Benefits
Immune defenses during cold season
In 199 healthy adults who reported frequent colds, 4.5 g/day for 12 weeks did not significantly lower the main measure, cold incidence (p = 0.055), though fewer people had at least one doctor-confirmed cold (p = 0.038). Symptoms at the start of a cold were rated as more severe with arabinogalactan. Effects on flu have not been shown.
Vaccine antibody response
In a 45-person pilot funded by Lonza (4.5 g/day), the antibody response to a pneumococcal vaccine was higher than with placebo for 2 of 7 measured strains. In a 75-person trial, 1.5 g/day raised tetanus antibodies more than placebo but 4.5 g/day did not, and neither dose changed flu vaccine antibodies. Antibody levels are lab markers, not proof of fewer infections.
Gut Microbiome Modulation
In a 30-person crossover trial co-authored by Lonza staff (15 g/day for 6 weeks), the ratio of Firmicutes to Bacteroidetes bacteria fell and Bifidobacterium tended to rise, while overall bacterial diversity fell. Bowel habits, stool consistency and digestive comfort did not change. The trial measured microbiome composition, not a gut health outcome.
Water-extracted larch fiber
According to its trial reports, ResistAid is extracted from the wood of the larch tree with a patented water-based process. It is a highly branched polysaccharide made of galactose and arabinose in about a 6:1 ratio.
Fermentable dietary fiber
Arabinogalactan is a non-digestible carbohydrate that reaches the colon, where gut bacteria ferment it. In the human ResistAid microbiome trial, three minor fecal fatty acids (isovaleric, valeric and hexanoic) were lower after ResistAid, and no gut symptoms changed at 15 g/day.
Mechanism of action
Natural killer cell activity in lab studies
In cultured human blood cells, larch arabinogalactan increased natural killer cell activity against target cells, an effect that depended on interferon gamma. In the human ResistAid vaccine pilot, white blood cell counts, inflammatory cytokines and complement did not change.
Antibody response to some vaccines
Trials suggest ResistAid may boost antibody responses to some bacterial vaccine antigens (two pneumococcal strains, tetanus at the lower dose) but not to flu vaccine. How this happens is not known.
Colonic fermentation
As a non-digestible fiber, arabinogalactan passes to the colon, where bacteria ferment it. Effects on the gut barrier have not been tested in people.
Gut Microbiome Modulation
In a 6-week human trial, ResistAid increased Bacteroidetes and decreased Firmicutes, tended to raise Bifidobacterium and lowered overall microbial diversity; Lactobacillus was not reported to rise.
Clinical trials
Randomized, double-blind, placebo-controlled trial in 199 healthy adults reporting about three colds in 6 months; ResistAid 4.5 g/day (n = 101) or placebo (n = 98) for 12 weeks (Riede et al. 2013, Curr Med Res Opin)
199 healthy adults prone to colds.
Cold incidence, the main outcome, was not significantly lower in the full analysis set (p = 0.055). The number of participants with a cold was significantly lower (p = 0.038), and incidence was significantly lower in the per-protocol set. Symptom severity at the start of an episode was higher on arabinogalactan (p = 0.028). Tolerability did not differ from placebo.
Randomized, double-blind, placebo-controlled pilot in 45 healthy adults; ResistAid 4.5 g/day for 72 days with a 23-valent pneumococcal vaccine on day 30 (Udani et al. 2010, Nutr J)
45 healthy adults not previously vaccinated against pneumococcus.
IgG response was significantly greater than placebo for 2 of 7 measured strains (18C and 23F); the other five strains, salivary IgA, white blood cell count, inflammatory cytokines and complement did not differ. Antibody titers are a surrogate, not fewer infections. Lonza supplied the product and funded the study.
Randomized, double-blind, placebo-controlled crossover trial in 30 healthy adults; ResistAid 15 g/day or maltodextrin for 6 weeks (Chen et al. 2021, Nutrition)
30 healthy adults.
Compared with placebo, the fecal Firmicutes-to-Bacteroidetes ratio fell and Bifidobacterium tended to rise, but overall microbial diversity decreased and three minor fecal fatty acids fell. Bowel habits, stool consistency and digestive symptoms did not change. Two authors were Lonza employees.