Antony Haynes explores the potential mechanisms and actions of arabinogalactans, specifically from the Larch tree.
The reason for choosing this topic is due to the clinical improvements that have been witnessed from its use by numerous patients of my own and of other practitioners.
Larch arabinogalactans will be referred to as “L.A.”.
L.A. is a polysaccharide powder derived from the wood of the larch tree (Larix species) and comprised of approximately 98 percent arabinogalactan. Arabinogalactans are found in a variety of plants but are more abundant in the Larix genus, primarily Larix occidentalis (Western Larch). The Western Larch is unique among pines in that it loses its needles in the fall. The Western Larch is also known by the names of Mountain Larch or Western Tamarack and is native to the Pacific and Inland North-west United States as well as parts of British Columbia, Canada[i].
Description and Biochemistry
Pharmaceutical-grade larch arabinogalactan is a fine, dry, off-white powder with a slightly sweet taste and mild pine-like odour. It dissolves completely in water or juice, is low in viscosity and therefore easy to administer, even to children. It is composed of galactose and arabinose molecules in a 6:1 ratio, with a small amount of glucuronic acid. Arabinogalactans are long, densely branched polysaccharides of varying molecular weights (10,000-120,000). Lower molecular weight polysaccharides typically exhibit an anti-inflammatory, anti-complement, anti-allergy effect, while those of higher weights stimulate natural killer (NK) cell cytotoxicity and reticuloendothelial cells. In the case of larch arabinogalactan, molecular weights of the two major fractions are 16,000 and 100,000, perhaps accounting for its wide range of therapeutic properties[ii].
L.A. is approved by the U.S. Food and Drug Administration (FDA) as a source of dietary fibre, but also has potential therapeutic benefits as an immune stimulating agent and cancer protocol adjunct.
Human studies on the pharmacokinetics of L.A. are scarce and the amount absorbed following an oral dose remains unclear. Animal studies indicate that intravenous injection of purified larch arabinogalactan results in 52.5% of the dose being present in the liver and 30% in the urine 90 minutes after dosing. Hepatic clearance occurred with a half-life of 3.42 days[iii].
Non-absorbed L.A. is actively fermented by intestinal microflora and is particularly effective at increasing beneficial anaerobes such as Bifidobacteria and Lactobacillus[iv].
L.A. is an excellent source of dietary fibre that is able to increase short-chain fatty acid production (primarily butyrate) via its vigorous fermentation by intestinal microfloraii.
It is well documented that butyrate is essential for proper colon health as it is the preferred substrate for energy generation by colonic epithelial cells[v]. Butyrate also acts as a protectant for the intestinal mucosa against disease and cancer-promoting agents[vi].
L.A. added to human faecal homogenates has also been shown to decrease ammonia generation, and therefore may be of clinical value in the treatment of portal-systemic encephalopathy, a disease characterised by ammonia build-up in the liveriv.
L.A. given to human subjects increased levels of beneficial intestinal anaerobes, particularly Bifidobacterium longum, via their fermentation specificity for arabinogalactan compared to other complex carbohydrates[vii].
L.A. may be an effective adjunct to cancer therapies due to its ability to stimulate NK cell cytotoxicity, stimulate the immune system, and block metastasis of tumour cells to the liverii.
Animal studies have demonstrated arabinogalactan’s ability to inhibit or block lectin receptor sites, thereby reducing tumour cell colonisation of the liver and also increasing survival time of the subjects[viii],[ix],[x].
Pretreatment with L.A. was found to stimulate NK cell cytotoxicity via potentiation of the cytokine network, primarily via an increase in the release of gamma interferon[xi].
Paediatric Otitis Media
Recurrent otitis media is common in paediatric populations and it appears that improving immune system function might lead to a decrease in both frequency and severity of this condition. Research has demonstrated larch and other arabinogalactans to be capable of enhancing the immune response to bacterial infection via stimulation of phagocytosis, competitive binding of bacterial fimbriae, or bacterial opsonization. This was found to be particularly true for infection by gram negative organisms such as Escherichia coli and Klebsiella speciesii,[xii].
In addition, D’Adamo reports a decrease in occurrence and severity of otitis media in paediatric patients supplemented prophylactically with larch arabinogalactanii.
L.A.’s mild taste and excellent solubility in water and juice make it a relatively easy therapeutic tool to employ in paediatric populations.
In cell and animal models, L.A. is capable of enhancing natural killer cells and macrophages as well as the secretion of pro-inflammatory cytokines. In a human clinical study, it was demonstrated that L.A. increased the body’s potential to defend against common cold infection. L.A. decreased the incidence of cold episodes by 23 %.
These observations suggest a role for L.A. in the improvement of cold infections, although the mode of action remains to be further explored. Different hypotheses can be envisaged as L.A. can possibly act indirectly through microbiota-dependent mechanisms and/or have a direct effect on the immune system via the gut-associated lymphoid tissue (GALT)[xiii].
A number of chronic diseases are characterised by decreased NK cell activity, including chronic fatigue syndrome[xiv], viral hepatitis[xv],[xvi],[xvii], & autoimmune diseases such as multiple sclerosis[xviii].
Stimulation of NK cell activity by L.A. has been associated with recovery in certain cases of chronic fatigue syndrome[xix]. Viral hepatitis (hepatitis B and C) is also characterised by a decrease in NK cell cytotoxicityxiv, xv and therefore these patients may benefit from its stimulation by L.A.. In the case of multiple sclerosis, a small 2-year study of patients with the relapsing/remitting type concluded that disease severity was correlated with NK cell functional activity, supporting the hypothesis that NK cells play a role in the immunopathogenesis of this diseasexvii.
Consequently, stimulation of NK cell cytotoxicity might be of clinical benefit to these patients. Patients with HIV/AIDS develop low CD4 cell counts and often are plagued by opportunistic infections.
By virtue of its immune-stimulating properties, L.A. has been shown to effect a slight increase in CD4 cell counts, in addition to decreasing susceptibility to opportunistic pathogensii.
Side-Effects and Toxicity
L.A. is a safe and effective immune-stimulating phytochemical. It is FDA-approved for use as a dietary fibre and in food applications. Both acute and long-term toxicity studies in rats and mice reveal no evidence of toxicity[xx].
Human consumption is usually without side-effects; however, a small percentage of people (<3%) experienced bloating and flatulence, possibly due to the vigorous fermentation of the arabinogalactan by intestinal microfloraii.
Due to its excellent safety profile and solubility in water and juice, L.A. is considered a safe, effective immune-supportive agent for paediatric use.
L.A. in powder form is typically dosed in teaspoons or tablespoons at a concentration of approximately 4-5 grams per tablespoon. The typical adult dosage is one to three tablespoons per day in divided doses; the paediatric dose is one to three teaspoons per day. The powder is usually mixed with water or juice but can be added to food if desired.
L.A. has been shown to support immune function, SCFA levels, to act as a prebiotic for gut bacteria particularly Bifidobacteria, and may be of potential benefit in those with CFS, hepatitis, and auto-immune conditions, as well as in paediatric otitis media.
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Great article, very informative. Just what I was after. Thank you. Alaska
Many articles inform about possible dangers to people with an autoimmune sickness. This one does not. Have you looked into this aspect?
Thank you for the enquiry. Larch Arabinogalactans (LAG) is regarded as a very safe ingredient to consume up to 8 grams daily – other than some may experience mild GI symptoms.
There is an hypothesis that “Auto-immune diseases” such as multiple sclerosis (MS), lupus (systemic lupus erythematosus, SLE), rheumatoid arthritis (RA), or other conditions: LAG might cause the immune system to become more active, and this could increase the symptoms of auto-immune diseases.
There is no published evidence to confirm this, and to date this is a suggested not a proven risk – however, if you have an AI disease you may choose to manage your dosing carefully or avoid the clinical use altogether.