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 tree 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.

Overview

Larch arabinogalactan is approved by the U.S. Food and Drug Administration (FDA) as a food additive and fiber supplement. However, 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 study in mice contradicts this finding. Further studies are needed to identify other uses for larch in humans.

How is it promoted for use?

Proponents believe that larch can be used to treat bronchitis, colds, and other respiratory conditions. Arabinogalactan is promoted 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. Larch resin is recommended to be applied to the skin for wounds and scratches.

What does it involve?

The extract arabinogalactan is a type of complex sugar, called a polysaccharide or glycan, that 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 a type of arabinogalactan.

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 also be bought in capsule and tablet form. Larch resin is available in ointments, lotions, and oils, often in blends with other herbs and oils, for application 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, swelling, and burns. Native Americans used the needles and inner bark to make a tea to treat coughs and constipation. Resin from the bark was 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 substance is also available from other plant sources. The FDA has 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 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 the Western larch stimulated the action of a type of white blood cell called natural killer cells.

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, seeming to contradict the results of the earlier study. With daily injections of arabinogalactan, the mice had fewer white blood cells in the bone marrow after a week. Levels of natural killer cells (a type of white blood cell) went back to normal after 2 weeks of injections. Immune cells in the spleen were mostly present in normal numbers, although the levels of some types of immune cells were lower in the spleen even when they were normal in the bone marrow. Further studies are necessary to determine whether arabinogalactan helps human immune function.

A 2004 human study compared larch arabinogalactan with rice starch to determine whether it improved cholesterol, triglycerides, and sugar levels. At the end of 6 months, there were no differences between the group that received rice starch and the group that received arabinogalactan.

Little scientific information is available on the effects of larch resin mixtures on human skin. It may have antiseptic, or germ-killing, properties.

Are there any possible problems or complications?

This product is sold as a dietary supplement in the United States. Unlike companies that produce drugs (which must provide the FDA with results of detailed testing showing their product is safe and effective before the drug is approved for sale), the companies that make supplements do not have to show evidence of safety or health benefits to the FDA before selling their products. Supplement products without any reliable scientific evidence of health benefits may still be sold as long as the companies selling them do not 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). Though the FDA has written new rules to improve the quality of manufacturing processes for dietary supplements and the accurate listing of supplement ingredients, these rules do not take full effect until 2010. And, the new rules do not address the safety of supplement ingredients or their effects on health when proper manufacturing techniques are used.

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 genus is listed in the FDA's Poisonous Plant Database, although reports of toxic effects were not found in the medical literature. 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 fiber supplement. However, it contains galactose, a type of sugar, and people who require a low-galactose diet should avoid arabinogalactan. Those with lactose intolerance should use the supplement with caution. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.

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 found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).

• Guidelines for Using Complementary and Alternative Methods

• How to Know What Is Safe: Choosing and Using Dietary Supplements

• The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management

• Complementary and Alternative Methods for Cancer Management

• Placebo Effect

• Learning About New Ways to Treat Cancer

• Learning About New Ways to Prevent Cancer

References

Adams J. University of Minnesota researchers uncover immune-boosting fiber. Minnesota Daily. January 7,1999.

Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin, TX: American Botanical Council; 1998.

Bown D. New Encyclopedia of Herbs & Their Uses. New York, NY: DK Publishing Inc; 2001.

Center for Food Safety and Applied Nutrition. Agency response letter: GRAS notice no. GRN 000084. February 19, 2002. US Food and Drug Administration Web site. http://www.cfsan.fda.gov/~rdb/opa-g084.html. Accessed June 6, 2008.

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;10:145-153.

Gruenwald J. PDR for Herbal Medicines. 3rd ed. Montvale, NJ: Thomson PDR; 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.

Larch arabinogalactan. PDRhealth Web site. http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/lar_0320.shtml. Accessed April 23, 2007..Content no longer available.

Larch. PDRhealth Web site. http://www.pdrhealth.com/drugs/altmed/altmed-mono.aspx?contentFileName=ame0368.xml&contentName=Larch. Accessed June 6, 2008.

Larix laricina. US Department of Agriculture Forest Service Web site. http://www2.fpl.fs.fed.us/TechSheets/SoftwoodNA/pdf_files/larixlariceng.pdf. Accessed June 6, 2008.

Lichens. DermNet NZ Web site. http://www.dermnetnz.org/dermatitis/plants/lichen.html. Updated March 18, 2008. Accessed June 6, 2008.

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.

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.

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.

Last Medical Review: 11/01/2008
Last Revised: 11/01/2008