Improve your memory, circulation and other health factors with ginkgo biloba.
• Ginkgo biloba
• Standardized leaf extracts of ginkgo are antioxidant, anti-inflammatory and improve circulation in the brain.
• The extracts also protect brain cells from beta-amyloid, a misfolded protein that accumulates in the brains of people with Alzheimer’s disease.
• Hardy through Zone 4
It seems fitting that ginkgo (Ginkgo biloba), a species of tree that thrived 65 million years ago and continues to thrive today, is used worldwide to treat conditions associated with aging.
The Chinese treasured the ginkgo tree first for its food, considering the nuts (seed kernels) a delicacy. The first known use of ginkgo as a medicinal plant dates to 2800 b.c. Early on, ginkgo was thought to increase longevity and stamina largely because the tree itself was so hardy. (As a 20th-century testament to its hardiness, the only tree to survive the atomic blast in Hiroshima was a ginkgo that sprouted from its base after its trunk was completely destroyed.) The Chinese also used the seeds to treat venereal disease, asthma, lung congestion, diarrhea and impaired hearing.
In the past half century, ginkgo has been extensively researched in Europe as a treatment for memory loss, dementia, stroke, asthma and tinnitus (ringing in the ears). Today, European physicians prescribe ginkgo more often than any other herb or drug. Ginkgo appears to enhance health in three general ways. It improves circulation and oxygen metabolism. Ginkgo also prevents cell damage by free radicals and reduces blood clotting.
Ginkgo leaves and roots contain flavone glycosides, which consist of a mix of bioflavonoids that are known antioxidants, including quercetin and kaempferol. Ginkgo also contains terpene lactones such as bilobalide and ginkgolides, which have been shown to protect nerve cells, keep blood from clotting and improve blood circulation. Virtually all of the more than 2,600 studies of ginkgo have used an extract of the leaf (EGb) standardized to 24 percent flavone glycosides and 6 percent terpene lactones.
Ginkgo extract is the best treatment known for inadequate blood flow to the brain caused by weakened blood vessels or impaired circulation due to an overproduction of platelet-activating factor (PAF), which activates immune cells responsible for inflammation and blood clotting. Restricted blood flow to the brain is extremely common among the elderly and is characterized by memory loss, decreased alertness, headaches and depression.
Ginkgo improves circulation throughout the body, including the brain, by increasing the tone and elasticity of the blood vessels, and that increased cerebral blood flow apparently improves cognition.
Numerous studies over the last two decades have shown improvements in cognitive functioning. In one study, elderly patients experiencing memory loss, decreased alertness and mood swings were given 160 mg of ginkgo extract daily for a year. In 58 percent of the patients who received the extract, these conditions improved, compared to 43 percent of the placebo group.
A review study, published in Pharmacopsychiatry in 2010, found that EGb is effective in dementia when given for six months. A recent experiment compared EGb to donepezil (Aricept), a leading Alzheimer’s drug, and found that the herb extract was comparable to the drug for symptoms of dementia. Studies also have shown that ginkgo extracts improve brain cell function and message transmission speed.
Not all of the ginkgo science is quite so positive, however. In the area of dementia, results have been inconsistent. A study done at Oregon State University tested EGb for preventing progression to cognitive decline in normal elderly people aged 85 and older. According to the raw data, EGb showed no benefit. However, when the results were assessed based on who actually took their EGb, the supplement did show a protective effect. Maybe those who needed it the most were the most likely to forget to take it! Another paper in the Journal of the American Medical Association similarly reported that 240 mg daily of EGb did not lessen cognitive decline in older adults with normal cognition.
In most cases, ginkgo does not produce immediate results. Most studies note improvement after one month of taking 120 to 160 mg of ginkgo extract daily with benefits increasing further at three and six months.
When a person with asthma is exposed to an allergen such as pollen, house dust or animal dander, the immune system responds by releasing histamine, PAF, and other substances; these in turn stimulate a copious secretion of mucus and inflammation that narrows the bronchial passages. Ginkgolides may relieve these conditions by inhibiting inflammation and improving lung function, although more research is needed to fully determine ginkgo’s role in the treatment of inflammatory responses with respiratory allergies.
A double-blind trial involving eight asthmatic patients who were given either a standardized mixture of ginkgolides or a placebo and then asked to inhale allergens, researchers reported that patients who took the ginkgo had a “significantly inhibited response to allergens” compared to those who received the placebo.
Recent research from Turkey shows that ginkgo alleviates virtually all established chronic negative changes of the lung in mouse asthma. In 2011, researchers tested, in animals, a mixture of EGb, the carotenoid antioxidant astaxanthin and vitamin C in respiratory inflammation (the underlying cause of most asthma), and the supplement combination performed better than ibuprofen.
British scientists looked at a multiherb mixture containing EGb for treating asthma. They found no improvement in people’s lung function from the formula, but important measures of patient-centered outcomes, such as asthma health status, asthma control and coughing improved. Overall, ginkgo for asthma looks promising, but the jury is still out with its final ruling.
When blood platelets encounter PAF, they change shape and begin sticking together. Clotting under normal circumstances, such as when one cuts a finger, is a welcome and expected response, but when platelets are chronically sticky, they slow blood flow, which can lead to increased deposits of plaque on the walls of blood vessels. The resulting decrease in circulation can lead to heart disease, stroke or painful cramping of the legs during exercise. Ginkgolides, which keep PAF from binding to platelets, can offer some relief. Many clinical studies have demonstrated that taking up to 160 mg of ginkgo extract daily for three to six months is effective, with noticeable improvement after four to six weeks. In one study, 79 patients with restricted blood flow to their legs received either 40 mg of ginkgo extract four times daily or a placebo for 65 weeks. The 39 patients receiving the ginkgo saw a “highly significant” increase in their ability to walk without pain. The same improvement was not experienced by the placebo group.
Chinese researchers performing a controlled study found the EGb improved several measures in coronary artery disease, particularly coronary artery blood flow.
These conclusions do not match all studies, though. A major scientific review from 2009 looked at the collected data from 14 trials with a total of 739 participants and concluded that there is no evidence that ginkgo has a clinically significant benefit for patients with peripheral arterial disease.
Decreased blood circulation or damage to the inner ear can lead to hearing loss, dizziness and loss of balance, which are also closely associated with tinnitus. Some adherents use EGb for these symptoms, and there is mixed evidence that EGb might be effective. One study found EGb to significantly improve dizziness in animals. Adding to the evidence, a 2011 report lays out the case that EGb reduces dizziness-causing damage from ear infections.
In a random, double-blind study of 103 people with chronic tinnitus, participants receiving 2 ml of a ginkgo extract twice a day for 13 months experienced a significant reduction in the severity of ringing.
Ginkgo has received a lot of attention for tinnitus, but studies evaluating ginkgo as a treatment for it have given mixed results. The scientific consensus is that oral ginkgo doesn’t seem to help much. A German study reported, though, that 10 days of EGb infusion, followed by one or more months of oral EGb, appears to be effective and safe in alleviating tinnitus symptoms. In 2011, a German review pointed out that at least eight studies have shown positive effects from EGb in tinnitus, but that efficacy has not been conclusively proven, which may be due to flawed clinical trials. The scientists conclude that EGb is an evidence-based treatment option in tinnitus. Nevertheless, ginkgo is widely used by health-care practitioners, who claim good results.
Whether any treatment is likely to be helpful depends on whether the ringing is constant or intermittent, whether it is in one or both ears, whether the ringing has been present for more than a year and the cause of the ringing. If the ringing has been constant and in both ears for more than a year, the chances for successful treatment are greatly reduced.
Ginkgo has the potential to treat conditions ranging from diabetes to inflammatory skin disease, and research into the extent of its usefulness is continuing. A peek at the scientific literature finds preliminary positive research for diabetic retinopathy, glaucoma and PMS.
Although the raw nuts are toxic in large amounts, ginkgo leaf extracts have produced only minor side effects such as temporary gastrointestinal upset and, rarely, headache and dizziness.
Most of the studies on ginkgo leaf extract used the standardized extract at a therapeutic dosage of 40 mg three times a day, although the rare study has bumped the dose to as high as 960 mg per day, with little in the way of side effects.
Karta Purkh Singh Khalsa is the national president of the American Herbalists Guild and the lead instructor in Nutritional Therapy at Portland Community College in Oregon.
Mashayekh A, Pham DL, Yousem DM, Dizon M, Barker PB, Lin DD. “Effects of Ginkgo biloba on cerebral blood flow assessed by quantitative MR perfusion imaging: a pilot study.” Neuroradiology. 2011 Mar;53(3):185-91.
Wang BS, Wang H, Song YY, Qi H, Rong ZX, Wang BS, Zhang L, Chen HZ. “Effectiveness of standardized ginkgo biloba extract on cognitive symptoms of dementia with a six-month treatment: a bivariate random effect meta-analysis.” Pharmacopsychiatry. 2010 May;43(3):86-91. Epub 2010 Jan 26.
Yancheva S, Ihl R, Nikolova G, Panayotov P, Schlaefke S, Hoerr R; GINDON Study Group. “Ginkgo biloba extract EGb 761(R), donepezil or both combined in the treatment of Alzheimer's disease with neuropsychiatric features: a randomised, double-blind, exploratory trial.” Aging Ment Health. 2009 Mar;13(2):183-90.
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From the Natural Medicines Comprehensive Database: Tinnitus.
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