Natural Health Products

Numerous studies of ginkgo have been done for a variety of conditions. Among the most widely researched are dementia, memory impairment, intermittent claudication (leg pain caused by narrowing arteries), and tinnitus.

A study funded by the United States National Center for Complementary and Alternative Medicine (NCCAM) of the well-characterized ginkgo product EGb-761 found it ineffective in lowering the number of cases of dementia and Alzheimer’s disease in the elderly, slowing cognitivecognitiverelating to the ability to think, reason, remember, and discern decline, lowering blood pressure, or reducing the number of cases of high blood pressure. In this clinical trial, known as the Ginkgo Evaluation of Memory study, more than 3,000 volunteers age 75 and over took 240 mg of ginkgo daily for an average of approximately 6 years.

Some smaller studies for memory enhancement have had promising results, but a trial sponsored by the National Institute on Aging of more than 200 healthy adults over age 60 found that ginkgo taken for 6 weeks did not improve memory.

Overall, ginkgo has not yet been found to have a significant effect on symptoms of intermittent claudication, although several small studies have found modest improvements. There is conflicting evidence on whether ginkgo is effective in treating tinnitus.

Side effects of ginkgo may include headache, nausea, palpitations, gastrointestinal upset, constipation, diarrhea, dizziness, or allergic skin reactions. Restlessness, vomiting, weakness, and lack of muscle tone have also been reported with large doses. More severe allergic reactions have occasionally been reported.

Ginkgo may increase bleeding risk, so people who take products that affects coagulation (e.g., anticoagulants, antiplatelets, NSAIDs) or have bleeding disorders, or have scheduled dental procedures should not take this product. Gingko leaf extractextractto get, separate, or isolate a desired active ingredient should be discontinued for at least 2 weeks prior to elective surgery.

Fresh (raw) ginkgo seeds contain large amounts of a chemical called ginkgotoxin, which can cause serious adverse reactions – even seizures and death. Roasted seeds can also be dangerous. Products made from standardized ginkgo leaf extracts appear to contain little ginkgotoxin and appear to be safe when used orallyorallyto be taken by mouth (swallowed) and appropriately.

National Toxicology Program (NTP) studies showed that rats and mice developed tumours after being given a specific ginkgo extract for up to 2 years. Further studies are needed to find out what substances in ginkgo caused the tumours and whether taking ginkgo as a dietary supplement affects the risk of cancer in people.

There may be an interaction with gingko leaf extract and any of the following:

• anticonvulsants (e.g., gabapentin, phenytoin)
• anticoagulants/antiplatelet drugs (e.g., aspirin, clopidogrel, low molecular weight heparin)
• antidepressants
• antidiabetic drugs
• atorvastatin
• buspirone
• certain drugs metabolized by the liver (e.g., acetaminophen, diazepam, omeprazole, ibuprofen, codeine, clarithromycin)
• efavirenz
• risperidone
• seizure threshold lowering drugs (e.g., bupropion, penicillin)
• simvastatin
• trazodone
• warfarin

Consult your health care provider if you’re taking 4–6 grams of ginkgo daily for more than 8 months, or 6–9 grams daily for more than 6 weeks, or 9–12 grams daily for more than 4 weeks.

If you are taking medication for diabetes, high blood pressure, or seizures, or if you are pregnant or breast-feeding, talk to your health care provider before using ginkgo leaf extracts to make sure the product is safe for you. Couples attempting to conceive should also consult their health care provider before starting on ginkgo leaf extract.

Before taking any new medications, including natural health products, speak to your physician, pharmacist, or other health care provider. Tell your health care provider about any natural health products you may be taking.