What you need to know about ginkgo biloba

According to the National Institute of Health, Americans spend more than $33 billion dollars on complementary and alternative medicine (CAM) annually, accounting for more than 10 percent of out-of-pocket purchases.  

What you need to know about ginkgo biloba

CAM is comprised of a diverse set of treatments and supplements, such as vitamins, chiropractors, acupuncture and herbal therapies. While marketing campaigns actively promote daily vitamins as the key to vitality and improved wellness, they comprise only a modest proportion of CAM sales. The majority of spending, more than $14 billion dollars, has been directed towards non-vitamin, non-mineral, herbal products. This is equivalent to one-third of the personal spending on prescription drugs.

Consumers are actively seeking alternative treatments for a variety of ailments, from arthritis to the common cold. Annual sales have been rising in recent years despite a delicate economy.  People are trying to avoid doctor visits by pursuing preventative therapies, following claims of improved immunity and memory to the cash register.  In 2009, more than $250 million dollars were spent on ginkgo biloba alone, one of the top 10 purchased natural product. Ginkgo is one of the most widely used and studied herbal remedies in the world.

Ginkgo biloba has been used medicinally for more than 5,000 years. Originally extracts were used to treat pulmonary diseases, such as bronchitis and asthma. More recently, however, ginkgo has been favored to prevent memory loss anddementia.  It is believed that flavonoids within the plant are responsible for its proposed medicinal effects, with over 40 different flavonoids have been isolated from leaves from the ginkgo tree. Flavonoids are compounds found ubiquitously in plants having varying antioxidant properties.  In animal models these compounds appear to alter neuro-communications and protection against neurologic changes associated with aging, however findings in humans are conflicting. 

Despite being the subject of more than 400 clinical investigations, the efficacy of ginkgo in humans is still undecided.

While many of these trials were small, preventing generalizability, a few large randomized controlled trials have been recently published, which question the utility of ginkgo. In 2009, the results were released of a large randomized controlled trial designed to evaluate the effectiveness of ginkgo biloba versus placebo in reducing the incidence of dementia and Alzheimer disease in elderly individuals.  The authors followed approximately 3,000 volunteers over the age of 75 for a median of 6 years. Half of the participants were assigned to take ginkgo twice a day and the other half took a placebo. At the end of the trial, no significant difference was noted between those in the ginkgo group and those consuming the placebo.  Overall, the study failed to find any decrease in the incidence or rate of progression of dementia or Alzheimer disease associated with daily ginkgo supplements.

Others have found similarly disappointing results regarding ginkgo’s ability to enhance memory. In a randomized double-blinded, placebo-controlled study, researchers investigated the effect of daily ginkgo on memory, attention, and learning in 330 volunteers older than 60. After following participants for 6 weeks, the authors of the study failed to find any difference between those taking the real supplement and those in the placebo group. These findings suggest that when taken following the manufacturer’s instructions, ginkgo fails to provide cognitive benefits

Proponents argue that these studies were too short to demonstrate the proposed benefit of ginkgo, particularly given the long natural history of dementia. Additionally, some studies have demonstrated slight benefits with ginkgo. One study, which looked at the effectiveness of gingko in decreasing Alzheimer patients cognitive decline, found that ginkgo was comparable to donepezil, a commonly used medication for Alzheimer disease.

While the cost associated with herbal supplements represents just a fraction of overall health care spending, it comprises a significant proportion of out-of-pocket expenses. As such, the utility of supplements, like ginkgo, should be evaluated thoroughly before widespread use.  Although the majority of studies are inconclusive regarding the benefits of ginkgo, they do, however, demonstrate that ginkgo is safe, with few participants experiencing adverse events.  Ginkgo is known to interfere with normal blood clotting. Thus, in patients on blood thinners (Indocin, Coumadin, Plavix,  Lovenox, and Ticlid), ginkgo should be used with caution. Additionally, prior to starting any new supplement it is essential to discuss it with a physician.  

The continued popularity of ginkgo despite very limited evidence to support it highlights a general trend in consumer spending. Studies have shown that purchasing of supplements is unaffected by the publication of negative studies. This pattern has been seen with St. John’s Wort, Echinacea, saw palmetto and glucosamine. As a physician, I advocate for evidence base medicine, making recommendations on the basis of documented utility and advise that my patients follow the same principle.