Labrador Tea

Generic name: Groenlandicum Nutt. Ericaceae., Ledum Groenlandicum Oeder Ericaceae., Ledum Latifolium Jacq., Ledum Palustre L. Subspecies, Ledum Tomentosum Stokes, Rhododendron Groenlandicum Kron & Judd, Rhododendron Palustre (L.) Kron & Judd, Rhododendron T
Brand names: 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

Usage of Labrador Tea

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)

Labrador Tea side effects

Information is lacking regarding potential adverse Reactions with the use of Labrador tea.

Before taking Labrador Tea

Information regarding safety and efficacy in pregnancy and lactation is lacking.

How to use Labrador Tea

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)

Warnings

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)

What other drugs will affect Labrador Tea

None well documented. In vitro studies have demonstrated inhibitory action on CYP3A4 and 2C isoforms.(Tam 2009, Tam 2014)

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