Supplements made from ginkgo biloba leaves are often used as an herbal medicine to help preserve memory and eye health in older people and improve circulation, particularly in the legs. Ginkgo is not approved by the U.S. Food and Drug Administration to treat any medical condition, and clinical studies point to serious concerns with some of the side effects and potential problems. Talk to your doctor about the risks and benefits of ginkgo before taking it.
Ginkgo can help improve circulation in some people due to its ability to thin the blood. It's due to this mechanism that the supplement can cause internal bleeding, particularly in the eye and brain. Don't take ginkgo if you're taking other blood thinners. The University of Maryland Medical Center recommends stopping ginkgo at least 36 hours before surgery and dental procedures to minimize the risk of excess bleeding.
Ginkgo may increase stroke risk, particularly in older individuals. A study published in "Neurology" in 2008 focused on the use of ginkgo to delay cognitive impairment in participants 85 and older. The 42-month-long study found that seven participants in the group that received ginkgo biloba had a stroke or transient ischemic attack, compared to none in the placebo group. While the study results don't prove that ginkgo supplements increase stroke risk, it's wise to take this information into consideration, particularly if you're over the age of 84 or if you have other stroke risk factors, such as high blood pressure or heart disease.
Liver and Thyroid Cancers
A 2013 report issued by the National Toxicology Program found that ginkgo biloba extract increased the risk of liver and thyroid cancers in laboratory rodents. Over a three-month study period, male and female rats and male mice given ginkgo biloba had higher rates of thyroid cancers, and male and female mice had higher rates of liver cancers after taking ginkgo. It's unknown whether these cancer risks carry over to humans, but it's something to consider if you're thinking about starting ginkgo supplements.
Don't take ginkgo with other medications that increase the risk of bleeding, such as blood thinners, aspirin and ibuprofen. Ginkgo can lower blood sugar and insulin levels, so talk to your doctor about the safety of the supplement if you're diabetic or take medications to lower your blood sugar. Taking ginkgo with antidepressants classified as selective serotonin reuptake inhibitors, or SSRIs, increases your risk of serotonin syndrome. Don't take ginkgo in combination with alprazolam for anxiety, as it can decrease the medication's effectiveness.
Poisoning and Allergic Reactions
Commercial ginkgo biloba supplements are made from an extract of the leaf of the plant. Consuming the fruit can lead to severe allergic reactions, particularly if you're allergic to poison ivy, oak or sumac, mango rind or cashew shell oil, cautions MedlinePlus. The seeds are especially dangerous and can lead to seizures, difficulty breathing and even death. If you do decide to take ginkgo supplements, ask your doctor or pharmacist to recommend a dosage and reputable brand.