Excessive bleeding has been reported in a few individuals taking ginkgo,122, 123 although a cause/effect relationship was not proven. A review of 18 randomized controlled trials with a total of 1,985 adults concluded that it is unlikely that taking ginkgo increases the risk of bleeding.124 In addition, two elderly individuals with well-controlled epilepsy developed recurrent seizures within two weeks after starting ginkgo.125 Mild headaches lasting for a day or two and mild upset stomach have been reported in a small number of people using ginkgo.
Ginkgo leaves are known to contain a group of potentially toxic constituents known as alkylphenols. To reduce the potential for adverse effects, the German Commission E Monograph requires that ginkgo products for human consumption contain less than 5 parts per million of alkylphenols.126
One small clinical trial found that ginkgo supplementation for three months increased secretion of insulin by the pancreas, but did not affect blood glucose levels, in healthy young adults.127 These results suggest that the participants may have developed an insensitivity to insulin, a potential concern because insulin insensitivity may be a precursor to type 2 diabetes. However, this trial does not prove that ginkgo causes insulin insensitivity, nor does it prove that long-term ginkgo supplementation increases the risk for any disease. In addition, the results of this trial are not consistent with other research on ginkgo. Larger and more rigorously designed clinical trials of ginkgo supplementation have found no significant adverse effects after as many as 12 months of supplementation.128
People should seek an accurate medical diagnosis prior to self-prescribing ginkgo. This is especially important for the elderly, whose circulatory conditions can involve serious disease, and for people scheduled for surgery, as ginkgo may affect bleeding time.
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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2015.