Larch

Scientific Name(s): Larix dahurica L., Larix decidua Mill., Larix eurolepis Gord., Larix europaea., Larix gmelinii., Larix kaempferi., Larix laricina Koch., Larix leptolepis (Sieb. et Zucc.) Gord., Larix occidentalis Nutt., Larix sibirica ledeb.
Common Name(s): Larch, Larch gum, Larix, Mongolian Larchwood (L. dahurica)

Medically reviewed by Drugs.com. Last updated on Jan 24, 2022.

Clinical Overview

Use

Arabinogalactan, which is present in some larch species, has been reported to stimulate the immune system and boost antibody response to vaccines. It may be useful in treating upper respiratory infections and dyslipidemia. However, very limited clinical trials, primarily conducted in healthy individuals, support these uses. Larch arabinogalactan is approved by the US Food and Drug Administration (FDA) as a source of dietary fiber and for use in food products.

Dosing

The typical adult dose is 1 to 3 tablespoons/day of larch arabinogalactan powder in divided doses. In children, the typical dose is 1 to 3 teaspoons/day of the powder in divided doses. The powder can be mixed with water or juice, or added to food. Arabinogalactan extract (ResistAid) 1.5 to 4.5 g/day for 60 to 72 days, beginning 30 days prior to vaccine administration, has also been used.

Contraindications

Larch should not be used in patients with autoimmune disorders such as systemic lupus erythematous, Crohn disease, or rheumatoid arthritis due to its stimulating effects on the immune system. Larch is not recommended in patients with tuberculosis because arabinogalactans are structural components of cell walls of mycobacterium.

Pregnancy/Lactation

Avoid use. Clinical information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

Because of its immunostimulating effects, larch should not be used with immunosuppressant drugs.

Adverse Reactions

Most individuals do not experience adverse reactions with larch. However, because larch is a source of dietary fiber, bloating, flatulence, and other mild GI adverse effects may occur.

Toxicology

Larch arabinogalactan is generally recognized as safe (GRAS) and is approved by the FDA as a source of dietary fiber and for use in food products.

Scientific Family

• Pinaceae

Botany

Larch trees are deciduous conifers that lose their needles in the fall. One species, L. decidua, grows up to 50 m in height and has needle-like leaves and small, light-brown cones.1 It is indigenous to the Pacific Northwest United States and British Columbia.2 The Dahurian larch tree (L. gmelinii/L. dahurica) is found in central Siberia and as far east as Kamchatka, Russia.3, 4 Siberian larch (L. sibirica) is also found in Siberia. European larch (L. decidua) is cultivated in central Europe. Japanese larch (L. leptolepis/L. kaempferi) is found in Japan. Eastern larch (L. laricina) and Western larch (L. occidentalis) grow in North America.4

History

Larch trees were reportedly introduced in Great Britain in 1639 and have been cultivated there since the early 19th century. The tree is grown mainly for its timber, but the inner bark and resin are also used.1 Arabinogalactan constituents from certain Larix spp. have gained popularity because of their ability to enhance the immune system.5 Dietary sources of arabinogalactans include carrots, tomatoes, pears, radishes, and red wine.4, 6

Chemistry

Arabinogalactans a...