Labrador Tea
Labrador Tea
This medicinal plant of the Canadian Boreal forest has a rich history of use in the traditional management of diabetes symptoms.
The common name 'Labrador tea' actually refers to three closely related plant species: Rhododendron tomentosum, also known as Northern Labrador tea; Rhododendron groenlandicum, also known as bog Labrador tea; and Rhododendron neoglandulosum, also known as Western Labrador tea. All of these were formerly classified in the genus Ledum but are now classified as Rhododendron. They all belong to the Ericaceae family, also known as the heath family, where we also find blueberries, bilberries, and cranberries. These three species have a long history of use as tea and flavoring ingredients by Native American and First Nations peoples.
In this newsletter issue, we will focus on Rhododendron tomentosum, which is also known by its botanical synonym Ledum palustre. Besides the common name 'Northern Labrador tea,' some people refer to this species as marsh Labrador tea or even wild rosemary or marsh rosemary, although botanically speaking, it is not related to rosemary.
Traditional Uses in Medicine
The medicinal uses of Labrador tea date back to records from at least the 18th century. Its historic uses have included the treatment of ailments such as insect bites, colds, coughs, and rheumatism. Besides its medicinal applications, it is also well-known for its intense fragrance, which can cause headaches in some individuals.
In Europe and Asia, the plant was used in folk medicine for treating bronchitis, lung afflictions, wounds, sore throats, colds, fevers, pain, dysentery, and even leprosy. It was also employed as an insect repellent. In Estonia, whole dried herbs were hung in closets or placed in bedding to deter bedbugs. The Sami people of Norway used decoctions of the plant to treat whooping cough and rheumatism.
In North America, a specific subspecies known as Rhododendron tomentosum subsp. subarcticum (also known under the synonym of Ledum palustre subsp. decumbens) was one of the most popular medicinal plants used by First Nations people. For example, the Inuit and Cree people used it to treat a wide variety of ailments, including respiratory afflictions like colds, coughs, sore throats, shallow breathing, and tuberculosis, as well as painful conditions like headaches, toothaches, rheumatism, inflammations, heart and chest pain, infections, foot sores, and stomachaches. Evaluation of the antidiabetic properties of this species has shown some promise in scientific studies. Even today, in addition to its medicinal applications, it is also valued as a tea for general consumption by many First Nations people.
Interestingly, across parts of Asia where this same subspecies can be found in the wild, it was applied in similar medicinal contexts. For example, in China, the leaves were used to treat infections and inflammation; in Korea, it was used to address women's health issues, and in Tibetan medicine, it was used as a decoction or infusion to treat bronchitis, liver disease, tuberculosis, and as a bath for women's health and gynecological afflictions.
Chemistry and Pharmacology
Most of the scientific literature concerning the chemical makeup of Labrador tea focuses on its essential oil, which is a concentrated preparation of aromatic compounds found in the highly resinous plant. The essential oil is composed of approximately 90 unique compounds, with the major components being the oxygenated sesquiterpenoids ledol, palustrol, and cyclocolorenone. Other major constituents include the fragrant monoterpenes myrcene, cymene, and limonene. As with all other studies on plant essential oils, the composition of the mixture of compounds in a species is heavily influenced by the location where the plant grows, as plants respond to climatic and environmental conditions and stressors through the production of these secondary metabolites. Other compounds found in polyphenolic fractions of the plant include hydroxycinnamic acids, flavonoids, coumarins, and a number of triterpenoids.
Many studies have examined the biological activities of extracts from Labrador tea, demonstrating promising anti-inflammatory and analgesic effects, antimicrobial properties against pathogenic fungi and viruses, antidiabetic properties, antioxidant action, and insecticidal activities. Notably, many of these observed activities align with the traditional uses of the plant in traditional medicine practices.
Safety
The question of toxicology remains a concern in the literature. The sesquiterpenoid compound ledol, found in the plant essential oil, can impact the central nervous system, causing psychomotor stimulation. At substantial doses, it can lead to symptoms such as seizures, paralysis, breathing problems, and even death in extreme cases. These serious adverse reactions are associated with overdosage of ledol. However, concerning the use of Labrador tea as a medicinal or general beverage, ledol found in low concentrations in the beverage is thought to yield restorative or stimulating actions similar to that of caffeine. It's important to remember that caffeine in high doses can also lead to similar central nervous system adverse effects, so ledol is not unique in this aspect.
Several factors can impact the levels of ledol in the final beverage product, including the subspecies used, the means of preparing the beverage (hot versus cold brew), and the environment where it is collected. Based on what has been reported in the literature and the long history of safe use of Labrador tea by indigenous populations across North America, Europe, and Asia as a medicinal beverage, the use of appropriate and non-excessive levels of the tea is recommended.
The Takeaway
In future studies, it would be valuable to see more research undertaken on the safety and medicinal benefits of the actual traditional preparation of Labrador tea, rather than super-concentrated essential oils, which exceed all dose values for typical use in traditional systems of medicine. If you’ve ever used Labrador tea in your health and wellness routine, please share your experiences with it below in the comments! I’d love to learn more from those familiar with it.
Yours in health, Dr. Quave
Cassandra L. Quave, Ph.D. is a scientist, author, speaker, podcast host, wife, mother, explorer, and professor at Emory University School of Medicine. She teaches college courses and leads a group of research scientists studying medicinal plants to find new life-saving drugs from nature. She hosts the Foodie Pharmacology podcast and writes the Nature’s Pharmacy newsletter to share the science behind natural medicines. To support her effort, consider a paid or founding subscription, with founding members receiving an autographed 1st edition hardcover copy of her book, The Plant Hunter.
Available in hardcover, paperback, audio, and e-book formats!
