Labrador Tea
Scientific Name(s): Groenlandicum Nutt. Ericaceae., Ledum groenlandicum Oeder Ericaceae., Ledum latifolium Jacq., Ledum palustre L. subspecies, Ledum tomentosum Stokes, Rhododendron groenlandicum [Oeder] Kron & Judd, Rhododendron palustre (L.) Kron & Judd, Rhododendron tomentosum Harmaja
Common Name(s): Bog Labrador tea, Haida tea, Hudson's Bay tea, Indian tea, James tea, Labrador tea, Marsh Labrador tea, Marsh rosemary, Marsh tea, Muskeg tea, Peatbog rosemary, Swamp tea, Tundra tea
Medically reviewed by Drugs.com. Last updated on Jul 1, 2022.
Clinical Overview
Use
Labrador tea has been used historically and in folk medicine for a variety of conditions. However, clinical trial data are lacking to recommend use for any indication.
Dosing
Clinical data are lacking to support dosing recommendations for Labrador tea.
Contraindications
Contraindications have not been identified.
Pregnancy/Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Interactions
None well documented.
Adverse Reactions
Information is lacking regarding potential adverse reactions with use of Labrador tea.
Toxicology
Labrador tea has narcotic properties. High concentrations have been associated with symptoms of intoxication that can lead to paralysis and death. Labrador tea is considered mildly toxic and should be consumed in small quantities only.
Scientific Family
- Ericaceae (heath)
Botany
L. groenlandicum is a short (50 to 200 cm), aromatic, evergreen shrub primarily found in patches in Alaska, Greenland, and Canada, where it thrives in wet, peaty soils. It has bright-green, alternate oblong leaves 2.5 to 7.6 cm in length and with a leathery adaxial surface. The leaves are rolled and have a bluntly pointed tip. Younger leaves point upwards with a white, pubescent abaxial surface, while older reddish leaves point downwards and have a rust-colored abaxial side. The small (12 mm), white, bell-shaped, scented flowers grow from slender stalks in dense terminal clusters. The fruit is a many-seeded, brown, woody capsule.(Hutchens 1991, Stuart 1987, Turner 1997) R. tomentosum (previously L. palustre L.) is distributed mainly in northern and central Europe, North America, and North Asia.(Benelli 2020) The species Ledum glanduosum Nutt. Ericaceae is not found on the coasts or mid-elevations, unlike L. groenlandicum, which is more widespread.
Related/similar drugs
turmeric, Ginkgo Biloba
History
The common name "Labrador tea" derives from its profuse growth in the swamps of Greenland and Labrador. "Hudson’s bay tea" probably derives from the Hudson Bay traders, who sold the leaves for tea.(Turner 2005)
The Haida people used Labrador tea for medicinal purposes, and also picked the leaves (before the shrubs would flower or in late summer), then would dry and boil the leaves for tea.(Turner 2005) During the American Revolution, it was one of several herbs used as a pleasant-tasting substitute for commercial tea. In the 18th century, R. tomentosum leaves were used in German breweries to make beer more intoxicating.(Dampc 2015)
Labrador tea has been used in folk medicine for cough, chest and kidney conditions, headache, rheumatism, diarrhea, sore throat, female disorders, and malignancies. The leaves of L. groenlandicum have been used as an astringent and to treat dysentery and diarrhea.(Belleau 1993, Duke 1985, Hutchens 1991, Stuart 1987) A stronger decoction has been recommended externally for itching and redness of skin (eg, poison ivy). The leaves as a tea have also been used in heart diseases, and for indigestion, diarrhea, and to ease childbirth.(Hutchens 1991, Turner 1997)
Labrador tea is considered rare and an endangered species; the plant is generally under protection in many countries.(Benelli 2020)
Chemistry
Reported constituents of L. latifolium include tannic acid, arbutin, resin, and mineral salts.(Stuart 1987) Leaves contain volatile oil 0.3% to 2.5%, including the sesquiterpenes ledol and palustrol (ledum camphor), with valeric and other volatile acids, ericolin, and ericinol.(Duke 1985)
Uses and Pharmacology
Antidiabetic activity
Weak partial agonistic (compared to rosiglitazone) as well as antagonistic effects on adipogenesis have been demonstrated with R. groenlandicum ethanolic leaf extract in some in vitro studies(Ouchfoun 2016), while strong adipogenic effects have been noted by others. Adipogenic effects have been described for (+)-catechin, (-)-epicatechin, and quercetin, in decreasing order of potency, with the combination of the first 2 yielding the highest adipogenic potential.(Eid 2016)
Animal and in vitro data
In one study, R. tomentosum extract was found to possess some antidiabetic activity, including inhibition of glucose uptake (in normoglycemic rats) and reduced expression of the SGLT1 protein (in CaCo2/15 cells).(Nistor Baldea 2010) In an obesity mouse model, R. groenlandicum ethanolic leaf extract was found to attenuate insulin resistance when administered over 8 weeks while mice were fed a high-fat diet. Compared to untreated obese controls, blood glucose was reduced up to 30% and was not significantly different from normal controls, while insulin serum levels decreased up to 66% and homeostasis model assessment index by 75% (P<0.05 each). Liver steatosis and liver triglycerides were also significantly reduced by the extract (P<0.05). In contrast, weight gain, food intake, and circulating lipid parameters (ie, trigylcerides, low-density lipoprotein, high-density lipoprotein, total cholesterol) remained similar to untreated controls. The mechanism appeared to be related to both a reduction in hepatic gluconeogenesis plus enhanced muscle glucose uptake.(Ouchfoun 2016) A non-significant reduction (23%) in renal dysfunction (ie, microalbuminuria) was reported in an obese prediabetic mouse model treated with R. groenlandicum with significant improvements and normalization of renal fibrosis observed.(Li 2016)
Antimicrobial activity
In vitro data
The essential oil from Labrador tea has been shown to be highly effective against oral bacterial pathogens in vitro, including Fusobacterium nucleatum, an oral pathogen that releases volatile sulfur compounds (VSCs) associated with halitosis. The respective minimum inhibitory and minimum bactericidal concentrations were 0.25% and 0.5% (v/v), and all tested concentrations significantly reduced VSCs without negatively affecting cell viability. However, no significant effect was found on biofilm viability.(Ben Lagha 2020) A supercritical CO2 extract of L. palustre demonstrated strong antimicrobial activity against Staphylococcus aureus and Candida albicans.(Korpinen 2021)
Antioxidant activity
In vitro data
Antioxidant activity has been demonstrated with an ethanolic L. palustre corum extract in vitro. However, in contrast to Melilotus officinalis, coumarins extracted from L. palustre did not exhibit protective effects against ionizing radiation.(Antropova 2020)
Cancer
Animal and in vitro data
An acetone extract of R. tomentosum leaves demonstrated the strongest effect against acute myeloid leukemia (AML) cells in vitro compared to the chloroform, isopropanol, and aqueous ethanol extracts, whereas the water-based extract had no anti-AML effects. Subsequent assessments in mice and primary human AML samples confirmed the beneficial effects of the organic extractions with substantial interpatient variability demonstrated among the human AML samples.(McGill 2018)
Homeopathic use
Homeopathic use of Labrador tea for various ailments (eg, insect bites and stings, acne, prickly heat, varicella, wounds) has been described. Homeopathic uses also include for treatment of asthma, hand and foot pain, gout, rheumatism, ear inflammation, tinnitus, and tuberculosis.(Hutchens 1991)
In an American Academy of Ophthalmology systematic review of the medical literature on various homeopathic agents studied after 1990 for reducing ecchymosis after oculofacial or laser surgery, no studies using L. palustre and meeting inclusion criteria were identified.(Tao 2022)
Insecticidal activity
In vitro data
Mosquito larvicidal activity comparable to that with Mentha species (an active ingredient in some botanical insecticides) was observed for the essential oil of L. palustre. Little to no mortality was noted on non–target aquatic and terrestrial invertebrates, while moderate cytotoxic effects were observed on human keratinocyte and fibroblast cell lines.(Benelli 2020)
Rheumatoid arthritis
In vitro data
In synovial cells isolated from rheumatoid arthritis (RA) patients undergoing synovectomy, the essential oil of R. tomentosum exhibited an antiproliferative effect on human T cells and monocytes/macrophages known to infiltrate the synovium in RA-affected joints.(Jesionek 2019)
Transdermal drug delivery
In vitro data
In an in vitro skin permeation test, the essential oil of L. palustre var. angustrum demonstrated significant transdermal enhancement of donepezil skin permeation compared with controls.(Nan 2018)
Dosing
Clinical data are lacking to support dosing recommendations for Labrador tea.
The leaves are the most commonly used part for medicinal teas and decoctions, and are prepared by brewing in hot or boiling water.(Tam 2014) Labrador tea is commonly made by adding 1 teaspoonful (5 mL) of dried leaves to 1 cup (250 mL) of boiling water, brewed for 3 to 10 minutes; the leaves should be removed. However, safety data are lacking; due to potential for toxicity (eg, from ledol content), Labrador tea should be consumed in small quantities only (has not been defined but less than 1 cup a day of tisane has been suggested).(Dampc 2015)
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Interactions
None well documented. In vitro studies have demonstrated inhibitory action on CYP3A4 and 2C isoforms.(Tam 2009, Tam 2014)
Adverse Reactions
Information is lacking regarding potential adverse reactions with the use of Labrador tea.
Toxicology
Labrador tea is considered mildly toxic and should be consumed in small quantities only. Reported acceptable amounts include 1 teaspoonful (5 mL) of dried leaves for 1 cup (250 mL) of boiling water; brewing times range from 3 to 10 minutes, according to tisane strength preference, but should not exceed 15 minutes.(Dampc 2015)
Labrador tea has narcotic properties. Evidence suggests that excessive use of the tea may cause delirium or poisoning.(Stuart 1987) Toxic terpenes of the essential oils cause symptoms of intoxication (eg, slow pulse, lowering of blood pressure, lack of coordination, convulsions, paralysis, death).(Belleau 1993, Jansen 2012, Turner 1991, Turner 1997)
Kalmia polifolia and Andromeda polifolia are similar to Ledum and can be toxic due to higher concentrations of similar compounds. These plants are distinguished by their glabrous leaves and pink flowers.(Turner 1997)
Index Terms
- Andromeda polifolia
- Kalmia polifolia
- Ledum glanduosum Nutt. Ericaceae
References
Disclaimer
This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.
This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.
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