linking Ginkgo use with spontaneous bleeding or increased bleeding post-surgically (6). However, it is not always clear from these observations whether ginkgo is contributory or simply associated with these occurrences. According to the conclusions of a recent independent and systematic review of the world's medical literature, the probability of Ginkgo causing such bleeding is "unlikely" (7). However the use of Ginkgo at effective levels (120 mg. or higher) along with anti-coagulation or anti-platelet medications could raise the risk of increased bleeding (2) and likely should be monitored with occasional bleeding time tests. Some experts also believe that Ginkgo, like aspirin, should be discontinued between 36 hours and 14 days before surgery.

Medical experts at the University of Exeter, England searched 5 medical databases for cases reports in which bleeding had been observed in patients who had been using some type of preparation containing Ginkgo. The review was initiated in recognition that numerous published articles and reviews on Ginkgo have acknowledged the theoretical possibility that use of Ginkgo extract as a medicine or dietary supplement may result in bleeding due to Ginkgo's well-documented mechanism of inhibiting platelet aggregation.

Twelve case reports met the authors' inclusion criteria. They examined each of these published reports and scored them according to a previously published scoring scale that rates the reliability of each report based on the amount of evidence. This scale classifies each study into one of 3 categories: "not able to evaluate" - the report contains inadequate information to assess the likelihood of a causal relationship; "possible" - the report provides some evidence for a causal relationship but there may be other causes of the event (e.g., the use of anti-coagulant drugs); and "likely" - the report is well documented and appears to provide reliable evidence for a causal relationship.

The authors concluded that the evidence in the reports was "far from compelling." In all but one of the cases the evidence for causality did not rate higher than "possible". They noted that with such widespread use of Ginkgo - 5 million unit doses are sold each year in Germany alone - the number of case reports of bleeding was "extremely low."

The authors discuss the apparent contradiction in the case reports and the results from controlled clinical trials. The researchers concluded that since there have been no cases of bleeding observed in 9772 subjects in 44 controlled clinical trials that they reviewed, that the probability of such cases happening with Ginkgo users was "unlikely."

"Case reports can rarely be conclusive," they write, "and under-reporting can significantly distort the picture. While the case reports suggest that [Ginkgo] does affect blood coagulation, the controlled clinical trials do not support such a hypothesis. Weighing the conclusiveness of this evidence, it seems likely that the case reports are 'false positives' and that the controlled trials depict the true situation: Ginkgo biloba does not cause bleeding abnormalities."

References

1. Birks J, et al. Ginkgo biloba for cognitive impairment and dementia. The Cochrane Database of Systematic Reviews Issue 4. Art. No.: CD003120. DOI: 10.1002/14651858.CD003120, 2002.
2. Sierpina VS, et al. Ginkgo biloba.Am Family Physician 68:923-6, 2003.
3. Ercoli L, et al. Society for Neuroscience Meeting, New Orleans, November, 2003.
4. Quaranta L, et al. Effect of Ginkgo biloba extract on preexisting visual field damage in normal tension glaucoma. Opthalmol 110:359-62, 2003.
5. Fies P, et al. Ginkgo extract in impaired vision-treatment with special extract EGb 761 of impaired vision due to dry senile macular degeneration. Wien Med Wochenshr 152:423, 2002.
6. Fraunfelder FW. Ocular adverse drug reactions and the National Registry of Drug-induced Ocular Side Effects. Insight.29(2):7-11, 2004.
7. Ernst E, et al. Does Ginkgo biloba increase the risk of bleeding? A systematic review of case reports. Perfusion 18-52-56, 2005.

Some SBH multi formulas include small amounts of ginkgo for the unique bioflavonoids it contributes. The potency of ginkgo in these multis represents 1/6-1/3 of the minimum clinical level - amounts highly unlikely to pose any safety risk. Optic Nerve Formula contains 120 mg of ginkgo - the amount that has been shown in research to support normal blood flow to the eyes. The label of this product notes: "Contains Ginkgo biloba, which may affect platelet aggregation. If you are taking anticoagulant or anti-platelet medication, ask your physician."