Nettles
Scientific Name(s): Urtica dioica L. Family: Urticaceae (nettles)
Common Name(s): Stinging nettle , nettle
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Uses of Nettles
Proven as a diuretic, nettles are also being investigated as treatment for hay fever and irrigation of the urinary tract.
Nettles Dosing
The herb is used as a diuretic at doses of 8 to 12 g/day. In contrast, the root is used for urinary conditions such as benign prostate hypertrophy at 4 to 6 g/day. 1
Contraindications
Contraindications have not yet been identified.
Pregnancy/Lactation
Documented adverse effects (reputed abortifacient and to affect menstrual cycle). Avoid use. 2
Nettles Interactions
None well documented.
Nettles Adverse Reactions
Internal side effects are rare and are allergic in nature. External side effects result from skin contact and take the form of burning and stinging that persist for 12 hours or more.
Toxicology
No major toxicities have been reported with nettles.
Botany
Nettles are perennial plants native to Europe and found throughout the US and parts of Canada. This plant has an erect stalk and can stand up to 3 feet. It has dark green serrated leaves that grow opposite each other along the stalk. The plant flowers from June to September. The leaves contain bristles that transmit irritating principles upon contact. The nettle fruit is a small, oval seed about 1 mm wide. It is yellow-brown in color. 3
History
This plant is known for its stinging properties. However, it has been used in traditional medicine as a diuretic, antispasmodic, expectorant and treatment for asthma. The juice has been purported to stimulate hair growth when applied to the scalp. Extracts of the leaves have been used topically for the treatment of rheumatic disorders. The tender tips of young nettles have been used as a cooked pot herb in salads.
Chemistry
More than 24 chemical components have been identified in nettles. The primary structure of Urtica dioica agglutinin has been determined and found to be a two-domain member of the hevein family of proteins. 4 Compounds isolated from the roots and flowers include scopoletin, steryl derivatives, lignan glucosides and flavonol glycosides. 5 Sixteen free amino acids have been found in the leaves. 6 Nine flavonoid compounds have been isolated and identified. 7 Phenylpropanes and lignans from the roots have been isolated and described. 8 The plant also contains vitamins C, B-group and K, along with other various acids. 3 Mineral salts have also been found. Nitrate concentrations in nettle leaves have been reported. 9 Glucokinin (allegedly responsible for “antidiabetic activity”) has been reported, but its presence in the plant is controversial. 3 In addition to sitosterol, at least six other related steroids have been identified. 10 The plant has been used as a commercial source of chlorophyll. The young shoots are rich in carotene and vitamin C. The stinging trichomes of nettle contain amines, such as histamine, serotonin and choline. Nettle fruit contains protein, mucilage and fixed oil. 3 Aqueous extracts of the plant have been studied. 11 , 12 , 13 , 14 Isolation and identification among nettles have been performed. 15 HPLC, GC and other methods have determined a specific lectin found only in Urtica dioica roots, which may help to standardize preparations. 16 , 17
Nettles Uses and Pharmacology
Nettle herb is known to have mainly diuretic actions. Nettle's purported claims against diabetes, cancer, eczema, rheumatism, hair loss and aging have been reported 18 , 19 but are probably related to its “age-old” roles in folk medicine. Other folk medicine applications include wound healing, treatment of scalp seborrhea and greasy hair, and gastric juice secretion. 3 A combination product includes nettle to treat hyposecretory gastritis. 20
DiureticAnimal data
Research reveals no animal data regarding the use of nettles as a diuretic.
Clinical dataTreatment over 14 days increases urine volume and decreases systolic blood pressure. 3
Bladder irrigant/Kidney stonesThe German Commission E Monograph supports this indication by its similar listing for “irrigation in inflammation of the urinary tract and in the prevention and treatment of kidney gravel.” 3 Nettle's use in expelling bile has been studied. 21
Animal dataResearch reveals no animal data regarding the use of nettles as a bladder irrigant or for kidney stones.
Clinical dataNettle in a combination product containing several other herbs has been tested in 22 patients for bladder irrigation. Post-operative blood loss, bacteriuria and inflammation were all reduced following prostatic adenomectomy. 22
Benign prostatic hyperplasiaA possible mechanism may be caused by a hydrophobic constituent (eg, steroidal), which inhibits the sodium-potassium ATP-ase activity of the prostate, leading to suppressed cell growth in this area. 23 Another report explains a different mechanism but suggests the aqueous extract is the active component in BPH therapy to inhibit the sex hormone-binding globulin to its receptor. 24
Animal dataResearch reveals no animal data regarding the use of nettles for benign prostatic hyperplasia.
Clinical dataUrtica dioica in a combined extract to treat benign prostatic hyperplasia (BPH) in 134 patients was effective in reducing urine flow, noctura and residual urine. A 300 mg dose of the plant extract was as effective as 150 mg. 25
Allergic rhinitisAnimal data
Research reveals no animal data regarding the use of nettles in allergic rhinitis.
Clinical dataFreeze-dried nettle has been evaluated for allergic rhinitis. In a double-blind trial, 57% of 69 hay fever sufferers who completed the trial judged the nettle preparations to be moderately to highly effective in treatment vs placebo. 26
Miscellaneous usesCNS depressant effects of nettle extract in rats are described, suggesting diminished motor activity and reduced convulsions, along with hypothermic effects with its use. 27
Reports on pharmacology in animals are available, including its dihydroergotamine-like effect on mouse uterine smooth muscle, probably caused by pyranocoumarin, 27 nettle's carbohydrate binding properties 28 and its ability in vitro to inhibit enzyme aromatase. 29 A lectin present in nettle was found to be a potent and selective inhibitor of HIV and cytomegalovirus replication in vitro . 30 When evaluated for its anti-diabetic effect, Urtica dioica slightly increased glycemia, aggravating the condition in two reports. 31 , 32
Dosage
The herb is used as a diuretic at doses of 8 to 12 g/day. In contrast, the root is used for urinary conditions such as benign prostate hypertrophy at 4 to 6 g/day. 1
Pregnancy/Lactation
Documented adverse effects (reputed abortifacient and to affect menstrual cycle). Avoid use. 2
Interactions
None well documented.
Adverse Reactions
Nettles are known primarily for their ability to induce topical irritation following contact with exposed skin. This contact urticaria is accompanied by a stinging sensation lasting 12 hours or longer. A report linked mast cells and dermal dendritic cells to this response. Immediate reaction to nettle stings is caused by histamine content, while the persistence of the sting may be caused by other substances directly toxic to nerves. 33
The stinging hairs of the nettle plant comprise a fine capillary tube, a bladder-like base filled with the chemical irritant and a minute spherical tip, which breaks off on contact leaving a sharp-pointed tip that penetrates the skin. The irritants are forced into the skin as the hair bends and constricts the bladder at the base.
The topical irritation is treated by gently washing the affected area with mild soapy water. Treatment with systemic antihistamines and topical steroids may be of benefit. Other side effects of nettle are rare but include allergic effects such as edema, oliguria and gastric irritation. 3
Toxicology
No major toxicities have been reported with nettles.
Bibliography
1. Gruenwald J, ed. PDR for Herbal Medicines . 2nd ed. Montvale, NJ: Thomson Medical Economics; 2000: 729-733.2. Newall CA, Anderson LA, Phillipson JD, eds. Herbal Medicines: A Guide for Health-Care Professionals . London: Pharmaceutical Press; 1996.
3. Bisset N. Herbal Drugs and Phytopharmaceuticals , CRC Press, Stuttgart, Germay 1994;502–7.
4. Beintema J, et al. FEBS Letters 1992;299(2):131–4.
5. Chaurasia N, et al. Deutsche Apotheker Zeitung 1986;126(Jan 16):81–3.
6. Adamski R, et al. Herba Polonica 1984;30(1):17–26.
7. Ellnain-Wojtaszek M, et al. Herba Polonica 1986;32(3–4):131–7.
8. Chaurasia N, et al. Deutsche Apotheker Zeitung 1986;126(Jul 17):1559–63.
9. Peura P, et al. ACTA Pharmaceutica Fennica 1985;94(2):67–70.
10. Chaurasia N,et al. Journal of Natural Products 1987;50(Sep-Oct):881–5.
11. Bakke I, et al. Meddelelser Fra Norsk Farmaceutisk Selskap 1978;40(3):181–8.
12. Muraviev I, et al. Farmatsiia 1986;35(6):17–20.
13. Beck E. Deutsche Apotheker Zeitung 1989;129(Oct 12):2169–72.
14. Wagner H, et al. Planta Medica 1989;55(5):452–4.
15. Shomakers J, et al. Deutsche Apotheker Zeitung 1995;135(Feb 16):40–44, 46.
16. Schilcher H, et al. Deutsche Apotheker Zeitung 1986;126(Jan 16):79–81.
17. Willer F, et al. Deutsche Apotheker Zeitung 1991;131(Jun 13):1217–21.
18. Atasu E, et al. Farmasotik Bilimler Dergisi 1984;9(2):73–81.
19. Wichtl M. Deutsche Apotheker Zeitung 1992;132(Jul 23):1569–76.
20. Krivenko V, et al. Vrachebnoe Delo 1989;(3):76–8.
21. Rossiiskaya G, et al. Farmatsiia 1985;34(1):38–41.
22. Davidov M, et al. Urologiia I Nefrologiia 1995;(5):19–20.
23. Hirano T, et al. Planta Medica 1994;60(1):30–3.
24. Hryb D, et al. Planta Medica 1995;61(1):31–2.
25. Krzeski T, et al. Clinical Therapeutics 1993;15(6):1011–20.
26. Mittman P. Planta Medica 1990;56(1):44–7.
27. Broncano F, et al. Anales De La Real Academia De Farmacia 1987;53(1):69–75.
28. Shibuya N, et al. Archives of Biochemistry & Biophysics 1986;249(1):215–24.
29. Gansser D, et al. Planta Medica 1995;61(2):138–40.
30. Balzarini J, et al. Antiviral Research 1992;l18(2):191–207.
31. Swanston-Flatt S, et al. Diabetes Research 1989;10(2):69–73.
32. Roman R, et al. Archives of Medical Research 1992;23(1):59–64.
33. Oliver F, et al. Clinical & Experimental Dermatology 1991;16(1):1–7.
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