1. No category

Variation in Concentration and Labeling of
Ginger Root Dietary Supplements
Harvey A. Schwertner,
PhD,
Deborah C. Rios, and Joshua E. Pascoe
OBJECTIVE: Ginger root dietary supplements are often
used to alleviate symptoms of nausea and vomiting
associated with pregnancy. In this study, we determined
the variation in 6-gingerol, 6-shogaol, 8-gingerol, and
10-gingerol concentrations and labeling of different
brands of ginger root dietary supplements.
METHODS: Ten different ginger root dietary supplements
were purchased randomly at local pharmacies and health
food stores. The 6-gingerol, 6-shogaol, 8-gingerol, and
10-gingerol concentrations of the dietary supplements were
determined by high-performance liquid-chromatography.
In addition, we examined the container labeling for the
amount of ginger root powder or extract in each capsule,
the serving size, ingredients, expiration date, lot number,
standardization procedure, and suggested use.
RESULTS: The 6-gingerol concentration of the ginger
powder dietary supplements ranged from 0.0 to 9.43
mg/g, (mean ⴞ standard deviation, 2.56 ⴞ 2.95 mg/g),
6-shogaol ranged from 0.16 to 2.18 mg/g (1.27 ⴞ 0.58),
8-gingerol ranged from 0.00 to 1.1 mg/g (0.47 ⴞ 0.34),
and 10-gingerol ranged from 0.00 to 1.40 mg/g (0.36 ⴞ
0.51). The amounts of 6-gingerol, 6-shogaol, 8-gingerol,
and 10-gingerol in the ginger root dietary supplements
varied widely on both a milligram per gram basis and on
a milligram per capsule basis. Likewise, the suggested
ginger serving sizes varied from 250 mg to 4.77 g per day.
CONCLUSION: The results of this study indicate that
there is a wide variation in the gingerol composition and
in the suggested serving sizes of ginger root powder from
different manufacturers.
(Obstet Gynecol 2006;107:1337–43)
LEVEL OF EVIDENCE: II-3
From Clinical Research, Wilford Hall Medical Center, Lackland AFB, Texas;
Department of Science, Castle Hills First Baptist School, San Antonio, Texas;
and Department of Chemistry, United States Air Force Academy, Colorado.
The views expressed in this article are those of the authors and do not reflect the
official policy of the Department of Defense or other departments of the United
States Government.
Corresponding author: Dr. Harvey A. Schwertner, 2200 Bergquist Drive,
Lackland AFB, Texas; e-mail: [email protected].
© 2006 by The American College of Obstetricians and Gynecologists. Published
by Lippincott Williams & Wilkins.
ISSN: 0029-7844/06
VOL. 107, NO. 6, JUNE 2006
G
inger (Zingiber officinale Roscoe) is widely used as
a dietary supplement as well as a spice and
flavoring agent in foods and beverages. Ginger has
been used to treat a variety of medical conditions,
including nausea and motion sickness.1– 8 Ginger dietary supplements have recently been shown to be
effective in relieving the symptoms of nausea and
vomiting associated with pregnancy.2–7 A recent comprehensive review of 6 double-blind, randomized
controlled trials has shown that ginger may be effective in treating pregnancy-related nausea and vomiting.7 Four of the clinical trials showed ginger to be
more effective in relieving nausea than the placebo,
and two showed that ginger was as effective as the
vitamin B6 reference drug.2–7 There were no significant adverse effects on pregnancy outcomes in any of
the 6 clinical trials.
The results with ginger have not always been
consistent, even in studies involving pregnancy-related nausea.6 – 8 Meta-analysis, for example, failed to
show that ginger is effective in the treating postoperative nausea, motion sickness, or nausea of other
etiology.8 The factors contributing to the variability in
response to ginger in the clinical studies are not
known. Such differences, however, could be due to
differences in the doses administered, the duration of
the treatment, the quality of the ginger products used,
or to differences in the composition of the ginger
powders and ginger extracts used in the studies. The
composition of the ginger constituents have not been
analyzed in any of the clinical studies.2– 8 Standardization of the ginger composition and doses used in
clinical studies is needed if the clinical studies are to
be reproduced and if the efficacies of ginger and its
components are to be established.
6-Gingerol, 8-gingerol, and 10-gingerol have
been identified as the principal pungent components
of ginger powder.9 –11 6-Gingerol and the other pungent compounds present in ginger powder have been
shown to have analgesic, antipyretic, and cardiotonic
effects12 and to inhibit spontaneous motor activities
OBSTETRICS & GYNECOLOGY
1337
and prostaglandin biosynthesis.13 In addition, 6-gingerol has been shown to have antioxidant and antiinflammatory properties,13,14 to suppress cytokine formation,14,15 and to promote angiogenesis.15 6-Shogaol,
a dehydration product of 6-gingerol, is also found in
ginger powder, but not in fresh ginger powder.10
6-Shogaol appears to be formed from 6-gingerol
during thermal processing or long-term storage and
has no known pharmacological properties.10,11 The
purpose of this study was to determine the variability
in the 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol concentrations, the recommended serving sizes,
and the labeling of 10 different brands of ginger root
dietary supplements.
MATERIALS AND METHODS
6-Gingerol, 6-shogaol, 8-gingerol, and 10-gingerol
were obtained from ChromaDex Inc (Santa Ana,
CA). 6-Gingerol was also obtained from Aldrich
Chemical Company (Milwaukee, WI) and Wako
Pure Chemical (Osaka, Japan). USP Reference Standard Powdered Ginger (Cat. No. 29150-4) was obtained from U.S. Pharmacopeia (USP, Rockville,
MD). High-performance liquid chromatography
(HPLC)-grade methanol and ethyl acetate were obtained from Fisher Scientific (Fair Lawn, NJ). Ten
different ginger root dietary supplements were obtained from health food stores and pharmacies in San
Antonio, Texas. The Wilford Hall Medical Center
Institutional Review Board approved the study protocol.
Ten capsules containing ginger powder were
opened, placed in a beaker, and mixed to insure that
a homogenous sample was obtained. Two hundred
fifty milligrams of each sample were weighed out in
duplicate and placed in separate 16 ⫻ 125 mm
round-bottom glass centrifuge tubes. Ten milliliters of
ethyl acetate were then added with a repipet to each
of the tubes. The tubes were capped, mixed briefly,
and allowed to sit overnight at room temperature.
The ginger samples were extracted on an Eberbach
shaker at slow speed for about 30 minutes. The
samples were centrifuged at 2,500 ⫾ 100 rpm (rotor
216, IEC CentraGP8R, Needham Heights, MA) for
20 minutes at 25 ⫾ 4°C. The top organic layer was
transferred with a Pasteur pipet to separate 16 ⫻ 125
mm glass conical centrifuge tubes, and the extracts
were evaporated under nitrogen at 45 ⫾ 2°C in a
Zymark Turbovap (Caliper Life Sciences, Hopkinton,
MA). The ginger dietary supplements were then
re-extracted with 10.0 mL of ethyl acetate, and the
extracts were transferred to the tubes containing the
first extract. After evaporating the ethyl acetate, each
1338
Schwertner et al
Ginger Root Dietary Supplements
extract was reconstituted in 2.0 mL of the mobile
phase (methanol-water 65:35, vol/vol). The extracts
were vortex mixed for about 25 seconds and centrifuged at 2,000 ⫾ 50 rpm for 20 minutes to further
remove any particulate material. The extracts were
then transferred with a Pasteur pipet to 70-␮L injection vials and capped.
6-Gingerol, 6-shogaol, 8-gingerol, and 10-gingerol used for preparing the standards were dried
over silica gel for at least 3 hours under vacuum and
then weighed. Approximately 10.0 mg of 6-gingerol,
6-shogaol, 8-gingerol, and 10-gingerol were weighed
and transferred to separate 16 ⫻ 125 mm screwcapped glass centrifuge tubes. Sufficient HPLC-grade
methanol was added to each standard to produce a
stock standard of 1.0 mg/mL. Standards containing
500.0 ␮g/mL of 6-gingerol, 6-shogaol, 8-gingerol, and
10-gingerol were prepared by transferring 5.0 mL
(5,000 ␮g) of each of the stock standards to a 16 ⫻ 125
mm conical centrifuge tube, evaporating the methanol at 45 ⫾ 2°C, and reconstituting in 10.0 mL of
methanol-water (65:35, vol/vol). Serial dilutions of
the 500.0 ␮g/mL standard were made to produce the
250.0, 100.0, 50.0, 25.0, and 10.0 ␮g/mL working
standards. All ginger standards were capped and
stored at 4 ⫾ 4°C until used.
The ginger extracts were analyzed on a HPLC
system consisting of a Waters 600E Controller, 717
Autosampler, 996 Photodiode Array Detector (PDA),
and a Millennium 2010 Chromatography Manager
(Waters, Milford, MA). Chromatographic analysis
was performed on a 3.9 ⫻ 150 mm Waters Symmetry
C-8 reversed-phase column (Cat. No. WATO 54235)
with methanol-water (65:35, vol/vol) as the mobile
phase. The HPLC operating parameters were as
follows: injection volume 25 ␮L, column flow rate 1.0
mL/minute, chromatographic run time 48.0 minutes,
and PDA spectra recording 282 nm.
RESULTS
The ginger dietary supplements that were analyzed
are listed in Table 1. Information is provided on the
brand name, manufacturer, formulation, serving size,
lot number, expiration date, ingredients present, the
standardization procedures used, and the intended
use. Most of the supplements were formulated in
gelatin capsules. Seven of the 8 ginger root powder
dietary supplements stated that the capsules contained either 530 or 550 mg of ginger root powder per
capsule, one contained 250 mg of ginger root powder,
one was obtained in bulk form from a self-serve herbs
bin (Sun Harvest Farms), and one contained a ginger
root extract (Enzymatic Therapy) (Table 1).
OBSTETRICS & GYNECOLOGY
VOL. 107, NO. 6, JUNE 2006
Schwertner et al
Ginger Root Dietary Supplements
1339
550 mg/capsule
1.1 g/serving
550 mg/capsule
1.1 g
550 mg/capsules
1 capsule twice
daily
550 mg/capsule
1.1 g/serving
Solaray Ginger Root Dietary
Supplement
Now Ginger Root Herbal
Dietary Supplement
Rexall Natural Whole Herb
Ginger Root
550 mg/capsule
GNC Ginger Root Herbal
Supplement
Sun Harvest Farms
29394
No expiration date
PB11534
Feb 08
061109
Mar 06
399104 2229
Oct 04
210287
Jul 07
202232396
May 07
235853
Aug 05
F
Jan 07
1027221
No expiration date
Lot Number
Expiration Date
General Nutrition Corp, Pittsburgh, 0484AF1977
PA 15222, USA
Jan 09
No expiration date
Enzymatic Therapy, Green Bay,
Wisconsin 54311 USA
Nature’s Resource Products,
Mission Hills, California 913469606 USA
Nutraceutical Corp. for Solaray,
Park City, Utah 84060 USA
Now Foods, Bloomingdale, Illinois
60108 USA
Rexall, Inc, Boca Raton, Florida
33487 USA
Nature’s Herbs, a Twinlab
Division, American Fork, Utah
84003 USA
U.S. Pharmacopeia, Rockville,
Maryland 20852 USA
Natural Organics Laboratory, Inc,
Amityville, New York 11701
USA
Nature’s Way Products, Inc,
Springville, Utah 84663 USA
Manufacturer, City, Country
Gelatin
Gelatin capsule,
canola oil,
beeswax, lecithin
Gelatin, vegetable
magnesium
stearate, silica
Gelatin, water,
silicon dioxide
None listed
Gelatin, purified
water MCT,
vitamin E,
rosemary
Gelatin capsule
Gelatin, silica,
dicalcium
phosphate, water
Gelatin capsule
Other Ingredients
USP, United States Pharmacopeia; MCT, medium-chain triglyceride; TLC, thin-layer chromatography; GNC, General Nutrition Corporation.
Bulk self-serve herb
100 mg ginger root
extract, 1 capsule
3 times/day
Enzymatic Therapy Gingerall
Nature’s Resource Herbal
Supplement
530 mg/capsule
3 capsules,
3 times/day
550 mg/capsule
2 capsules (1.1 g),
4 times/day
250 mg/capsule
1 capsule/day
Powder
Formulation/Serving
Size
Nature’s Herbs Ginger Root
Herbal Supplement
USP Reference Standard
Powdered Ginger
Nature’s Plus Ginger
Standardized Botanical
Supplement
Nature’s Way Ginger Root
Dietary Supplement
Name of Herbal
Supplement
Promotes digestive health.
Herbs are screened and
finely milled.
Material verified by TLC,
USP 2091 for weight,
USP 2040 for
disintegration. Helps
maintain a calm
stomach.
Containing world’s
strongest, standardized
extract; extract
standardized to contain
20% pungent
compounds calculated
as 6-gingerol and 6shogaol.
Supports digestive health.
Guaranteed to contain
1.3% essential oils to
ease stomach discomfort
associated with travel
and stimulate digestion.
Standardized to contain
4% (10 mg) volatile oils.
Standardization/Use
Table 1. Name of Dietary Supplement, Formulation, Serving Size, Manufacturer, Lot Number, Expiration Date, Other Ingredients,
Standardization, and Suggested Use
The serving sizes of the ginger dietary supplements varied widely from brand to brand (Table 1).
The serving size of 4 brands was 1.1 g per serving.
The other serving sizes ranged from a low of 250 mg
(Nature’s Plus Ginger, 1 capsule/day) to a high of
4.77 g per day (Nature’s Herbs Ginger Root Herbal
Supplement, 1.59 g 3 times per day). Only 5 manufacturers made recommendations as to the number of
capsules that should be taken per day. Nature’s Plus
recommended 1 capsule per day (0.25 g), Nature’s
Way recommended 8 capsules per day (4.4 g), Nature’s Herbs recommended 9 capsules per day (4.77
g), Rexall recommended 2 capsules per day (1.1 g),
and Enzymatic Therapy recommended 3 capsules per
day (0.3 g extract).
Lot numbers were listed on all of the container
labels, expiration dates on 7 of 10 brands, and ingredients on 8 of 10 brands. Only 3 of the brands
presented information on how they standardized the
composition of their products. Nature’s Plus Ginger
Standardized Botanical Supplement was standardized
to contain 10 mg of volatile oils, Nature’s Way to
contain 1.3% essential oils, and Enzymatic Therapy
Gingerall to contain 20.0 mg of 6-gingerol and 6-shogaol. The bulk ginger powder that was obtained from
Sun Harvest did not provide any information on dose,
lot number, ingredients, expiration date, standardization, or suggested use. It did state that the ginger
powder did not contain sulfites.
In this study, we developed a new extraction
procedure and a HPLC procedure for the quantitative
analysis of 6-, 8-, and 10-gingerol and 6-shogaol in
ginger dietary supplements and in other products
containing ginger. The recoveries for 6-gingerol,
6-shogaol, 8-gingerol, and 10-gingerol from ginger
powder with a single ethyl acetate extraction were
94.7, 93.6, 94.9, and 97.1%, respectively; with 2
extractions, the recoveries were 99%. The standard
curves for 6-gingerol, 6-shogaol, 8-gingerol, and 10gingerol were linear from 10.0 to 1,000.0 ␮g/mL
(correlation coefficient ⱖ 0.9996). If the concentrations of 6-gingerol, 6-shogaol, 8-gingerol, and 10gingerol in the dietary supplements were less than
50.0 ␮g/mL, standard curves were prepared over a
concentration range of 10.0 –50.0 ␮g/mL. The withinday coefficients of variation for 6-gingerol, 6-shogaol,
8-gingerol, and 10-gingerol at 50␮g/mL were 2.54%,
2.38%, 2.55%, and 2.31%, respectively; at 100 ␮g/mL,
they were 1.92%, 1.81%, 1.87%, and 1.74%, respectively.
The mean concentrations of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol in the ginger dietary
supplements are shown in Table 2. The concentrations are the means of duplicate analyses of each
ginger dietary supplement and are expressed on a
milligram-per-gram basis and/or a milligram-per-capsule basis. The 6-gingerol concentration in the different ginger dietary supplements was higher than that of
Table 2. 6-Gingerol, 6-Shogaol, 8-Gingerol, and 10-Gingerol Composition of Ginger Dietary
Supplements and USP Ginger Powder*
Ginger root powder dietary supplements
Nature’s Plus
Nature’s Way
Nature’s Herbs
Solaray
Now
Rexall
Nature’s Resource
GNC
Sun Harvest Farms
Mean
Standard deviation
CV (%)
Ginger root extract dietary supplements
Enzymatic Therapy†
USP Ginger Powder
6-Gingerol
[mg/g (mg/cap)]
6-Shogaol
[mg/g (mg/cap)]
8-Gingerol
[mg/g (mg/cap)]
10-Gingerol
[mg/g (mg/cap)]
0
(0)
1.17 (0.64)
1.17 (0.62)
1.24 (0.68)
1.25 (0.69)
1.63 (0.90)
1.88 (1.03)
5.24 (2.88)
9.43
2.56 (0.93)
2.95 (0.84)
115.2 (90.3)
0.16 (0.04)
1.18 (0.65)
1.66 (0.88)
1.17 (0.64)
1.57 (0.86)
1.11 (0.61)
0.77 (0.42)
1.64 (0.90)
2.18
1.27 (0.63)
0.58 (0.29)
45.7 (46.0)
0
(0)
0.51 (0.28)
0.52 (0.29)
0.51 (0.28)
0.74 (0.41)
0.39 (0.21)
0.49 (0.27)
1.1 (0.61)
0
0.47 (0.29)
0.34 (0.17)
72.3 (58.6)
0
(0)
0
(0)
0
(0)
0
(0)
0.36 (0.20)
0.66 (0.36)
0.83 (0.46)
1.4 (0.77)
0
0.36 (0.22)
0.51 (0.29)
141.7 (131.8)
(4.78)
3.25
(10.23)
1.27
(2.43)
1.51
(1.62)
1.34
cap, capsule; USP, United States Pharmacopeia; GNC, General Nutrition Corporation; CV, coefficient of variation.
* Nature’s Plus, Nature’s Way, Nature’s Herb, Solaray, Now, Enzymatic Therapy, and USP Ginger Powder were analyzed on June 8, 2005;
Rexall, Nature’s Resources, and GNC on June 14, 2005, and Sun Harvest Farms on January 24, 2002.
†
6-Gingerol, 6-shogaol, 8-gingerol, and 10-gingerol concentrations of Enzymatic Therapy Gingerall capsules are on a milligram/capsule
basis.
1340
Schwertner et al
Ginger Root Dietary Supplements
OBSTETRICS & GYNECOLOGY
the 8-gingerol or 10-gingerol concentration, but not
always higher than that of 6-shogaol. Across brands,
the 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol
concentrations varied widely. For example, the Nature’s Plus ginger dietary supplement contained no
6-gingerol, 8-gingerol, or 10-gingerol, whereas the
6-gingerol concentration in the bulk ginger powder
from Sun Harvest was 9.43 mg/g. One gram of ginger
powder contained on average 2.56 ⫾ 2.95, 1.27 ⫾
0.58, 0.47 ⫾ 0.34, and 0.36 ⫾ 0.51 mg (mean ⫾ SD)
of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol,
respectively (Table 2). On a weight basis, 6-gingerol
made up about 0.256% of the ginger powder, whereas
the 6-shogaol, 8-gingerol, and 10-gingerol made up
0.127%, 0.047%, and 0.036%, respectively.
The total amount of 6-gingerol in the recommended daily serving for each dietary supplement
was calculated to determine if the total daily 6-gingerol amount might be more uniform across brands
on this basis. Only 5 brands listed a daily dose. The
amount of 6-gingerol in the recommended daily
serving was calculated by multiplying the 6-gingerol
concentration per capsule by the number of capsules
to be taken per day as listed in Tables 1 and 2. Based
on the recommended daily serving size, the total
amounts of 6-gingerol ingested per day would be 0,
5.12, 5.58, 1.8, and 14.34 mg for Nature’s Plus,
Nature’s Way, Nature’s Herbs, Rexall, and Enzymatic
Therapy, respectively.
The Enzymatic Therapy dietary supplement contained an extract of the ginger herb. As a result, its
composition was placed on a milligram-per-capsule
basis rather than on a milligram-per-gram basis as
with the other ginger dietary supplements (Table 2).
The capsules from Enzymatic Therapy were found to
contain 4.78 mg of 6-gingerol, 10.23 mg of 6-shogaol,
2.43 mg of 8-gingerol, and 1.62 mg of 10-gingerol.
The label stated that each capsule was standardized to
contain 20.0 mg of 6-gingerol and 6-shogaol. The
6-shogaol concentration also was found to be very
high relative to that of 6-gingerol, 8-gingerol, and
10-gingerol. This indicates that the 6-shogaol concentration of the ginger root was either very high or that
dehydration of 6-gingerol had occurred during processing and/or storage.
DISCUSSION
The ginger root powder dietary supplements from
different sources were found to vary widely in 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol composition. This was found when the concentrations were
expressed on a milligram-per-gram basis or on a
milligram-per-capsule basis. One brand did not con-
VOL. 107, NO. 6, JUNE 2006
tain any 6-gingerol, 8-gingerol, or 10-gingerol. The
6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol
concentrations of the ginger root powders varied 8.1-,
15.6-, 2.8-, and 3.9-fold, respectively. In addition, the
amounts of 6-gingerol in the daily recommended
doses varied from 0 to 14.34 mg. Based on these
calculations, the amounts of 6-gingerol ingested per
serving or per day would not compensate for the
variation in the recommended serving sizes.
Except for the bulk ginger product, all of the
labels on the containers listed the manufacturer, formulation, and, lot number. Three of the 10 ginger
root dietary supplements did not list an expiration
date, 5 did not list a daily serving size, and 7 were not
standardized. The formulations of the different dietary supplements were fairly consistent in that 7 of 8
of the ginger dietary supplements contained either
530 or 550 mg of ginger root powder in each capsule.
There was, however, a greater variation in the recommended serving size per day. The lowest serving size
was 250 mg (Nature’s Plus), whereas the 2 highest
were 4.4 g per day (Nature’s Way) and 4.77 g per day
(Nature’s Herbs). Thus, ginger dietary supplements
must be added to the list of herbal preparations that
vary widely in their composition, in their recommended serving size, in the total number of capsules
to take per day, and in their lack of uniform standardization.
The variation in the gingerol composition and in
the recommended daily serving size of the dietary
supplements examined in this study could impact
their use and acceptance as well as their efficacy and
safety. The German Commission E Monograph recommends 1.0 g of ginger powder per day for treating
loss of appetite, travel sickness, and dyspeptic complaints, but it does not recommend the use of ginger
to treat morning sickness.16 The German Commission
E, however, does recommend that 1.0 g of ginger
powder per day be given for 4 days to treat hyperemesis gravidarum as suggested by Fischer-Rasmussen et al.3,16 One and 1.5 g per day of ginger
powder and 0.5–1.0 g of ginger root extract for 3 days
to 3 weeks were found to be safe and effective in
treating nausea associated with pregnancy in the
double-blind randomized clinical trials cited by
Borelli et al7 and Boone and Shields.6 Caution should
be exercised in following the doses recommended by
health store employees. For example, the dose of
ginger root dietary supplements recommended by
health store employees for treating pregnancy-related
nausea was found to vary widely and to be correct
only 3.6% of the time.17 The labels on 4 of the dietary
supplements examined in this study stated that the
Schwertner et al
Ginger Root Dietary Supplements
1341
supplement can ease discomfort associated with
travel, promote digestive health, support digestive
health, and help maintain a calm stomach. None of
the dietary supplements made a claim that the ginger
powder can be used to reduce nausea associated with
pregnancy. In light of the variation in composition
and serving sizes of the different dietary supplements,
we cannot recommend the use of ginger root dietary
supplements as a treatment for nausea associated with
pregnancy, nor can we recommend a given dose or
duration of treatment.
The cause of the variation of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol composition is not
known, but the variation could be due to the source
and/or age of the ginger, the homogeneity of the
rhizome used, or the method of processing. Even
though 6-gingerol is the principal gingerol, we included information on 6-shogaol, 8-gingerol, and
10-gingerol compositions as well. The chromatographic profiles of 6-gingerol, 6-shogaol, 8-gingerol,
and 10-gingerol might be used to standardize the
ginger dietary supplements as well as the doses.
Additionally, the chromatographic profiles might be
useful in providing information on adulteration, quality of ginger rhizome, efficiency of extraction, and the
effects of processing. In this regard, the ratio of
6-gingerol to 6-shogaol may serve as a marker of
6-gingerol stability and ginger quality. Fresh ginger,
for example, contains very little 6-shogaol, but with
heat and processing, 6-gingerol loses water and is
converted to 6-shogaol.10,11. The source and quality of
the ginger used in the clinical trials were not always
given.2–7 Fresh ginger powder, for example, was used
in 2 of the 4 clinical trials,2,7 yet we do not know if
fresh ginger is better than ginger powder that is not
fresh.
Chemical and chromatographic analyses of the
ginger root powders and extracts used in clinical trials
described in this report have not been performed.2–7
This represents a major limitation of those studies.
Future clinical trials should include information on
the amounts of 6-gingerol, 6-shogaol, 8-gingerol, and
10-gingerol in the ginger root powders and extracts.
Information on other chemical substances should also
be provided if these substances are found to be related
to efficacy, safety, and quality of the ginger root
dietary supplements. Our HPLC method is an excellent method for establishing such concentrations, and
hopefully, such analyses will become standard practice in future clinical trials of dietary supplements. We
would also recommend that the dose per day be
expressed in as many ways as possible. For example,
the dose might be expressed on the amount of
1342
Schwertner et al
Ginger Root Dietary Supplements
6-gingerol or the amount of total 6-, 8-, and 10gingerol given per day as well as on the amount of
ginger root powder or extract given per day. The
duration of treatment also needs to be specified. Such
information would more precisely identify the safest
and most effective dose range. The variation that was
found in the recommended daily dose of the ginger
dietary supplements suggests that the recommended
dose should be reevaluated and standardized as more
definitive clinical data become available.
In this study, we analyzed only ginger dietary
supplements that were available commercially. We
did not evaluate the same ginger dietary supplement
from different stores or with different lot numbers.
Likewise, we did not evaluate products from international sources and the Internet. We did not determine
the gingerol composition of fresh ginger powder, but
we did analyze USP ginger powder as a reference
source. The number of brands analyzed is relatively
small but is believed to be representative of the ginger
root powders. Lastly, we evaluated only 4 out of 50 or
more constituents found in ginger root extracts. Further studies are needed to determine the appropriate
dose of ginger root powders and extracts, the lower
limits of effectiveness, the safety of the ginger root
powders and the extracts, and the bioavailability and
pharmacokinetics of the active ginger constituents.
REFERENCES
1. Kawai T, Kinoshita K, Koyama K, Takahashi K. Anti-emetic
principles of Magnolia obovata bark and Zingiber officinale
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VOL. 107, NO. 6, JUNE 2006
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