(See also Overview of Dietary Supplements.)
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.
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.
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). It is obvious that further studies are warranted with regard to the clinical use of this supplement for dementia.
A 2013 Cochrane review (5) 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 mo. Future large-scale trials for longer periods of time are warranted before claims are supported.
Nicolaï SP, Kruidenier LM, Bendermacher BL, et al.Ginkgo biloba for intermittent claudication. Cochrane Database Syst Rev 6: CD006888, 2013.
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.
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.
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.
Evans JR.Ginkgo biloba extract for age-related macular degeneration. Cochrane Database Syst Rev 31; 1:CD001775, 2013.
von Boetticher A.Ginkgo biloba extract in the treatment of tinnitus: a systematic review. Neuropsychiatr Dis Treat 7:441-447, 2011.
Moraga FA, Flores A, Serra J, et al.Ginkgo biloba decreases acute mountain sickness in people ascending to high altitude at Ollagüe (3696 m) in northern Chile. Wilderness Environ Med18(4):251-257, 2007.
Leadbetter G, Keyes LE, Maakestad KM, et al.Ginkgo biloba does—and does not—prevent acute mountain sickness. Wilderness Environ Med 20(1):66-71, 2009.