Ginkgo biloba is one of the most widely used herbal supplements globally, most commonly taken to improve memory and cognitive function. Despite its popularity, it is critical to be aware of its potential negative effects, which can range from mild discomforts to severe and life-threatening complications. The supplement market's limited regulation by bodies like the U.S. Food and Drug Administration (FDA) also means that product purity and safety can vary significantly.
Significant Negative Effects and Safety Concerns
Increased Bleeding Risk
One of the most documented and serious side effects of ginkgo biloba is its potential to increase the risk of bleeding. This effect is attributed to ginkgo's ability to inhibit platelet aggregation, which is a key process in blood clotting. Case studies have reported spontaneous and serious bleeding events, including intracranial hemorrhages (bleeding in the brain), in patients taking ginkgo. This risk is heightened when ginkgo is combined with other medications that also slow blood clotting, such as anticoagulants and NSAIDs. For this reason, healthcare professionals advise stopping ginkgo supplementation at least two weeks before any scheduled surgery.
Seizure Potential
Certain components of the ginkgo tree, particularly ginkgotoxin found primarily in the raw or roasted seeds and unpurified products, can be neurotoxic. This substance is an antivitamin structurally related to vitamin B6 and can induce seizures. While standardized leaf extracts are processed to minimize ginkgotoxin content, contaminated or improperly prepared supplements can still pose a risk. Individuals with a history of epilepsy or other seizure disorders are particularly vulnerable and should avoid ginkgo supplements.
Toxicity from Unprocessed Plant Parts
Beyond the standardized leaf extracts, consuming other parts of the ginkgo plant is highly dangerous. Fresh ginkgo seeds are poisonous and can be fatal if ingested, while eating too many roasted seeds can also cause serious side effects like seizures. The fruit pulp and other crude plant parts also contain toxic compounds that can trigger severe allergic skin reactions and other toxicities.
Adverse Drug and Supplement Interactions
Ginkgo biloba can interact with a wide array of prescription and over-the-counter medications, as well as other herbal supplements, leading to potentially dangerous consequences.
Commonly Interacting Medications:
- Anticoagulants and Antiplatelets: Drugs like warfarin (Coumadin) and clopidogrel (Plavix) can have their blood-thinning effects dangerously amplified by ginkgo, increasing the risk of severe bleeding.
- NSAIDs: Nonsteroidal anti-inflammatory drugs like ibuprofen (Advil) and naproxen can also increase bleeding risk when taken with ginkgo.
- Antidepressants: Certain antidepressants, particularly selective serotonin reuptake inhibitors (SSRIs) like fluoxetine (Prozac) and trazodone, can interact with ginkgo, potentially leading to serotonin syndrome or reduced drug efficacy.
- Diabetes Medications: Ginkgo can interfere with blood sugar control, potentially reducing the effectiveness of diabetes medications and requiring close monitoring.
- Seizure Medications: Ginkgo can lower the effectiveness of anticonvulsants, increasing the risk of seizures.
Common Side Effects
Even in the absence of severe risks, many people experience mild side effects while taking ginkgo leaf extract. These are typically manageable but can be bothersome.
- Headache
- Gastrointestinal upset (nausea, vomiting, diarrhea, constipation)
- Dizziness
- Heart palpitations
- Allergic skin reactions (rash, redness)
Comparison of Ginkgo Product Risks
It is crucial to differentiate between the risks associated with properly processed ginkgo leaf extract and other forms of the plant. The following table outlines the potential risks based on the ginkgo product type.
| Ginkgo Product Type | Key Toxic Components | Associated Risks | Safety Recommendation |
|---|---|---|---|
| Standardized Leaf Extract | Low ginkgolic acids, trace ginkgotoxin | Increased bleeding risk, drug interactions, allergic reactions, mild side effects | Use with caution and consult a doctor, especially if on medication or undergoing surgery |
| Fresh Ginkgo Seeds | High ginkgotoxin, cyanogenic glycosides | Seizures, neurological damage, potential death | DO NOT CONSUME. Poisonous and highly dangerous |
| Roasted Ginkgo Seeds | High ginkgotoxin | Seizures, convulsions | DO NOT CONSUME. Serious side effects with more than 10 seeds |
| Crude Ginkgo Plant | Unregulated levels of ginkgolic acids, ginkgotoxin, other compounds | Allergic reactions, skin rash, internal toxicities, unknown risks | DO NOT CONSUME. Unpredictable and potentially dangerous |
Conclusion: A Supplement with Serious Caveats
While ginkgo biloba is widely available and often perceived as a benign natural remedy, it is associated with significant negative effects that users must consider. The most serious risks include heightened bleeding, which can lead to life-threatening complications, especially when combined with certain medications. Additionally, the presence of ginkgotoxin in improperly processed supplements, particularly the seeds, poses a serious risk of seizures. The lack of rigorous FDA regulation for herbal supplements means product quality is not guaranteed. For anyone considering ginkgo, a thorough discussion with a healthcare provider is essential, especially for individuals with pre-existing conditions or those taking other medications. The National Center for Complementary and Integrative Health offers reliable resources on the safety and efficacy of herbal supplements.
Who Should Avoid Ginkgo Biloba?
Beyond potential drug interactions, certain populations are advised to avoid ginkgo entirely due to an increased risk of adverse effects. This includes pregnant or breastfeeding individuals, children, people with diagnosed bleeding disorders, and those with a history of seizures. Anyone with a known allergy to poison ivy, poison oak, or cashew shell oil may also experience a cross-reaction to ginkgo.
