Larch arabinogalactan (AG) is classified as a polysaccharide, or complex sugar. It is considered a prebiotic and a nondigestible/fermentable dietary fiber. The Food and Drug Administration (FDA) has approved Larch AG for uses as a ‘safe and tolerable’ food additive. As a GRAS (Generally Recognized as Safe) direct additive in foods, it is often used as an emulsifier, stabilizer, and for numerous beverage and nutraceutical applications. Larch Arabinogalactan is also used as an alternative sweetener, having a minimal impact on blood insulin levels.
Arabinogalactans are commonly found in various bacteria, fungi, and certain plant species. Echinacea and Shitake mushrooms are among the most well known of organics containing arabinogalactan. The commercial source of Larch AG is harvested from either the Western or Eastern larch tree; though the majority of nutritional supplements contain extracted arabinogalactan proteins from the Western larch tree. Larch arabinogalactan is actually a mixture of several varying arabinogalactans with versatile molecular weights.
It is theorized that the therapeutic properties of Larch AG may be directly influenced by this weight flexibility, especially concerning its two major weight fractions . Why is this relevant? Lower weighted polysaccharides often provide for anti-inflammatory and antiallergy effects, while natural killer (NK) cell cytotoxicity and reticuloendothelial cells are stimulated from higher molecular weights. Larch AG’s unique biological characteristics make it an ideal applicant for various therapeutic implications.
Sources of arabinogalactan include; carrots, corn, pears, radishes, wheat, and other plant sources. Red wine and tomatoes provide for minimal dietary amounts of AG as well. The food additive Gum Arabic is also comprised of branched arabinogalactan. Larch arabinogalactan, however, is principally found in nutritional supplements that have been produced via water extraction of lumen cells found in the Larix genus species of trees. Western Larch trees account for the most abundant forms of supplemental arabinogalactan, affording up to a 98 percent potency of this polysaccharide.
As a prebiotic, Larch arabinogalactan acts as a dietary fiber which, in turn, is then actively fermented by the microflora in the intestines. It is this fermentation process that enables Larch AG to increase the amount of beneficial anaerobes and short-chain fatty acids in different locations along the intestinal tract.  Bifidobacteria and Lactobacillus are among the most critical and beneficial of all the anaerobes produced.  Other beneficial substances actively fermented within the colon from arabinogalactan include the organic acids acetate, butyrate, propionate, lactate, pyruvate, and succinate; and the gases hydrogen, carbon dioxide, and methane.
Butyrate may be the most vital of all short-chain fatty acids. It is integral for maintaining the health of the colon, and is equally important in the production of energy by colonic epithelial cells.  Butyrate may also enhance the body’s ability to protect intestinal mucosa, thereby reducing the risk for damage by disease and cancer causing agents.  Short-chain fatty acids, like butyrate, also decrease ammonia generation and lower the ph levels of the colon. [6, 2] Both of these factors remain important, as they are theorized to provide for a lower incidence of one developing gastrointestinal diseases.
Analogous studies propose that Larch arabinogalactan may lower one’s susceptibility to certain pathogens, while increasing immune stimulating properties. The lower weighted polysaccharide molecules within Larch arabinogalactan are thought to be the primary cause of this increased immunological functioning.  Various epidemiological studies indicate that Larch AG directly stimulates the mononuclear portion of the immune system, increasing the production of monocyte cells.  In clinical application, supplemental Larch AG in dosages of 1.5 and 4.5 grams per day has provided for an increase of circulating peripheral white blood cells and total monocytes.  Monocytes are among the body’s first defense mechanisms to foreign invaders like the organisms/viruses responsible for causing the common cold and flu.
In conjunction with the increase of monocytes and white blood cells, Larch arabinogalactan also enhances the growth of the NK, or natural killer cell activity. These cells are autonomous, and programmed to destroy the cells responsible for the growth of specified tumors and viruses. A healthy population of NK cells may prevent the metastasis of existing cancerous cells to other vital organs.  Natural Killer cell activity is often used as a marker for the overall health of an individual. A decrease in NK cells has been linked to a multitude of various chronic diseases.
Among the various diseases and conditions linked to inadequate NK cell activity:
- Viral Hepatitis is characterized by decreased NK cell cytotoxicity 
- Autoimmune diseases, such as multiple sclerosis
- Larch AG has also been credited with the increased recovery time in certain cases of chronic fatigue syndrome.
There remains no established tolerable upper level intake, or Recommended Dietary Allowance for Larch arabinogalactan. The most common forms of supplementation include both capsules and powders. Pediatric and Adult dosages are variable and range in the scope of 2 - 15 grams daily.
|Dosage Form||Adults and Teenagers||Children up to age 12|
|Capsules >||400 milligrams, 3-4X daily||Based upon bodyweight and individual tolerance|
|Powders >||4-5 grams, 1-3X daily||2 grams, 1-3X daily|
Larch Arabinogalactan is classified as a nonessential nutrient and there remains no report of deficiencies concerning this nutrient in human physiology.
Various long-term mammalian studies have indicated that there is no evidence of toxicity concerning Larch AG supplementation either.  Side effects, however, are experienced in some 3 percent of individuals using arabinogalactan supplements. Persons have reported bloating and an increase of flatulence, mainly caused by the fermentation of AG by microflora of the intestinal tract. 
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