Promoting health by optimizing immune function is more complicated than just providing the body the nutrition it needs to function well. As immunologists continue to unravel the intricacies of the human immune system, the complexities continue to broaden. Estimates suggest that upwards of 70% of the human immune system resides in the gastrointestinal tract,1 pointing to the significance of healthy gut function in promoting immunity.
Moreover, our gastrointestinal tract is home to trillions of microorganisms, some beneficial and others harmful. A key to health is keeping these residents happy, healthy, and in balance. Thus, optimizing immune health requires an understanding of the interplay between the body’s largest immune organ (the gastrointestinal tract) and its population of microbes, in addition to ensuring that the body and the beneficial organisms are getting the nutrition needed to thrive.
It is in this light that the science of immunology is leading towards therapies that act on the primary factors involved in this dynamic interplay to attain health. This is why probiotics, prebiotics, and direct immune activators are at the forefront of this movement. Probiotics are healthy bacteria that colonize the intestinal tract to maintain its delicate microbial balance. Prebiotics are substances that support the growth of healthy bacteria preferentially to crowd out the less-healthy flora and promote digestive health by enhancing the production of beneficial short-chain fatty acids. And compounds that directly activate or modulate immune processes support health by optimizing multiple aspects of immune function.
Nutritional compounds can uniquely and holistically influence multiple factors of immune health. Several nutritional therapies have the ability to “communicate” with the immune system in both direct and indirect ways, meaning that they interact directly with immune structures while also impacting gut flora immune interactions via prebiotic activity. Three such compounds in particular are larch arabinogalactan (ResistAid), an ingredient from Lonza Ltd. (Switzerland), a dried yeast fermentate complex (EpiCor) from Embria Health Sciences (Ankeny, IA), and yeast-derived beta-glucan (Wellmune) from Biothera (Eagan, MN).
ResistAid is a water-soluble extract from larch trees containing the soluble fiber arabinogalactan and flavonoids with antioxidant activity. Clinical studies on ResistAid have shown its ability to support various facets of immune function. Studies have also investigated the prebiotic benefits of arabinogalactan. Using the SHIME (Simulator of the Human Intestinal Microbial Ecosystem) model—a dynamic in vitro model used to simulate the major compartments of the human digestive tract—researchers evaluated the effect of arabinogalactan (5 g/day for three weeks) on the composition and activity of the microbial environment.2 Arabinogalactan caused a beneficial increase in short-chain fatty acid production with a concomitant decrease in ammonium production, indicating its prebiotic potential. Arabinogalactan further promoted increases in healthy bacteria and decreases in pathogenic Clostridium perfringens.
Arabinogalactan, of course, also shows direct immune-supportive benefits. Linde Riede and colleagues in Berlin recently conducted a study assessing the ability of arabinogalactan (ResistAid) to prevent the common cold and reduce cold symptoms.3 This placebo-controlled clinical trial included 199 healthy adults with recurring upper respiratory tract infections (self-reported occurrence of three infections in the six months prior to enrollment). Participants were assigned to consume 4.5 g of arabinogalactan daily or a placebo for 12 weeks. Three assessments were performed during the study: at baseline, after 6 weeks, and at the end of 12 weeks. In addition, if a participant contracted a cold during the study, a visit occurred at the beginning and on the fifth day of each episode. Participants documented their symptoms for a 14-day period. In the 187 individuals included for analysis (12 were excluded due to significant deviations from protocol), the results indicated that significantly fewer participants in the arabinogalactan group contracted the cold compared to placebo (60% versus 74%). In addition, the percentage of symptom-free days in the treatment group was significantly higher than placebo.
Jay Udani of Medicus Research in Northridge, CA, assessed the immune-modulating activity of larch arabinogalactan (ResistAid) in healthy adults aged 18–61 years.4 This double-blind, placebo-controlled study in 75 individuals assessed the ability of two doses of larch arabinogalactan (1.5 g or 4.5 g/day) or placebo taken for 60 days to influence the immune response to a standardized antigenic challenge. On day 30 of the study, subjects were administered the influenza and tetanus vaccines. The serum response to the antigens was then measured on days 45 and 60 and compared to baseline antibody measurements. While neither treatment group demonstrated any significant elevations in antibodies to the flu vaccine compared to placebo, the participants in the group receiving 1.5 g of the arabinogalactan preparation saw a significant rise in tetanus antibodies versus placebo. No significant difference was noted in the higher-dose group, indicating that a low dose of larch arabinogalactan can augment the immune response to bacterial antigens.
EpiCor is a complex fermentation product from baker’s yeast containing antioxidants, protein, beta-glucans, fiber, polyphenols, vitamins, amino acids, and other metabolites. Several studies attest to EpiCor’s ability to modulate immune function. In a recent investigation led by Sam Possemiers from Ghent University in Belgium, EpiCor was studied using the SHIME model (described earlier) and found to have a prebiotic-like effect on gastrointestinal flora.5 Changes observed included alterations in general flora profile, reduction of pathogenic strains, and increased levels of healthy Lactobacilli and Bifidobacteria. Researchers observed an increase in butyrate production and a significant decrease in pro-inflammatory cytokines.
Clinical studies support EpiCor’s ability to promote a healthy immune response in humans. Mark Moyad, the director of preventive and complementary medicine at the University of Michigan Medical Center, led a study investigating the effects of EpiCor on allergies and allergic rhinitis.6 This 12-week, placebo-controlled trial included 96 healthy subjects with a documented history of seasonal allergies and allergic rhinitis. The subjects received 500 mg of EpiCor daily or a placebo. Participants were examined at baseline and then followed up at 6 and 12 weeks. EpiCor administration significantly reduced the severity of allergic rhinitis symptoms, specifically nasal congestion and runny nose. The EpiCor group experienced 12.5 fewer days of nasal congestion compared to the placebo group and had significantly elevated salivary IgA levels (an antibody associated with enhanced mucosal immunity).