Larix occidentalis · supplement
Evidence tier: limited
A prebiotic fibre that doubles as an immune modulator, particularly useful in children and elderly.
As a soluble fibre it is fermented by colonic bacteria into short chain fatty acids, and that part is genuinely established in humans. The immune story bolted onto it, that it activates natural killer cells and macrophages and boosts antibody responses, comes from cell and animal models plus small antibody surrogate studies in people. The Lonza funded review of the ingredient concedes that the exact mode of action is not yet completely understood and further studies are required. So: proven as a fibre, hypothesis as an immune agent.
Limited. What is established is that larch arabinogalactan is a fermentable soluble fibre, and it holds FDA GRAS status as a source of dietary fibre. GRAS is a food safety status, not an efficacy finding, and it must never be presented to a consumer as an FDA endorsement of immune benefit. The prebiotic effect has one real human randomised trial, a 30 person crossover at 15 g daily for 6 weeks that shifted the Firmicutes to Bacteroidetes ratio and nudged Bifidobacterium upward. Everything else, and in particular the immune reputation this ingredient trades on, is thinner than its marketing. The single cold incidence trial, 199 healthy adults on 4.5 g daily for 12 weeks (PMID 23339578), MISSED ITS PRIMARY ENDPOINT: in the full analysis set arabinogalactan only TENDED to decrease the incidence of the common cold, at p equal to 0.055. The widely repeated 23 percent reduction in colds comes from the per protocol analysis, the weaker and more bias prone analysis set, and it is quoted as though it were the headline result when it is not. The same trial reported an unfavourable finding that the marketing never mentions: symptom severity at the start of an episode was significantly HIGHER after arabinogalactan supplementation (p equal to 0.028). The remaining immune trials measure antibody titres rather than actual infection, which is a surrogate endpoint, and they are small pilots. Every immune trial and even the main review of this ingredient was financed by Lonza, the company that sells the branded material, and there is NO independent replication of any immune outcome. NCCIH has no monograph on it.
1.5 to 4.5 g daily in the immune trials; up to 15 to 30 g daily when used as a fibre, and tolerated at 30 g daily for 6 weeks. Expect the gastrointestinal effects of any fermentable fibre, meaning bloating and flatulence.
1.5 to 4.5 g daily mixed in water or food.
Very safe. May cause mild gas initially as gut bacteria adapt.
Pregnancy: caution
Breastfeeding: caution
Active compounds: type II arabinogalactan polysaccharide
Remedies using Larch Arabinogalactan · Browse by body system · Check it against what you take
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.