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Ingredients

Larch Arabinogalactan

Arabinogalactan · Larix occidentalis · Larch arabinogalactan

Snapshot

IndicationsContraindications
  • Gut microbiome composition1
  • Fecal ammonia reduction2
  • Common cold incidence3
  • Vaccine antibody response4
  • Pregnancy or lactation5
  • Egg allergy5

Larch arabinogalactan is a highly branched, soluble polysaccharide from Larix occidentalis with a galactose backbone, recognized as a dietary fiber. Colonic bacteria ferment it, which drives its use as a prebiotic for gut microbiota composition and fecal chemistry1, 2. It is also taken for immune support, mainly by healthy adults with frequent colds and around vaccination, though the immune mechanism remains unclear3, 4.

An earlier trial found more fecal anaerobes and Lactobacillus and less fecal ammonia. In adults with frequent colds, fewer participants were affected by a cold, though symptoms at onset were rated higher. A six-month trial found no lasting effect on serum lipids or glucose. A 2021 in vitro study found human gut microbiota only partly fermented larch arabinogalactan, accumulating acetic and lactic acid while suppressing Enterobacteriaceae and Citrobacter growth6. United States label listings show many products listing larch arabinogalactan, mostly powders, with capsules and tablets; see Form comparison.

Per United States product labels, some warn against use in pregnancy or lactation5. Many others state that individuals taking medication discuss potential interactions with their healthcare professional5.

Last updated October 17, 2026. Read how we make monographs.

In the full monograph

24 sources, 15 studies

  • When to useThe situations practitioners use it for, each with the reason and the study behind it.
  • SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
  • Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
  • How it worksWhat it is and how it works in the body, in plain terms.
  • Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
  • Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
  • Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.
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Sources

  1. 1Effect of arabinogalactan on the gut microbiome: A randomized, double-blind, placebo-controlled, crossover trial in healthy adults.pubmed.ncbi.nlm.nih.govChen, Sudakaran, Blonquist et al. · Nutrition (Burbank, Los Angeles County, Calif.) · 2021 · Pubmed
  2. 2Effects of dietary arabinogalactan on gastrointestinal and blood parameters in healthy human subjects.pubmed.ncbi.nlm.nih.govRobinson, Feirtag, Slavin · Journal of the American College of Nutrition · 2001 · Pubmed
  3. 3Larch arabinogalactan effects on reducing incidence of upper respiratory infections.pubmed.ncbi.nlm.nih.govRiede, Grube, Gruenwald · Current medical research and opinion · 2013 · Pubmed
  4. 4Immunomodulatory effects of ResistAid™: A randomized, double-blind, placebo-controlled, multidose study.pubmed.ncbi.nlm.nih.govUdani · Journal of the American College of Nutrition · 2013 · Pubmed
  5. 5US product labelsdsld.od.nih.govWarnings printed on US dietary supplement labels with this ingredient, from the NIH Office of Dietary Supplements' Dietary Supplement Label Database (DSLD). Manufacturers' precautions, not evidence of harm
  6. 6Prebiotic characteristics of arabinogalactans during in vitro fermentation through multi-omics analysis.pubmed.ncbi.nlm.nih.govSun, Hu, Zhang et al. · Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association · 2021 · Pubmed