Don't Forget the Gingko: Just Make Sure It's the Right One

In the search for ways to effectively treat people with age-related memory loss and Alzheimer’s disease, researchers have identified several ingredients that may play a role in enhancing memory and cognitive function. Among the most promising approaches are ginkgo, huperzine A and acetyl-L-carnitine. These three supplements were the focus of recent testing by ConsumerLab (CL), a consumer "watchdog" of sorts that provides independent evaluations of dietary supplements, as well as other products that affect health and nutrition, for the quality of their ingredients and other relevant parameters, in the absence of government standards. While acetyl-L-carnitine passed CL testing with flying colors, few ginkgo and huperzine supplements met quality standards and adulteration is suspected in some cases.  

Ginkgo biloba leaf extract (GBE) is widely used in delaying the progression of Alzheimer’s disease and for increasing cognitive functions in the elderly, as well as for reducing pain while walking in intermittent claudication, decreasing the symptoms of vertigo, reducing painful attacks of Reynaud’s syndrome, treating tension glaucoma and symptoms of premenstrual syndrome. GBE used in most clinical trials contains two major groups of phytochemicals; flavonol glycosides, which are believed to confer antioxidant activity, and terpene lactones that may be responsible for a dilatory effect on blood vessels. Bilobalide, one of the terpene lactones, may also increase brain activity by affecting GABA receptors and enhancing the excitability of neurons in the hippocampus of the brain, which is associated with learning and memory.

In order to reduce their costs, some manufacturers or their ingredient suppliers provide less ginkgo than claimed or use material that has been adulterated or “spiked” with one or more compounds that can trick simple chemical tests. This makes a product with little or no real ginkgo appear to be the real thing. “Ginkgo extract is a moderately expensive ingredient. Some companies put less of it in their products than they claim or use ingredient that has been adulterated with inexpensive material that can fool-non specific tests,” said Dr. William Obermeyer,  CL’s Vice President for Research and a former FDA Natural Products Chemist, who has been monitoring problems with ginkgo for several years. 

However, the highly specific test methods used by CL reveal this type of adulteration by showing the ratios of specific flavonal glycosides and comparing them to established standards. Among the seven ginkgo products selected for CL’s latest review, only two passed the tests. Two products appeared to contain adulterated material and two others contained less ginkgo than claimed on their labels, one of which was contaminated with lead and also failed to break apart properly. Another product failed to identify the part of the ginkgo plant used, a FDA labeling requirement.

In 1999, CL’s review of ginkgo products found that nearly one-fourth of the thirty brands tested did not have the expected levels of chemical marker compounds, despite claims to have been “standardized.” Even worse, testing in 2003 found that seven of nine ginkgo products lacked adequate levels of certain marker compounds, and six products failed testing for the same reason in 2005. CL’s past tests have also detected lead contamination in some ginkgo products made with leaf powder.

Huperzine A is a chemical purified from the leaves of the Chinese toothed club moss, or synthetically manufactured. It has been shown, in limited studies, to improve memory, thinking and behavioral function in people with Alzheimer’s disease, multi-infarct dementia and senile dementia. Scientists believe that huperzine A works by increasing the level of the neurotransmitter acetylcholine by clocking its breakdown. It may also protect neurons from cell death caused by toxic levels of glutamate and protect against some of the effects of chemical nerve agents used in warfare.

Huperzine A is also a relatively expensive ingredient, creating an economic incentive for making a product with less than the labeled amount. Among the huperzine products tested by CL, two passed testing while a third provided only 14 percent of its claimed amount of the ingredient. Tests by CL in 2005 detected no huperzine in one product. Lead contamination is also possible with huperzine A, as CL found in 2003 testing.

Acetyl-L-carnitine is a form of carnitine, a non-essential amino acid that can be synthesized in the body from lysine and methionine and is found in red meats and dairy products. Acetyl-L-carnitine may improve memory and cognition in older people with age-related memory problems, but has had mixed reviews in its benefits for Alzheimer’s disease and other forms of dementia. It seems to improve symptoms of diabetic neuropathy and neuropathy associated with antiretroviral drug therapy used by people with HIV infection and may also reduce pain and improve mental health in people with fibromyalgia. A combination of acetyl-L-carnitine and propionyl-L-carnitine seems to help symptoms of androgen decline in older men, improving sexual dysfunction, depression and fatigue. It may also improve memory in chronic alcoholics and increase sperm motility in men with infertility. All five acetyl-L-carnitine supplements passed CL’s testing.

The brands covered in CL’s new report, "Product Review of Supplements for Memory and Cognition Enhancement," include BioSynergy, Bluebonnet, Cognitive Nutrition, Freeda, Ginkgo-Go!, Ginkoba, Life Enhancements, Nature’s Valley, Nutricology, Olympian Labs, Puritan’s Pride, Solaray, Swanson, Total Nutrition, Universal Naturals, Vitamin Shoppe, and Vitamin World. The complete report, as well as extensive information about how to buy and use these supplements and their potential side effects, is available here.