Urtica dioica

Botanical Name: Urtica dioica, Urticaceae

Botanical synonyms: U. gracilis, U. lyallii.

Common names: Nettle, Stinging Nettle.

Similar species: U. urens (Dog Nettle)

Plant description: Nettle is a long-lived herbaceous perennial, dull-green in color when mature, 25-150 cm in height, armed with minute prickles on the stem and under the leaves that release anacrid, skin-irritating juice when pressed or broken. The stem is 4-angled and branching, arising from a creeping and branching rhizome. The leaves are opposite, 3.5-12 cm in length, lance-shaped to ovate, the base cordate and the tips acuminate, the argins coarsely and acutely serrate. The small green flowers bloom during summer, and can be either monoecious or dioecious, arranged in branching, axillary spikes up to 10 cm long. The fruit is an achene, green, 1-1.25 mm long. U. urens is a much smaller, tap-rooted annual.

Habitat, ecology and distribution: Found throughout temperate North America and Europe, in meadows and thickets, and along stream banks and in open forests. Nettle is generally considered to be an old world species, and despite being commonly associated with white people, there are several references to its usage by First Nations people in the ethnobotanical literature. Nettle is often found growing in large colonies in disturbed areas, in abandoned pastures, avalanche tracks, or along roadsides, always in rich moist soil.

Part used: leaf, root, seed.

History: Nettle has a long history of use all over the world as a food, medicine and textile fiber. Weiss properly calls Nettle a ruderale, meaning that it tends to grow around human settlements (1988, 261). Grieve states that the common name of Nettle is derived from the German noedl meaning ‘needle,’ possibly from its sharp sting, or in reference to the fact that it once furnished thread and cloth before the introduction of flax and hemp into Europe (1971, 575). ‘Net’ is stated as being the passive participle of ne, a verb that in many Indo-European languages such as Latin and Sanskrit, means ‘sew’ or ‘bind,’ respectively (Grieve 1971, 575). Nettle was at one time highly esteemed as a textile fiber, and is highly durable, once thought to be the only real equivalent to cotton, used by the third Reich during the second world war as a textile in manufacture of German I uniforms (Grieve 1971, 575; Wood 1999, 482). Beyond its importance as a fiber however, Nettle has long been regarded as an important and nutritious green vegetable, one of the first edible green growing things of spring, picked young and eaten steamed or in soups, said to be a good corrector of the bowels. The body of the famous Tibetan yogi Milarepa is said to have turned green from consuming nothing other than Nettle during his meditations. Despite being classified as a weed in many parts of the North America, Nettle was at one time highly prized commodity in rural areas, where the English poet Campbell recounts of his travels, “In Scotland I have eaten nettles, I have slept in nettle sheets, and I have dined off a nettle tablecloth” (Grieve 1971 575). More recently Nettle has been used as a commercial source of chlorophyll, and Weiss states that this color has been used in Germany as a food coloring agent for canned vegetables (1988, 262; Mills and Bone 2000, 490).

Constituents: The constituent profile of Nettle is said to vary depending upon the plant part. As far as the roots are concerned, the principle chemicals of interest are the sterols and steryl glycosides, including beta-sitosterol. Nettle root also contains lignans (e.g. secoisolariciresinol) and six isolectins collectively referred to as UDA (Urtica dioica agglutinin). Other constituents in the root include phenylpropanes, polyphenols, polysaccharides, tannins and the coumarin scopoletin. The fresh leaf contains a similar range of constituents, with smaller amounts of plant sterols, but proportionally higher levels of flavonol glycosides such as quercitin, as well as carotenoids, chlorophyll, acids (e.g. carbonic and formic acid), vitamins (C, B, and K) and minerals (e.g. calcium, magnesium, and potassium). The stinging trichomes are stated be fashioned primarily from silica, and contain a mixture including formic acid, acetylcholine, histamine and serotonin. There is no data for constituents in the seeds, although the flowers are also stated to possess scopoletin (Mills and Bone 2000, 491; Bergner 1997, 245; Newall et al 1996, 201; Weiss 1988, 261).

Medical Research:
• Benign prostatic hypertrophy (BPH): There have been several clinical trials that have demonstrated the efficacy of Nettle in BPH. Mills and Bone describe a series of uncontrolled clinical trials in Europe that began as early as 1979 that demonstrated improvements in urological symptoms in BPH patients (2000, 494). In 1984 a large observational trial in Germany conducted on 4051 patients with BPH, Nettle root extract was shown to improve symptoms such as nocturia (Mills and Bone 2000, 494). More recently Nettle root has undergone a series of double blind, placebo-controlled clinical trials. In two clinical trials conducted in 2000 and 1997, a subgroup of 431 patients and another group of 543 patients with early stage BPH were analyzed in a randomized, multicentre, double-blind clinical trial. Patients received a fixed combination of extracts of Saw Palmetto fruit (Serenoa repens) and Nettle root (Urtica dioica), the synthetic 5-alpha-reductase inhibitor finasteride, or placebo. The herbal extract was shown to exhibit an activity similar to finasteride, but with significantly less adverse reactions, including significantly fewer cases of diminished ejaculation volume, erectile dysfunction and headache (Sokeland 2000; Sokeland and Albrecht 1997). In another double-blind placebo-controlled trial of 40 BPH patients 1200 mg of a 5:1 Nettle root extract given on a daily basis was shown to decrease urinary frequency and serum levels of SHBG (Mills and Bone 2000, 494). In a clinical trial in Poland 134 patients with symptoms of BPH were randomly assigned to receive two capsules of the standard dose of an Urtica and Pygeum preparation (300 mg of Urtica dioica root extract combined with 25 mg of Pygeum africanum bark extract), or two capsules containing half the standard dose, twice daily for 8 weeks. After 28 days of treatment, urine flow, residual urine, and nycturia were significantly reduced in both treatment groups. After 56 days of treatment, further significant decreases were found in residual urine (half-dose group) and in nocturia (both groups) (Krzeski et al 1993).
• Inflammatory joint disease: In a group of eighteen patients with joint pain treated with the topical use of Nettle sting all except one respondent were sure that the therapy had been very helpful and several considered themselves cured. No observed side effects were reported, except a transient urticarial rash (Randall et al 1999). An extract of Urtica dioica leaf was investigated with respect to effects of the extract on the lipopolysaccharide (LPS) stimulated secretion of proinflammatory cytokines in human whole blood of healthy volunteers. The resultant rise in tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) secretion after LPS administration was significantly reduced by the Urtica extract in a dose dependent manner. Isolated constituents including phenol carbon acid derivates and flavonodes such as caffeic malic acid, caffeic acid, chlorogenic acid, quercetin and rutin did not influence LPS stimulated TNF-alpha, IL-1 beta and IL-6 secretion in tested concentrations (Obertreis et al 1996). In an open multicenter clinical trial of 219 patients with arthritis Nettle leaf was compared against NSAID therapy, demonstrating a similar reduction in pain and immobility, with excellent tolerability. In an open randomized trial of 37 patients with acute arthritis, 50 g of stewed Nettle leaf consumed on a daily combined with 50 mg of diclofenac was shown to be as effective as the full 200 mg dose of diclofenac in the treatment of symptoms, over a 2 week period (Mills and Bone 2000, 495).
• Allergic rhinitis: In a double-blind placebo-controlled randomized study of 98 patients with allergic rhinits the effect of a freeze-dried preparation of Urtica dioica was compared against placebo. Based on daily symptom diaries and the global response recorded at the follow-up visit after one week of therapy, Urtica dioica was rated higher than placebo in relieving symptoms (Mittman 1990).

Toxicity: The LD50 of a Nettle leaf infusion in rats given by gavage was determined to be 1.31g/kg. There are reports in the literature of gastric irritation and skin irritation associated with a Nettle infusion. An extract of the root is reported to have promoted mild digestive upset in one clinical trial. The stinging hairs are well known to promote a characteristic urticaria in exposed skin (Mills and Bone 2000, 496; Newall et al 1996, 201).

Herbal action: nutritive, alterative, antirheumatic, antiallergenic, hemostatic, uterine tonic (leaf); prostatic decongestant, pelvic decongestant (root); kidney trophorestorative (seed)

Indications: anemia, weakness, nutrient deficiency, chronic urticaria, eczema, psoriasis, respiratory catarrh, bronchitis, asthma, hayfever, arthritis, osteoarthritis, inflammatory joint disease, muscle and joint injuries, menorrhagia, bladder irritability, urolithiasis, nephritis, chronic renal failure; dried plant ointments and salves topically in wounds and burns, fresh plant topically in arthritis

Contraindications and cautions: known hypersensitivities

Medicinal uses: Nettle leaf is among our most valuable herbal remedies, not because it is exceptionally potent or fast-acting, but because it is none of these things: it is a slowly acting nutritive herb that gently cleanses the body of metabolic wastes. Nettle leaf is thus one of the safest and happiest of the alteratives, especially in the treatment of chronic disorders that require long term treatment. This activity of Nettle leaf is perhaps best utilized as a kind of herbal food, eaten as a green vegetable, spice, condiment, or drunk in generous amounts as a herbal infusion. Taken in such a way Nettle is highly reputed in the treatment of chronic metabolic disorders, providing a gentle stimulant effect upon the lymphatic system, seeming to enhance the excretion of wastes through the kidneys.  Weiss suggests that Nettle acts similarly to Dandelion leaf, promoting the elimination of uric acid from joints with a gentle, alkalizing diuretic activity. Nettle is thus indicated in most kinds of joint diseases, and doubly so in degenerative conditions, not only for its ability to arrest inflammatory states and enhance the excretion of wastes, but due to its high nutrient content, especially in the minerals calcium and magnesium required for bone-remodelling. Nettle leaf is also an exceptionally useful plant to correct symptoms of gastrointestinal excess, such as hyperchlorhydria with sour eructations and nausea, chronic diarrhoea, and mucus colitis. Similarly, the styptic properties of both Nettle leaf and root make it useful in infectious diarrheas, bloody diarrheas and in bleeding hemorrhoids, although it cannot be considered as an emergency remedy. Felter and Lloyd recommend a syrup made from Nettle root with Wild Cherry bark (Prunus virginiana) and Blackberry root (Rubus villosus) as a general remedy in summer diarrhea in both children and adults (1893). As a nutritive agent, Nettle is very much esteemed in the treatment of anemia and asthenic states generally, especially inwomen, appearing to promote the process of protein transanimation in the liver, effectively utilizing digested proteins, while simultaneously preventing them from being discharged through the body as waste products (Wood 1999, 481). For this reason Nettle, as well as in its role as a gentle uterine tonic, is a highly valued beverage during pregnancy and post-partum to enhance milk production. In the treatment of hayfever, the freeze-dried encapsulated herb is generally thought to be best, two capsules taken every 5 minutes until symptoms have diminished. Cook considered the root to be “…a strong astringent, with moderately stimulating and tonic qualities,” indicating its usefulness in bleeding of the nose, lungs, stomach, bowels and in passive menorrhagia (1869). More recently, the root has undergone a significant degree of investigation in the treatment of prostatic congestion. A combined analysis of its traditional uses and demonstrated activities in clinical trials suggests that the root is a good pelvic decongestant, justifying its usage in any condition that is affected by such a state, including hemorrhoids, passive menorrhagia, fibroids and dysmenorrhea. Topically the leaves are considered to be a useful styptic in wounds, and when the whole plant is picked fresh and thrashed on arthritic joints they will promote an urticaria that indicates a profound rubifacient property that will eventually leave the treated joint very much relieved, and by some accounts, is a cure. The seeds were used by the Eclectic physicians as a remedy for goiter and in parasitic diseases. Equally the seeds appeared to figure importantly in obstinate skin conditions and in renal disease, a use that has been more recently confirmed by respected Cherokee herbalist David Winston. Nettle leaf can be considered a good remedy for chronic urinary irritation, and the seeds in nephritis and chronic renal failure. Ground into a powder and combined with a little sea salt and ground sesame seed, the addition of Nettle seed is a tasty and healthy variation on gomashio, a popular Japanese condiment.

Pharmacy and dosage:
Fresh Plant Tincture: leaf or root, 1:2, 95% alcohol, 3-60 gtt
Dry Plant Tincture: leaf, root or seed, 1:3 or 1:5, 25-40% alcohol, 3-60 gtt, 1-15 mL
Hot Infusion: 1:20, leaf, up to 1 liter daily
Powder: leaf 8-12 g; root 6-8 g