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Other common name(s):
larch arabinogalactan, American larch, Eastern larch, European larch,
common larch, tamarack
Scientific/medical name(s):
Larix occidentalis, Larix laricina, Larix decidua, Larix
europaea
Description
A member of the pine family, the larch has the unusual quality
of losing its needles each fall. Several types of larch tree grow in
central Europe, North America, northern Russia, and Siberia. The bark
and its resin are used in herbal remedies.
An extract of larch called arabinogalactan is sold as an herbal remedy
and fiber supplement. This extract is a type of complex sugar, called a
polysaccharide or glycan, which the body cannot digest.
Arabinogalactans are also found in some common foods such as tomatoes,
wheat, carrots, certain mushrooms, and other plants. The food additive
gum arabic is also a type of arabinogalactan.
Overview
Larch arabinogalactan is already approved by the FDA as a food
additive and as a fiber supplement. Other than that, available
scientific evidence does not support claims that larch bark is
effective in treating cancer or any other disease in humans. Early
laboratory evidence suggested that larch arabinogalactan may stimulate
the immune system. However, a more recent clinical trial in mice
contradicts this. Further studies are needed to find out what other
uses larch may have in humans.
How is it promoted for use?
Proponents believe that larch can be used to treat bronchitis,
colds, and other respiratory conditions. The polysaccharide found in
larch, arabinogalactan, is said to stimulate the immune system and
increase the effectiveness of some drugs (including chemotherapy
medications). Some claim that the compound also inhibits the spread of
cancer to the liver, although available scientific evidence does not
support these claims. Larch resins are recommended to be applied to the
skin for wounds and scrapes.
What does it involve?
Larch arabinogalactan is available as a fiber supplement in
powder form. It can be mixed with water or juice, or sprinkled on food.
It can be bought in capsule and tablet form as well. Larch resin is
available in ointments, lotions, and oils, often in blends with other
herbs and oils to be applied to the skin.
What is the history behind it?
The bark of the larch tree has been used in various folk
medicine traditions to treat rheumatism, jaundice, skin problems, and
as a poultice for wounds, swellings, and burns. Native Americans used
the needles and inner bark to make a tea to treat coughs and
constipation. Resins from the bark were used by Native Americans as a
chewing gum and to relieve indigestion. The resin was also used to
treat kidney and lung disorders, and as a dressing for burns and sores.
Larch arabinogalactan was first isolated from the bark of the
larch tree in 1992, although this fiber is also available from other
plant sources. The US Food and Drug Administration (FDA) approved
arabinogalactan from both the Eastern and the Western larch as a food
additive, so that it can be used in foods as an emulsifier, stabilizer,
thickener, moisture retainer, binder, and for other purposes. It is
also approved as a fiber supplement.
What is the evidence?
In one laboratory ("test tube") study, researchers at the
University of
Minnesota concluded that Larch arabinogalactan is a safe source of
dietary fiber and may be effective in boosting the immune system. The
research was sponsored, however, by the company that owns the patent to
the extract. Another laboratory study done in Germany found that
arabinogalactan from Larix occidentalis stimulated
the action of
natural killer cells (a type of white blood cell).
More recently, a brief animal study looked at white blood
cells that serve important immune functions. The researchers found that
arabinogalactan actually seemed to suppress production of some of these
white blood cells. With daily injections of arabinogalactan, the mice
had fewer white blood cells in the bone marrow after a week. Natural
killer cells went back to normal after 2 weeks of injections. Immune
cells in the spleen were mostly present in normal numbers, although
some were lower in the spleen even when they were normal in the bone
marrow. Further studies are necessary to find out if arabinogalactan
helps human immune function.
A 2004 human study compared larch arabinogalactan with rice
starch to see if it improved cholesterol, triglycerides, and sugar
levels. At the end of 6 months, there were no differences between the
group that received the rice starch and the group that got
arabinogalactan.
Little scientific information is available on the effects of
larch resin mixtures on human skin. It may have antiseptic
(germ-killing) properties.
Are there any possible problems
or complications?
This product is sold as a dietary supplement in the United
States. Unlike drugs (which must be tested before being allowed to be
sold), the companies that make supplements are not required to prove to
the Food and Drug Administration that their supplements are safe or
effective, as long as they don't claim the supplements can prevent,
treat, or cure any specific disease.
Some such products may not contain the amount of the
herb or substance that is written on the label, and some may include
other substances (contaminants). Actual amounts per dose may vary
between brands or even between different batches of the same brand.
Most such supplements have not been tested to find
out if they interact with medicines, foods, or other herbs and
supplements. Even though some reports of interactions and harmful
effects may be published, full studies of interactions and effects are
not often available. Because of these limitations, any information on
ill effects and interactions below should be considered incomplete.
Larch has been approved by Germany’s Commission E for external
use, and is recommended for colds, coughs, and bronchitis.
The larix species is listed in the FDA's Poisonous Plant
Database, although reports of toxic effects in the medical literature
were not found. One source notes that kidney damage might occur if the
bark is ingested or if the oils are spread over a large area of the
body and absorbed through the skin.
Larch allergies have not been reported; however, rashes,
hives, and contact dermatitis have occurred in people working with some
species of larch. It is possible that many of these reactions are due
to contact with lichens that grow on the bark of the larch rather than
the larch itself.
The larch extract arabinogalactan is generally recognized as
safe and is approved by the FDA as a food additive and a fiber
supplement. It contains galactose, however, and people who require a
low galactose diet should avoid arabinogalactan. Those with lactose
intolerance should use the supplement with caution.
Additional Resources
More Information from Your
American Cancer Society
The following information on complementary and alternative
therapies may also be helpful to you. These materials may be ordered
from our toll-free number (1-800-ACS-2345).
References
Adams J. University of Minnesota researchers uncover
immune-boosting fiber. Minnesota
Daily. January 7, 1999.
Bown D. Encyclopedia of Herbs & Their Uses.
New York, NY: DK Publishing Inc; 1995.
Currier NL, Lejtenyi D, Miller SC. Effect over time of in-vivo
administration of the polysaccharide arabinogalactan on immune and
hemopoietic cell lineages in murine spleen and bone marrow. Phytomedicine.
2003 Mar;10(2-3):145-53.
DermNet NZ. Lichens. Available at: http://www.dermnetnz.org/dermatitis/plants/lichen.html. Accessed April
23, 2007.
Gruenwald J, Brendler T, Jaenicke C, eds. PDR for Herbal Medicines, Third
Edition. Thomson PDR, Montvale NJ, 2004.
Hauer J, Anderer FA. Mechanism of stimulation of human natural killer
cytotoxicity by arabinogalactan from Larix occidentalis. Cancer Immunol Immunother.
1993;36:237-244.
Marett R, Slavin JL. No long-term benefits of supplementation with
arabinogalactan on serum lipids and glucose. J Am Diet Assoc.
2004;104:636-639.
PDRhealth.com. Larch arabinogalactan. Available at:
http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/lar_0320.shtml.
Accessed April 23, 2007.
PDRhealth.com. Larch. Available at:
http://www.pdrhealth.com/drug_info/nmdrugprofiles/herbaldrugs/101670.shtml.
Accessed 4/23/07.
Robinson RR, Feirtag J, Slavin JL. Effects of dietary arabinogalactan
on gastrointestinal and blood parameters in healthy human subjects. J Am Coll Nutr.
2001;20:279-285.
US Department of Agriculture Forest Service. Larix laricina. Available
at:
http://www2.fpl.fs.fed.us/TechSheets/SoftwoodNA/pdf_files/larixlariceng.pdf.
Accessed April 23, 2007.
US Food and Drug Administration Center for Food Safety and Applied
Nutrition. Agency Response Letter: GRAS Notice No. GRN 000084.
Available at: http://www.cfsan.fda.gov/~rdb/opa-g084.html. Accessed
April 23, 2007.
Note: This information may not
cover all possible claims, uses, actions, precautions, side effects or
interactions. It is not intended as medical advice, and should not be
relied upon as a substitute for consultation with your doctor, who is
familiar with your medical situation.
Revised: 06/29/2007
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