Arabinogalactins, substances found in many plants, are long molecules made of the sugars galactose and arabinose linked together in a chain. Arabinogalactan extracted from the Western larch tree (larch arabinogalactan, or LA) has been proposed as an immune stimulant.
Test-tube and animal studies suggest that LA has several potentially positive effects on the immune system. It appears to activate a type of white blood cell called a “natural killer” or NK cell, and perhaps other white blood cells as well, and also possibly alter levels of immune-related substances such as interleukins, interferon, and properdin. 1-5
On the basis of these findings, LA has been advocated as a supplement for general immune support . However, this recommendation is premature. It is a very, very long way from basic science of this type to evidence that a treatment has real effectiveness. Many plant substances appear to activate the immune system; this may be merely because the immune system regards them as “the enemy,” and mobilizes to fight them. It takes double-blind, placebo-controlled trials to determine whether theoretical effects translate into real life benefits, and thus far only one such study has been performed on LA as an immune stimulant. Unfortunately, this single meaningful trial was not designed to determine the actual medical benefits (if any) of LA. Rather, it primarily continued the theoretical investigation of LA’s effects on components of the immune system.
In this trial, 48 healthy women were assigned to receive one of four treatments: LA, echinacea, LA plus echinacea, or placebo. 6 Researchers evaluated various laboratory measurements of immune function. The results failed to show that LA by itself had any effect on immunity.
Other extremely preliminary research hints that LA might enhance the effectiveness of drugs used in cancer treatment , 7,10 help antibiotics fight ear infections and other infections, and enhance the immune system in people with conditions such as chronic viral hepatitis , HIV , and chronic fatigue syndrome . 5 However, all these suggestions are highly speculative and lack reliable supporting evidence.
There no doubt, however, that LA is a good dietary fiber source. Like less expensive forms of fiber, it appears to have beneficial effects in the colon. 11
Based on animal studies and limited evidence in humans, LA appears to be essentially nontoxic. 13 However, like other sources of dietary fiber, LA might lead to colonic problems like bloating and flatulence.
One additional set of potential risks derives from its supposed benefits: If LA does in fact meaningfully stimulate the immune system, it might be dangerous. The immune system is balanced on a knife's edge. An immune system that is too relaxed fails to defend us from infections; an immune system that is too active attacks healthy tissues, causing autoimmune diseases. If LA truly boosts immunity, it might cause or worsen such conditions as lupus , Crohn’s disease , asthma , Graves’ disease , Hashimoto’s thyroiditis , multiple sclerosis , or rheumatoid arthritis , among other problems. In addition, people who take immune suppressant drugs for organ transplants would be at risk of organ rejection. However, there is no actual evidence that it causes problems.
Maximum safe doses in young children, pregnant or nursing women, or people with severe liver or kidney disease has not been established.
1. 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;10:145–53.
8. 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.
Last reviewed September 2014 by EBSCO CAM Review Board
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