On The Shelf
Mickie Cathers
Stinging nettle (Urtica dioica) is a perennial plant traditionally used for hundreds of years to treat a wide range of ailments, from joint and muscle pain, eczema, arthritis, gout, and anemia to dandruff, scurvy, and even snake bites. More recently, nettle is being used to address the early stages of an enlarged prostate, UTIs, hay fever, osteoarthritis, sprains and strains, tendonitis, and even signs of aging. Are there really 101 uses for stinging nettle?
Background and function
Nettle grows worldwide in mild to temperate climates, and it is widespread in Europe, Africa, Asia, and North America. This herbaceous shrub prefers nitrogen-rich soil in open or partly shady habitats with plenty of moisture and is found by rivers or streams. Nettle blooms in June through September, sporting small, greenish-white petals. It is also covered in hairs which can sting when rubbed against the skin. Nettles are considered weeds due to their rapid growth and soil coverage but have been shown to improve overfertilized and metal-rich soils, provide health benefits, and they have even been used to create textiles, as seen during World War I.
Stinging nettles represent a rich source of nutrients and contain a significant number of biologically active compounds, including terpenoids, carotenoids (i.e., β-carotene, lutein, and lycopene) and fatty acids as well as various essential amino acids, chlorophyll, vitamins, tannins, carbohydrates, sterols, polysaccharides, proteins, and minerals (i.e., calcium, iron, zinc, and magnesium).
Is there a benefit?
Stinging nettle has been extensively studied for various pharmacological properties and biological activity in treatment of many different symptoms. A 2020 review in Progress in Biophysics & Molecular Biology by Dhouibi and colleagues dove into nearly 40 years of research to support the clinical and significant value of nettle’s myriad qualities and uses.
Recently, a 2022 review in Evidence-Based Complementary and Alternative Medicine by Taheri and colleagues confirmed these findings as the authors explored evidence that stinging nettle exerts antiviral, antimicrobial and antifungal, anticancer, antioxidant, and anti-inflammatory effects. Analysis of the data also showed evidence of antiaging benefits through an elastase and collagenase enzyme inhibition assay created by a high content of quercetin and ursolic acid.
Nettle’s antiallergic effect through the release of histamine and the inhibition of mast cell tryptase and prostaglandin formation was reported in several studies. Efficacy studies also highlighted nettle’s antimicrobial activity against both Gram-positive and -negative bacteria and yeasts. Anti-inflammatory effects of stinging nettle extract seem to be tied to its inhibitory effect on NF-kB activation and lowering of other inflammatory cytokines levels including TNF-α.
Taheri and colleagues’ review also highlighted a randomized control trial of patients suffering from a chronic joint disease. Osteoarthritis was reduced to half in study participants taking 1,340 mg of powdered extract of nettle leaves combined with 50 mg of diclofenac compared to those taking a standard dose of 200 mg diclofenac.
A 2019 review by Esposito and colleagues in Molecules focused on stinging nettle’s cancer chemopreventive potential. Their investigation included studies examining the cytotoxic, antitumor, and antimetastatic effects of U. dioica on several human cancers. They report that U. dioica may exert biological anticancer effects through various mechanisms of action, including antioxidant and antimutagenic properties, induction or inhibition of key processes in cellular metabolism, and the ability to activate the apoptotic pathways.
Daily requirements and dietary sources
Nettle is available as dried or freeze-dried leaf, extract, capsules, tablets, root tincture, juice, or tea. It’s also sold as an ointment or cream to be applied to the skin. As the supplement is not regulated by FDA, there is no standard dose available.
What to tell your patients
There is a wealth of scientific information about the benefits of stinging nettle, which is generally considered safe with occasional adverse effects including sweating, GI discomfort, and hives or rash (upon touching the plant or using a topical application). Advise pregnant or breastfeeding patients to avoid nettle. There is some evidence that patients with renal ailments, diabetes, or kidney issues as well as those taking ACE inhibitors, beta blockers, or calcium channel blockers should discuss nettle use with their health care provider as stinging nettle may lower blood pressure or raise or lower blood glucose. Possible contraindications include blood-thinning drugs, including warfarin, clopidogrel, and aspirin. ■