Larch Arabinogalactan Unique Natural Prebiotic for Immune Support Carolyn Perrini, CLS, CNC Larch arabinogalactan is a well known source of dietary fiber that offers powerful therapeutic benefit as a prebiotic and as a modulator of the immune system. Of particular interest is its potential as an adjunctive supplement in the treatment of chronic diseases, including cancer.1 Arabinogalactan (AG) is a polysaccharide found in the cell walls of a wide variety of edible and non-edible, woody plants. The wood of the western larch tree (Larix occidentalis) provides a rich harvest of free arabinogalactan from its inner bark. This complex carbohydrate helps the tree recover from injury from lightning strikes, and protects against the freeze-thaw cycles experienced in the high altitudes of the Pacific and Inland Northwest where it grows.2 Polysaccharides are often found in many medicinal herbs used for immune enhancement, including Echinacea and Astragalus.3 AG is a fine, dry, off-white powder with a mildly sweet taste that mixes well with liquids. This safe and effective phytochemical is FDA approved for use as a dietary fiber and as a food additive. There are no known reports of toxicity. Credit for introducing larch AG into clinical practice goes to the distinguished naturopathic physician, Dr. Peter D’Adamo. AG Supports Digestion Larch AG acts as a food supply to friendly intestinal bacteria. Like the well-known fructooligosaccharides (FOS), AG is considered a “prebiotic.” The non-absorbed fiber is eagerly fermented by the distal gut microflora, resulting in an elevated production of short-chain fatty acids (SCFAs)—primarily butyrate, but also propionate. SCFAs are critically important to the health of the colon and are the principal energy source (butyrate) for the colonic epithelial cells.8,9 Many clinicians use prebiotics to prevent and treat intestinal conditions like diverticulosis, leaky-gut, irritable bowel syndrome (IBS) as well as inflammatory bowel diseases (IBD) like Crohn’s and ulcerative colitis. Studies have shown that larch AG consumption reduces intestinal ammonia generation.5 Reducing ammonia is significant because even low ammonia levels can have damaging effects on intestinal colonic cells.6 AG may especially benefit patients with liver disease who are unable to detoxify ammonia, resulting in hepatic encephalopathy.4,6,7 AG Enhances Immunity While larch AG is important for digestive health it has received even more attention for its ability to promote the health of the immune system. Larch AG seems to enhance immune response and may be termed a biological response modifier.10 Larch AG may be important in cancer treatment protocols due to its ability to block the metastasis of tumor cells to the liver, and to stimulate NK cell cytotoxicity.3 Tumor metastasis to the liver is more common than to other organ sites. AG has been shown to reduce tumor cell colonization and increase survival time of subjects with various cancers.12,13,14 Incidentally, modified citrus pectin has the same anti-metastatic mechanism of action as larch AG, but does not provide the immune-modulating effects. NK cell activity is a functional marker for health. In one well-designed study, larch AG induced an increased release of interferon gamma (IFN gamma), tumor necrosis factor alpha, interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6). This resulted in activating two powerful cells of the immune system: macrophages and NK cells. It was found that the IFN gamma was most responsible for the observed enhancement of NK cytotoxicity.11 Reports in the medical literature link decreased NK cell activity to a variety of chronic diseases including chronic fatigue syndrome,15 viral hepatitis,16,17 HIV/AIDS,3 and autoimmune diseases such as multiple sclerosis.18 The ability of larch arabinogalactans to stimulate NK activity might be the reason for the significantly improved clinical outcome of these patients. Other Indications Larch AG has also been shown to decrease the frequency and severity of pediatric otitis media caused by gram negative rods (especially, Escherichia coli and Klebsiella sp.)3 (Note: Xylitol consumption also reduces the incidence of otitis media.) Dosage Larch arabinogalactan in powder form is typically dosed in teaspoons or tablespoons at a concentration of approximately 3 grams per teaspoon. The adult dosage is one to three teaspoons per day in divided doses. Because of its mild taste and excellent solubility in water or juice, it is easy to use with children. Clinical feedback suggests an occasional reaction of bloating and flatulence in less than three percent of individuals (mostly women). This side effect is probably due to the effect AG has on beneficially altering intestinal microflora and will often disappear after several days to one week.10 References 1. Adams MF, Ettling BV. Industrial Gums 2nd Edition; Academic Press 1973. 2. Chemstone. Theoretical Basis for Process Improvement with Chemstone OAE Technology. 3. D’Adamo P. Larch arabinogalactan is a novel immune modulator. Townsend Letter for Doctors and Patients 1996, July; 156: 42-46. 4. Vince AJ, McNeil NI, Wager JD, Wrong OM. The effect of lactulose, pectin, arabinogalactan, and cellulose on the production of organic acids and metabolism of ammonia by intestinal bacteria in a faecal incubation system. Br J Nutr 1990;63:17-26. 5. Englyst HN, Hay S, Macfarlane GT. Polysaccharide breakdown by mixed populations of human faecal bacteria. FEMS Microbiol Ecology 1987;95:163-171. 6. Robinson R, Feirtag J, Slavin J. Effects of dietary arabinogalactan on gastrointestinal and blood parameters in healthy human subjects. J Amer College of Nutrition 2001; 20: 279-285. 7. Crociani F, Alessandrini A, Mucci MM, Biavati B. Degradation of complex carbohydrates by Bifidobacterium spp. Int J Food Microbiol 1994; 24:199-210. 8. Roediger WE. Utilization of nutrients by isolated epithelial cells of the rat colon. Gastroenterology 1989; 83:424-429. 9.Tsao D, Shi Z, Wong A, Kim YS. Effect of sodium butyrate on carcinoembryonic antigen production by human colonic adenocarcinoma cells in culture. Cancer Res 1983;43:1217-1222. 10. Kelly GS. Larch arabinogalactan: Clinical relevance of a novel immune-enhancing polysaccharide. Alternative Med Rev 1994; 4(2):96-103. 11. Hauer J, Anderer FA. Mechanism of stimulation of human natural killer cytotoxicity by arabinogalactan from Larix occidentalis. Cancer Immunol Immunother 1993;36:237-244. 12. Hagmar B, Ryd W, Skomedal H. Arabinogalactan blockade of experimental metastases to liver by murine hepatoma. Invasion Metastasis 1991;11:348-355. 13. Beuth J, Ko HL, Schirrmacher V,et al. Inhibition of liver tumor cell colonization in two animal tumor models by lectin blocking with D-galactose or arabinogalactan. Clin Exp Metastasis 1988;6:115-120. 14. Beuth J, Ko HL, Oette K, et al. Inhibition of liver metastasis in mice by blocking hepatocyte lectins with arabinogalactan infusions and D-galactose. J Cancer Res Clin Oncol 1987;113:51-55. 15.Levine PH, Whiteside TL,Friberg D, et al. Dysfunction of natural killer cell activity in a family with chronic fatigue syndrome. Clin Immunol Immunopathol 1998;88:96-104. 16. Machado IV, Deibis L, Risquez E, et al. Immunoclinical, molecular, and immunopathologic approach to chronic viral hepatitis.Therapeutic considerations. GEN 1994;48:124-132. [article in spanish]. 17. Corado J, Toro F, Rivera H, et al. Impairment of natural killer (NK) cytotoxicity activity in hepatitis C virus (HCV) infection. Clin Exp Immunol 1997;109:451-457. 18. Kastrukoff LF, Morgan NG, Zecchini D, et al. A role for natural killer cells in the immunopathogenesis of multiple sclerosis. J Neuroimmunol 1998;86:123-133.