Supplement analysis backed by scientific evidence · PT

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Limited evidenceImmunity

Larch Arabinogalactan

Larch arabinogalactan is a well-tolerated soluble fiber with a small cluster of randomized trials suggesting fewer colds and a better antibody response to vaccination. The signal is consistent but the trial base is thin, small, and almost entirely funded by the ingredient's manufacturer.

What the science says

  • Reduces the incidence of common colds Limited evidence

    In a 12-week randomized, placebo-controlled trial of 199 adults, 4.5 g/day of larch arabinogalactan reduced the incidence of cold episodes by roughly 23% versus placebo. It is one adequately sized trial with a single positive endpoint, not a replicated finding, and severity and duration outcomes were less clear-cut.

  • Enhances antibody response to vaccination Limited evidence

    In a randomized, double-blind pilot study, adults taking 4.5 g/day of a proprietary arabinogalactan extract for about 72 days showed a greater rise in antigen-specific IgG to the 23-valent pneumococcal vaccine than placebo, though the effect was serotype-dependent rather than uniform. A later multi-dose study reported similar immunomodulatory effects on antibody response; both were small and manufacturer-sponsored.

  • Acts as a prebiotic fiber Moderate evidence

    Larch arabinogalactan resists human digestion and is fermented in the colon, increasing short-chain fatty acid production and bifidobacteria in human and in vitro work. As a fiber source it is legitimate — it simply competes with cheaper, better-studied prebiotics like inulin and partially hydrolyzed guar gum.

  • Boosts NK cell activity or treats infection Limited evidence

    Immune-cell effects come mainly from in vitro and animal work plus small mechanistic human studies; results across trials have been inconsistent, and an early trial combining it with echinacea could not separate the two. There is no evidence it treats an established infection.

Dosage & safety

Studied doseTrials used 1.5-4.5 g/day, with 4.5 g/day (usually as a single daily powder dose in water or juice, taken for 8-12 weeks) being the dose behind the cold-incidence and vaccine-response results. It is a bland, highly soluble powder, which is why it is also used as a fiber carrier in food products.
SafetyGenerally well tolerated and holds GRAS status in the US as a dietary fiber. Like any fermentable fiber it can cause bloating, flatulence and looser stools, particularly when started at the full 4.5 g dose; ramp up over a week. People with severe pollen or wood-dust allergy should note the botanical source (Larix species). Anyone on immunosuppressive therapy or with an autoimmune condition should be cautious with any product marketed as an immune stimulant, since the human data are too thin to characterize the effect. No meaningful drug interactions are documented, though as with all soluble fibers, separate it from medications by a couple of hours.

Scientific references

Where to buy

Vital Nutrients, Arabinogalactan Powder, 10.6 oz (300 g)

View on iHerb

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