Ginkgo (Ginkgo biloba) is prepared from leaves of the ginkgo tree (commonly planted in the US for ornamental purposes and botanically unique as it is the only surviving member of its family). Active ingredients are believed to be terpene ginkgolides and flavonoids.
The fruit of the gingko tree, which is quite malodorous, is not used in ginkgo products. Contact with the fruit pulp, which may be present under female ginkgo trees, can cause severe skin inflammation (dermatitis). The raw seeds of the fruit are toxic and can cause seizures and, in large amounts, death. Cooked ginkgo seeds are eaten in Asia and are available in Asian food shops in the US; because the seeds do not contain ginkgolides and flavonoids, they do not have known therapeutic effects.
(See also Overview of Dietary Supplements.)
Ginkgo leaf products are used for minor symptomatic relief of claudication, although exercise and cilostazol may be more effective. Gingko increases the distance that affected people can walk without pain.
Ginkgo has long been used in people with dementia. Gingko has also been used to alleviate memory loss, tinnitus, age-related macular degeneration, and altitude sickness. Gingko may prevent damage to the kidneys caused by the immunosuppressant cyclosporine. Gingko has also been used for acute mountain sickness and as an adjunct to treat type 2 diabetes.
Ginkgo is thought to be a vasoactive agent. Although patients with intermittent claudication may be able to walk longer than placebo-treated patients, this benefit is quite minor according to a 2013 Cochrane review. This review looked at 14 trials with a total of 739 participants, of which 11 trials (477 participants) compared Ginkgo biloba to placebo (1).
Early studies indicated that ginkgo temporarily stabilized mental and social function in people with mild-to-moderate dementia. However, recent large clinical trials showed that ginkgo supplementation (EGb 761) did not delay the development and progression of dementia and Alzheimer disease in older people (2-4). A 2017 overview of 12 systematic reviews (59 randomized controlled trials) of ginkgo with low to moderate evidence reported that, when used at daily doses higher than 200 mg and for ≥ 5 months to treat dementia, cognitive performance, activities of daily living, and clinical global impression improved (5). Further studies are warranted with regard to the clinical use of this supplement for dementia.
A 2013 Cochrane review (6) of 2 studies suggested a potential role for ginkgo in slowing the progression of age-related macular degeneration. A standard ginkgo extract compared to placebo was used in both studies, in which 119 people took the supplement for 6 months. Future large-scale trials for longer periods of time are warranted before claims are supported.
Earlier evidence suggested ginkgo may relieve tinnitus, but a Cochrane review of 4 studies (1543 subjects) shows that it is not helpful when tinnitus is the primary ailment (7). A systematic review and meta-analysis of ginkgo for acute mountain sickness prevention found a benefit trend, but data were insufficient to demonstrate a significant preventive effect (8). Emerging evidence reports benefit of ginkgo in treatment of type 2 diabetes. When combined with metformin, ginkgo significantly decreased fasting glucose and HbA1C (9).
Nicolaï SP, Kruidenier LM, Bendermacher BL, et al:Ginkgo biloba for intermittent claudication. Cochrane Database Syst Rev 6: CD006888, 2013. doi: 10.1002/14651858.CD006888.pub3.
Vellas B, Coley N, Ousset PJ, et al; GuidAge Study Group: Long-term use of standardised Ginkgo biloba extract for the prevention of Alzheimer's disease (GuidAge): a randomised placebo-controlled trial. Lancet Neurol 11(10):851-859, 2012. doi: 10.1016/S1474-4422(12)70206-5.
Snitz BE, O'Meara ES, Carlson MC, et al; Ginkgo Evaluation of Memory (GEM) Study Investigators: Ginkgo biloba for preventing cognitive decline in older adults: a randomized trial. JAMA 302(24):2663-2670, 2009. doi: 10.1001/jama.2009.1913.
DeKosky ST, Williamson JD, Fitzpatrick AL, et al; Ginkgo Evaluation of Memory (GEM) Study Investigators: Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA300(19):2253-2262, 2008. doi: 10.1001/jama.2008.683.
Yuan Q, Wang CW, Shi J, et al: Effects of ginkgo biloba on dementia: an overview of systematic reviews. J Ethnopharmacol 195:1-9, 2017. doi: 10.1016/j.jep.2016.12.005.
Evans JR: Ginkgo biloba extract for age-related macular degeneration. Cochrane Database Syst Rev 31; 1:CD001775, 2013. doi: 10.1002/14651858.CD001775.pub2.
Hilton MP, Zimmermann EF, Hunt WT: Ginkgo biloba for tinnitus. Cochrane Database Syst Rev (3):CD003852, 2013. doi: 10.1002/14651858.CD003852.pub3.
Tsai TY, Wang SH, Lee YK, et al: Ginkgo biloba extract for prevention of acute mountain sickness: a systematic review and meta-analysis of randomised controlled trials. BMJ Open 8(8):e022005, 2018. doi: 10.1136/bmjopen-2018-022005.
Aziz TA, Hussain SA, Mahwi TO, et al. The efficacy and safety of Ginkgo biloba extract as an adjuvant in type 2 diabetes mellitus patients ineffectively managed with metformin: a double-blind, randomized, placebo-controlled trial. Drug Des Devel Ther 12:735-742, 2018. doi: 10.2147/DDDT.S157113.
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Institutes of Health (NIH), National Center for Complementary and Integrative Health: General information on the use of ginkgo as a dietary supplement