Myths about Ginkgo biloba

More legends have formed around ginkgo biloba than around many medicines. It is called a "memory pill", a remedy for brain aging, a natural "blood thinner" and even a secret weapon of athletes. The editorial team has checked the most widespread claims against the results of clinical studies and systematic reviews.

Myths 1–2: ginkgo improves memory and prevents dementia

Myth 1: "Ginkgo improves memory in healthy people".This is probably the most widespread belief. However, in the randomized study by Solomon and colleagues, published in JAMA in 2002, six weeks of taking 120 mg of extract per day by healthy people over 60 years old gave no advantages in tests of memory, attention or speech compared with placebo.

Short-term studies with young people recorded individual improvements in attention after single doses, but these effects were inconsistent and small. It is incorrect to speak of a stable "memory improvement" on the basis of such data.

Myth 2: "Regular ginkgo intake protects against dementia".This hypothesis was tested by the two largest trials. In the American GEM, more than 3000 people aged 75 and over took 240 mg per day for an average of about six years — the incidence of dementia and Alzheimer's disease did not decrease. An additional analysis by Snitz and colleagues showed that ginkgo did not slow cognitive decline either.

The European GuidAge study with five years of intake gave a similar result. The Cochrane review also characterizes the evidence of efficacy in cognitive impairment as inconsistent. Thus, dementia prevention is the most refuted of ginkgo's "effects".

Myth 3: natural means safe

Plant origin is often perceived as a guarantee of safety. However, ginkgo contains biologically active substances that affect platelets, liver enzymes and the nervous system. That is precisely why it has contraindications and interactions with medications.

Clinical cases of bleeding have been described in people who took ginkgo, mostly together with anticoagulants or aspirin. Ginkgo seeds contain ginkgotoxin, capable of causing seizures. Raw fruit causes contact dermatitis due to ginkgolic acids.

Toxicological studies by the US National Toxicology Program in rodents revealed tumors of the liver and thyroid gland at very high doses, and the International Agency for Research on Cancer classified ginkgo extract in group 2B ("possibly carcinogenic to humans").

This does not mean that ginkgo is dangerous for everyone, but it does mean that it should be treated as a pharmacologically active substance: with regard to indications, doses and contraindications.

Myths 4–5: more blood in the muscles and protection from altitude

Myth 4: "Ginkgo enhances circulation in the muscles and increases endurance".Ginkgo's vascular effects concern mainly microcirculation and are best studied in patients with disorders of it. Even in people with intermittent claudication, where blood flow in the legs is substantially limited, the Cochrane review found no clinically significant increase in walking distance.

Isolated studies in physically active people reported changes in aerobic indicators, but they are small and require reproduction. The promises of "pumping" and "explosive endurance" from ginkgo in pre-workout complexes have no evidence base.

Myth 5: "Ginkgo protects against mountain sickness".This idea relied on several small early studies. However, in the randomized PHAIT trial among trekkers in the Himalayas, ginkgo did not differ from placebo, whereas acetazolamide was effective.

The clinical guidelines of the Wilderness Medical Society do not advise using ginkgo for the prevention of altitude sickness. Climbers and athletes who train in the mountains should rely on gradual acclimatization and proven methods discussed with a doctor.

Myths 6–7: tinnitus and "the more the better"

Myth 6: "Ginkgo cures tinnitus".Ginkgo has been offered for tinnitus for decades, explaining this by improved blood supply to the inner ear. The Cochrane review by Hilton and colleagues in 2013 found no evidence of ginkgo's efficacy in patients for whom tinnitus was the main complaint.

Myth 7: "The higher the dose, the stronger the effect".Doses in studies were usually 120–240 mg of standardized extract per day. There is no evidence that higher doses provide greater benefit, while the risk of side effects and interactions increases.

Another related myth is that ginkgo's effect is felt immediately. Even for cognitive indications, official recommendations envisage at least eight weeks of intake before assessment, and the absence of changes after three months is a reason to reconsider its advisability.

Myth 8: tea and leaf powder are the same as the extract

When a person hears that "ginkgo was studied in clinical trials", they often think that any product with ginkgo will have the same properties. In reality, almost all significant studies were conducted with the standardized extract, in which the content of flavonol glycosides and terpene lactones is strictly standardized.

Ginkgo leaf tea contains a negligible amount of terpene lactones, and leaf powder is an unpurified mixture in which ginkgolic acids are present. It is incorrect to transfer the results of clinical studies to them, neither regarding benefit nor safety.

The situation is even worse with the seeds, which are sometimes sold as a "superfood": they contain ginkgotoxin, and consuming them in large quantities can cause poisoning.

For the consumer, the conclusion is simple: if you are going to take ginkgo, then a standardized leaf extract with a known composition and from a trusted manufacturer.

Editorial conclusions

Most popular notions about ginkgo biloba do not withstand testing by large studies: the extract does not prevent dementia, does not improve memory in healthy people, does not protect against mountain sickness and does not cure tinnitus.

At the same time, ginkgo is not a "dummy": it has pharmacological activity, and therefore real risks as well, especially for people who take medications that affect blood clotting.

A critical attitude toward marketing promises and orientation toward data from randomized studies are the best protection against unnecessary expenses and undesirable effects.

We also advise reading "The benefits of Ginkgo biloba for athletes: the evidence base", "Who should not take Ginkgo biloba" and "Bacopa monnieri: what it is and how it works".

References

1. Solomon PR, Adams F, Silver A, Zimmer J, DeVeaux R. Ginkgo for memory enhancement: a randomized controlled trial. JAMA. 2002;288(7):835–840.
2. DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA. 2008;300(19):2253–2262.
3. Snitz BE, O'Meara ES, Carlson MC, et al. Ginkgo biloba for preventing cognitive decline in older adults: a randomized trial. JAMA. 2009;302(24):2663–2670.
4. Vellas B, Coley N, Ousset PJ, et al. Long-term use of standardised Ginkgo biloba extract for the prevention of Alzheimer's disease (GuidAge): a randomised placebo-controlled trial. Lancet Neurol. 2012;11(10):851–859.
5. Birks J, Grimley Evans J. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database Syst Rev. 2009;(1):CD003120.
6. Gertsch JH, Basnyat B, Johnson EW, Onopa J, Holck PS. Randomised, double blind, placebo controlled comparison of ginkgo biloba and acetazolamide for prevention of acute mountain sickness among Himalayan trekkers: the prevention of high altitude illness trial (PHAIT). BMJ. 2004;328(7443):797.
7. Hilton MP, Zimmermann EF, Hunt WT. Ginkgo biloba for tinnitus. Cochrane Database Syst Rev. 2013;(3):CD003852.
8. Bent S, Goldberg H, Padula A, Avins AL. Spontaneous bleeding associated with Ginkgo biloba: a case report and systematic review of the literature. J Gen Intern Med. 2005;20(7):657–661.