Ginkgo Didn't Prevent Alzheimer's

TOULOUSE, FranceLong-term use of standardized Ginkgo biloba extract did not reduce the risk Alzheimer's disease progression compared with placebo in a recent randomized placebo-controlled trial (Lancet Neurol. 2012 Sept 6. DOI:10.1016/S1474-4422(12)70206-5).

However, just because this study didn't find ginkgo prevented Alzheimer's doesn't mean the botanical is worthless, according to Duffy MacKay, N.D., vice president, scientific and regulatory affairs, Council for Responsible Nutrition (CRN). "Responsible marketers of Ginkgo biloba should never market it at a prevention of Alzheimer's," he said.

"The benefits of ginkgo, which are well validated, are its peripheral vascular effects (blood flow to peripheries), such as to help reduce tinnitus and poor circulation. We've been studying Alzheimer's for 20 years, and we haven't found any good treatments yet," MacKay added. "We don't know how to treat it."

Mark Blumenthal, founder and executive director, the American Botanical Council (ABC), also said no responsible herbal supplement company markets ginkgo for Alzheimer's disease because it's illegal to do so and because no previous data shows that. "People are marketing gingko for improvement of short-term memory loss, age-related dementia symptoms and mental possessing in normal, healthy adults. There's strong and compelling evidence for those indications."  He added this study shouldn't adversely affect ginkgo sales, that is, if people understand this study looked at prevention of a disease.

The randomized, parallel-group, double blind, placebo-controlled GuidAge clinical trial, included 2,854 adults aged 70 years or older who reported memory complaints to their primary-care physician. French researchers randomly allocated participants to either two 120-mg  doses of standardized Ginkgo biloba extract (as EGb761, from Schwabe, Williamson & Wyatt, n=1,406) or a placebo (n=1,414). Participants were followed for five years by primary-care physicians and were evaluated by expert memory centers periodically.

EGb 761 is a standardized extract of dried leaves of Ginkgo biloba containing 24-percent ginkgo-flavonol glycosides, 6-percent terpene lactones such as ginkgolides A, B, C, J and bilobalide.

After five years, 61 participants in the ginkgo group had been diagnosed with probable Alzheimer's disease (1.2 cases per 100 person-years) compared with 73 participants in the placebo group (1.4 cases per 100 person-years; P=0.306), but the risk was not proportional over time. Incidence of adverse events was much the same between groups. Seventy-six participants in the ginkgo group died compared with 82 participants in the placebo group (P=0.68). Sixty-five participants in the ginkgo group had a stroke compared with 60 participants in the placebo group (P=0.57). Incidence of other haemorrhagic or cardiovascular events also did not differ between groups.

MacKay noted in a subgroup analysis, researchers found a group that took EGb 761 regularly for four years (not accounting for dropouts) experienced significant positive results. "The incidence of Alzheimer's was reduced by 47 percent compared to placebo. You need to treat these results with caution, but it's a clear trend."

Blumenthal agreed, adding , "If you look at the secondary outcomes in some of the subsets, there were positive trends, but the problem was there wasn't enough people to get to statistically significant trends to report a positive outcome."

Blumenthal added, "People shouldn't throw away their ginkgo. This is not a definitive trial that undermines the legitimacy of  rational, clinically relevant uses of ginkgo."

In a 2006 study, EGb 761 suppressed amyloid-ß (Aß) pathological behaviors and protect against toxicity, preventing synaptic loss and neural degeneration seen in Alzheimers disease (AD). And in 2008, researchers at Johns Hopkins showed daily doses of EGB 761 prevented or reduced brain damage after an induced stroke.

However, this current study is in line with other recent studies that question the herb's effectiveness in treating or preventing Alzheimer's Disease. In 2006, a JAMA study found older adults who used Ginkgo biloba for several years did not see a reduction in cognitive decline compared to adults who received placebo. And in 2008, another JAMA study concluded  the use of Ginkgo biloba was not effective in reducing the rate of dementia or Alzheimers disease among more than 1,500 elderly study participants after several years of use.

Find more information on ginkgo and other brain health nutrients in INSIDER's Cognition Content Library.