Product Review: Gingko
Biloba
Background: Ginkgo biloba has become
a widely used dietary supplement for increasing cognitive functions in elderly
people, delaying the progression of Alzheimer's disease, increasing blood flow
to the legs, treating tinnitus (ringing in the ear) of a circulatory origin, as
well as treating depression and asthma. It is an extract of the leaf of the
Ginkgo biloba tree that is used in dietary supplements.
The Ginkgo biloba extract, or GBE, used in
most clinical trials contains specific types of naturally occurring chemicals:
Flavonol glycosides, of which there are three, are believed to confer
anti-oxidant activity; Terpene lactones, of which there are two categories, may
be responsible for the dilatory effect on blood vessels. Each of these
chemicals is expected to exist in a specific amount in clinical quality GBE,
representing a standard for assessing ginkgo products. Many GBE products now
claim to be "standardized" or manufactured to contain specific total amounts of
flavonol glycosides and/or total terpene lactones.
Currently, there is no government
monitoring of the manufacture of Ginkgo biloba or other dietary supplements in
the U.S. There have been numerous independent reports of dietary supplements
not containing their stated ingredients. In order to identify products
containing GBE of quality most similar to that used in clinical trials,
ConsumerLab.com purchased and tested leading Ginkgo biloba products in the
U.S.
Testing &
Results: ConsumerLab.com purchased thirty leading brands of
Ginkgo biloba during August 1999. These products were then tested to determine
whether or not they possessed proper amounts of appropriate plant
chemicals.
Nearly one quarter
of the thirty brands tested did not have the expected levels of chemical
marker compounds for GBE.
Among these, all had less than adequate
levels of one of one or more terpene lactones, and three also lacked adequate
levels of one or more flavone glycosides. Even though they did not pass the
testing, all bore labels claiming standardization for total flavone glycosides
and most also indicated being standardized for total terpene lactones. Some of
these labels were actually correct for total amounts of compounds but the
products did not meet the standards for one or more specific
compounds.
Examples of some of the products
that passed review are:
(Listed in order of Product Name,
Labeled Concentration of Ginkgo Biloba Extract Per Pill,
and Manufacturer and/or Distributor) Ginkgo Biloba and
DHA, 53.3 mg/softgel* Nutrilite (Access Business Group International
LLC (formerly Amway) Ginkgolidin, Ginkgo Biloba Standardized
Extract, 40 mg/ capsule* PhytoPharmica Enzymatic
Therapy, Ginkgo Biloba 24%, 40 mg/capsule* Enzymatic
Therapy NOW Ginkgo Biloba 24% Standard Extract, 60
mg/capsule* NOW Foods
|