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Overview: Larch arabinogalactan is a type of soluble dietary fiber taken from the wood of North American larch trees. People often take larch arabinogalactan to support the immune system, but evidence for this use is limited. It is also used as a prebiotic fiber to support gut health, but the benefits for these or other uses are not well defined. Like other fibers, it may cause mild digestive symptoms such as gas or bloating in some people, especially at higher doses. Before taking larch arabinogalactan, tell your health care provider about any health conditions you have and any medicines you are taking.

Uses

What is larch arabinogalactan used for?

Larch arabinogalactan supplements are commonly used to support the immune system and to help lower the chance of getting a common cold. Some research suggests it may slightly lower the chance of catching a cold, but the evidence is limited. It does not appear to make colds less severe.

Larch arabinogalactan is also used for other purposes, including the following, though the benefits are not well defined.

Note: The FDA has not reviewed larch arabinogalactan sold as a dietary supplement for safety and effectiveness. Learn more about dietary supplements here. Larch arabinogalactan may also be added to foods and drinks, such as to improve thickness, texture, and stability, or as a source of dietary fiber. It is generally recognized as safe (GRAS) by the FDA for use in foods. Learn more about GRAS status here.

How does larch arabinogalactan work (mechanism of action)?

Larch arabinogalactan is a soluble fiber. It is a large, densely branched sugar molecule (a polysaccharide) made mostly of two natural sugars, arabinose and galactose. It is taken from the wood of North American larch trees, mainly the western larch (Larix occidentalis) and the eastern larch (Larix laricina). Arabinogalactan is also found naturally in many common vegetables and in some medicinal herbs, and people have eaten it for a very long time as part of a normal diet.

Larch arabinogalactan is not broken down by the body’s digestive enzymes in the stomach and small intestine. Instead, it passes into the large intestine (colon) mostly intact, where the bacteria that live there break it down. This is why it is called a prebiotic. In some laboratory and clinical studies, larch arabinogalactan changed the balance of bacteria in the gut and lowered stool levels of ammonia, a waste product made by gut bacteria. What these changes mean for overall health is not yet clear.

Most of the human research for larch arabinogalactan has used one specific product, so results may not apply to all larch arabinogalactan supplements. Researchers believe larch arabinogalactan may support the immune system in more than one way. It may act indirectly by changing the gut bacteria, which are closely tied to immune function. It may also act more directly on the immune tissue that lines the gut, known as the gut-associated lymphoid tissue (GALT). In laboratory and animal research, larch arabinogalactan increased the activity of certain immune cells and affected immune signals called cytokines. In people, it has been shown to increase the antibody response to certain vaccines (but not others), which points to an effect on the immune system. However, the exact way larch arabinogalactan works is still not fully understood.

The immune-support effects of larch arabinogalactan are among its better-studied uses. Its effects on gut bacteria are also supported by some clinical studies, but what these changes mean for overall health is not well defined. For its other uses, evidence in humans is limited.

Some people take larch arabinogalactan hoping to lower their cholesterol levels. However, its use for this purpose is not supported by available human studies.

Larch arabinogalactan supplements are natural products. The amount of fiber and the exact makeup of a specific product can vary depending on how it is made and how much is in each dose. These differences may change the effects and side effects of one product compared to another.

How should I store larch arabinogalactan?

You should store larch arabinogalactan according to the product label. Most products should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of larch arabinogalactan?

The most common side effects of larch arabinogalactan are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

  • Gas 
  • Bloating or a feeling of fullness
  • Mild stomach cramps or discomfort
  • Changes in bowel movements

There may be other side effects of larch arabinogalactan that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of larch arabinogalactan?

While less common, the most serious side effects of larch arabinogalactan are described below, along with what to do if they happen.

Severe Allergic Reactions. Larch arabinogalactan may cause allergic reactions, which can be serious. Stop taking larch arabinogalactan and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use larch arabinogalactan?

Allergies to Ingredients. People who are allergic to any of the following should not take larch arabinogalactan.

  • Arabinogalactan
  • Larch arabinogalactan
  • Larch (Larix) trees or their products
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific larch arabinogalactan products they stock.

What should I know about larch arabinogalactan before using it?

Larch arabinogalactan may be added to foods and drinks, such as to improve thickness, texture, for stability, or as a source of dietary fiber. It is also available as a dietary supplement. These products cannot be marketed to treat or cure a disease.

Larch arabinogalactan is available in a few forms. The most common form is a powder that dissolves in water or another drink. It is also sold as capsules. Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

If you use a powder, follow the label for how to measure a dose, usually by a scoop or by weight in grams. Larch arabinogalactan powder dissolves well in liquids. As with other fibers, it is a good idea to take it with plenty of water.

Keep larch arabinogalactan out of the reach of children.

The FDA has not tested larch arabinogalactan products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using larch arabinogalactan?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if larch arabinogalactan is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have or have had any of the following.

Other Medicines and Supplements. Before taking larch arabinogalactan, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how larch arabinogalactan could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if larch arabinogalactan passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does larch arabinogalactan interact with foods or drinks?

Interactions with larch arabinogalactan and foods or drinks have not been well studied.

It is unknown if drinking alcohol will affect larch arabinogalactan.

Does larch arabinogalactan interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using so they can watch for any potential interactions.

In particular, make sure that you discuss if you are using any of the following before taking larch arabinogalactan.

  • A medicine that suppresses your immune system, such as azathioprine (Imuran), cyclosporine (Neoral, Sandimmune), mycophenolate (CellCept), sirolimus (Rapamune), or tacrolimus (Prograf)
  • A corticosteroid, such as dexamethasone, methylprednisolone, or prednisone, which is a medicine for certain inflammatory conditions

Like other soluble fibers, larch arabinogalactan might affect the absorption of some medicines, though this has not been studied specifically for larch arabinogalactan. Tell your health care provider about all medicines that you take or have recently taken.

The interactions between larch arabinogalactan and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with larch arabinogalactan is incomplete. Always check with your health care provider before taking larch arabinogalactan with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much larch arabinogalactan?

If you or someone else has used too much larch arabinogalactan, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Read the product label closely, and speak with a health care provider about how to use larch arabinogalactan safely. Do not take double or extra doses, even if you miss a dose.