Food as Medicine: Stinging Nettle (Urtica dioica, Urticaceae)
Urtica dioica (Urticaceae) is commonly known as nettle, common nettle, or stinging nettle. The species is an herbaceous perennial with a spreading growth habit. Growing 4-6 feet tall, stinging nettle produces numerous erect and wiry stems that hold up its opposite, roughly textured, serrated leaves.1-4 It produces small, inconspicuous greenish-brownish flowers that emerge as axillary inflorescences.2 The stems and undersides of leaves are covered with hairs called trichomes. When touched, these stinging trichomes inject a chemical cocktail that typically causes localized skin irritation as well as a painful, tingling sting from which the species has derived its most common name, stinging nettle.1,5
The Urticaceae family contains about 500 known species, distributed mainly in tropical areas.1 The genus Urtica, whose name comes from the Latin uro (to burn) and urere (to sting), consists of both annual and perennial herbaceous plants known for the burning properties of the stinging hairs of their leaves and stems.1,2,6 (Nettle is the Anglo-Saxon word for “needle.”) Urtica urentissima, a species found in Java, produces burning effects that can last an entire year and reportedly can even cause death. Urtica dioica is, comparatively, a more docile species that has a long history of use as a food and medicine.1,2,7 It is widely distributed in temperate climates of Europe, Asia, northern Africa, and North America.1 In North America, U. dioica has become naturalized in every state except Hawaii.1 There are at least six subspecies of U. dioica, some of which formerly were classified as separate Urtica species. Urtica dioica subsp. galeopsifoliais the only one of the six subspecies that does not have stinging hairs.1
Phytochemicals and Constituents
Stinging nettle is a perennial edible whose leaves are a relatively good source of caloric energy, protein, fiber, and an array of health-promoting bioactive compounds.7 These include vitamins A, C, and K; fatty acids (α-linoleic acid and linoleic acid); and minerals including iron, manganese, potassium, and calcium.2,7,8 Notably, stinging nettle leaves contain nine carotenoids, including lutein and lutein isomers, β-carotene, and β-carotene isomers.2 Other phytochemicals in nettle leaf include B vitamins, vitamin E, coumarins, flavonoids, phenolic acids, tannins, organic acids, water-soluble silicates, and chlorophyll.8,9 The therapeutic benefit of stinging nettle is attributed to its abundant phenolic compound content, which includes caffeic acid, ferulic acid, esculetin, scopoletin, kaempferol, quercetin, quercitrin, rutin, and glycoproteins.2 Stinging nettle leaves can be cooked like spinach (Spinacia oleracea, Chenopodiaceae) and are safe for consumption, as heat deactivates the stinging compounds.10 Nettle leaf has higher levels of all essential amino acids, except leucine and lysine than spinach.11
When harvested at a length of four to six inches, young nettle leaves are most tender, stingless, and are higher in iron and manganese than mature leaves.5 However, nettle plants that are two years old or more contain higher levels of chlorophyll and carotenoids than younger plants. Young leaves harvested in early spring also can be dried for use in teas, soups, and baked goods. Nettle leaf retains a significant portion of vitamins, minerals, and essential nutrients even after leaves are blanched or cooked/boiled prior to freezer storage. To prepare a nettle infusion that retains the highest level of vitamin C, a study confirmed that the most efficient steeping time is 10 minutes at a temperature of 140°F (60°C).8 Further consideration should be given to the processing and selling of stinging nettle leaf as a functional and nutritive food.
Historical and Commercial Uses
Some consider stinging nettle a bothersome weed, but its long history of use tells a different story. Stinging nettle has been used as a source of fiber (stem), dye (leaf and rhizome), food/fodder (leaf), and medicine (leaf, rhizome/root, and seed).2,8
Since ancient times, stinging nettle has been used as a fiber crop substitute for flax (Linum usitatissimum, Linaceae). In Denmark, burial shrouds made from nettle fiber were discovered that date back to the Bronze Age (3000–2000 BCE). Early Europeans and indigenous Americans used the strong nettle fiber to make sailcloth, sackcloth, cordage/rope, and fishing nets.1 In Scotland, nettle stalk was cultivated for fiber and also used for small-scale papermaking. Nettle fiber also was used during both World Wars when other crops like cotton (Gossypium hirsutum, Malvaceae) were scarce. Stinging nettle fiber has a cellulose content similar to that of flax and hemp (Cannabis spp., Cannabaceae), and it is much stronger than both flax and cotton while being comparable in strength to ramie (Boehmeria nivea, Urticaceae) fiber.12
In periods of food shortage during both World Wars, stinging nettle was used fresh, dried, milled, or as silage for feeding poultry, cattle, horses, and pigs.12 Ranchers used nettle in livestock feed as a nutritious way to supplement the animals’ diets. By adding stinging nettle leaf into poultry feed, vitamin A intake increased by about 60-70% and protein intake by about 15-20%, reducing overall feeding requirements by about 30%. Hens supplemented with nettle feed typically lay eggs with brighter yellow carotenoid-rich yolks.12
Considered a nutritive food and medicine for thousands of years among numerous cultures, stinging nettle leaves have been used traditionally for scurvy, anemia, arthritis, seasonal allergies, wound healing, and general fatigue, and as a diuretic and to stimulate pancreatic secretion.1,9 Stinging nettle tea has been used historically as a cleansing spring tonic and blood purifier.1,3 The juice of nettle leaf has been used as a hair rinse to control dandruff and to stimulate hair growth and is a functional ingredient in modern European hair-care formulations. It is used as a vegetarian source of rennet in cheese-making and is still included among Passover herbs.1
Nettle leaf has been used safely in large food-like doses (up to 100g daily) for thousands of years.5 Ancient Egyptians reportedly used nettle infusions to relieve arthritis and lower back pain.7 Hippocrates (460-ca. 377 BCE) and other early Greek physicians used nettle for more than 60 ailments. In the first and second centuries CE, Greek physicians Dioscorides and Galen reported the use of stinging nettle leaf for its diuretic and laxative properties and for the treatment of asthma, pleurisy, and spleen illnesses.3 The 16th-century herbalist John Gerard used nettle leaf as an antidote for poison.1 In the 19th century, the classification of stinging nettle as a diuretic was documented in Greek medical literature.5
It is thought that nettle leaf’s high chlorophyll content gives it detoxifying and anti-infective properties. In his 2nd-century book De Simplicibus Medicaminibus, Galen recommended nettle for dog bites, gangrenous wounds, swellings, nosebleeds, mouth sores, and tinea (fungal infections caused by ringworm). Seventeenth-century English herbalist Nicholas Culpeper recommended a nettle-honey preparation for wounds and skin infections, worms in children, as an antidote to venomous stings, and as a gargle for throat and mouth infections, .1 Modern research on chlorophyll indicates that it has some detoxifying, anti-carcinogenic properties and may ameliorate the side effects of some drugs.2 Nettle leaves also are used as a source of chlorophyll for commercial supplements.13Additionally, nettle’s vitamin K-rich leaves were powdered and used as a styptic for nosebleeds and used internally for excessive menstruation, and internal bleeding.1,3
The season for nettle leaf medicine is spring when it traditionally is harvested and used fresh or dried for its ability to deliver bountiful nutrients.1 Many North American tribes consider nettle tea safe and appropriate to use as a gynecological aid for those with anemia or malnourishment.1
Stinging nettle is a very popular wild edible plant (WEP) in several developing countries, where it is used in soups, curries, or as a cooked vegetable. Vinegar or lemon (Citrus limon, Rutaceae) juice often is added to cooked nettle preparations to improve flavor and enhance mineral absorption.14 In the Caucasus country of Georgia, a meal of boiled nettle greens seasoned with walnuts (Juglans spp., Juglandaceae) is common. In many cases, these WEPs contribute to community food security and, potentially, to local economies.7
Nettle leaf powder/flour has been incorporated into breads and pastas and is used as a protein-rich supplement in starchy diets. In one analysis, the protein content of ground wheat (Triticum aestivum, Poaceae), barley (Hordeum vulgare, Poaceae), and stinging nettle was found to be 10.6%, 11.8%, and 33.8%, respectively, indicating that the nettle powder contained about three times more protein per serving than the cereal crops. 7
A low-carbohydrate, high-fiber diet can support good digestive health. Nettle powder has low carbohydrate content with high levels of protein, minerals, fat, and fiber. Nettle powder is considered a low-glycemic food. Whole grains alone can provide much-needed fiber to the diet. However, grain products enriched with nettle powder can provide extra fiber, in addition to an array of healthful nutrients. When combining nettle powder with barley flour into items like biscuits, noodles, and breakfast cereals, the protein, mineral, fiber, and bioactive compound content increased while overall caloric value decreased, according to an analysis. 7
A practice called “urtification” is perhaps the most ancient medicinal use of the plant. In this process, fresh nettle, with its stinging compounds, was applied externally as a rubefacient to stimulate circulation and bring warmth to joints and extremities of paralytic, rheumatic, or stiff limbs.5,7 This induced, localized irritation stimulates an immune response and pain relief after the stinging subsides. This was considered standard practice for treating chronic rheumatism, lethargy, coma, paralysis, and even typhus and cholera.1,5 Ironically, nettle leaves often were prepared as syrup or tincture to treat urticaria, or the rash they produce upon contact with the skin.1
The root of stinging nettle is a rich source of phytosterols and has been used to reduce prostate gland inflammation and to treat rheumatic gout, nettle rash, and chickenpox.3,10 In 1986, the German Commission E approved the use of stinging nettle root, taken orally, as a nonprescription medicine to treat urinary difficulties associated with stages I and II of Benign Prostatic Hyperplasia (BPH).14,15 The European Medicines Agency’s 2012 monograph on nettle root indicates its safe use to relieve lower urinary tract symptoms (LUTS) related to BPH.16
Based on published evidence, U. dioica and its phytoconstituents have both hypoglycemic and anti-inflammatory activities.3 Nettle leaf, whether used orally or topically, has been shown to be able to inhibit pro-inflammatory enzymes.2 This indicates that nettle leaf may be a potential aid in treating chronic, inflammatory disease processes. Promising evidence suggests that nettle can help control inflammation associated with diabetes mellitus, rheumatoid and osteoarthritis, allergic rhinitis (hay fever), and BPH.12
Type 2 diabetes mellitus has become one of the most common preventable diseases globally. Hyperglycemia, the relative or absolute deficiency of insulin at the cellular level, is one of the predisposing factors for oxidative stress in the body.17 Oxidative stress — often indicated by elevated levels of low-density lipoprotein (LDL) cholesterol and glutamic pyruvic transaminase (SGPT), and low levels of nitric oxide — increases the incidence of cardiovascular risk factors and contributes to diabetic macro- and microvascular complications. Moreover, high blood glucose causes fat deposits in the liver. Stinging nettle leaf extracts have demonstrated natriuretic (stimulating sodium excretion via urine), diuretic, and hypotensive effects. Nettle leaf offers a therapeutic dietary option for patients with digestive and kidney diseases or injuries after renal transplantation, as well as those with diabetes.2
Stinging nettle leaf extract acts on the pancreas to increase insulin secretion by the Islets of Langerhans and has an inhibitory effect on alpha-glucosidase. Theoretically, stinging nettle leaf extract’s polyphenols may protect beta cells in the pancreas and stabilize lipid peroxidation.17 Its effects on blood pressure are tied directly to stinging nettle’s ability to increase serum nitric oxide levels, which opens potassium channels and has relaxant effects on blood vessel walls.
A 2015 clinical study found that supplementation with U. dioica hydroethanolic aerial parts extract for eight weeks helped improve markers of cardiovascular disease and oxidative stress in diabetic patients.17 At the end of the study, participants in the nettle extract group experienced a statistically significant reduction in fasting blood glucose, lower triglyceride levels, increased high-density lipoprotein (HDL) cholesterol levels, decreased SGPT levels, increased nitric oxide levels, and increased superoxide dismutase (SOD) over baseline, indicating an overall reduction in oxidative stress. The only change in the placebo group was an increase in triglyceride levels. Researchers suggest these results encourage the use of U. dioica as an additional therapy in those with type 2 diabetes.
Rheumatoid Arthritis and Osteoarthritis
According to the US Centers for Disease Control and Prevention (CDC), the most common form of arthritis is osteoarthritis. Other common rheumatic conditions include gout, fibromyalgia, and rheumatoid arthritis.18 In clinical trials that tested the effectiveness of nettle extract or capsules against the common NSAID diclofenac for the treatment of rheumatoid arthritis, osteoarthritis and fibromyalgia, stinging nettle preparations alone provided moderate pain relief and had fewer side effects than diclofenac.5 The use of stinging nettle in addition to diclofenac provided the greatest amount of pain relief, and subjects used lower doses of diclofenac to achieve pain relief.
The use of fresh nettle topically to control pain and inflammation works in the same manner as topical capsaicin cream: the histamine released upon contact causes a counterirritant effect resulting in localized irritation that blocks afferent sensory nerves from carrying pain signals away from the area of urtication.5,19Three different clinical trials have investigated topical nettle leaf application for the treatment of pain associated with osteoarthritis. Participants in these trials reported a significant reduction in pain as well as the use of NSAIDs for pain management.5 Other studies have investigated pain relief with a cream from a stinging nettle extract in an oil-in-water emulsion, a more practical way to integrate modified “urtification” treatment in a clinical setting.19
One small clinical study with 23 osteoarthritis patients used nettle cream topically twice daily for two weeks. After the study concluded, not only was there a mean reduction in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores for those using the stinging nettle leaf cream, but many of the participants requested continuance of the nettle cream treatment to alleviate pain and improve physical function.19
Allergic rhinitis, or seasonal allergies, is a major risk factor for developing asthma.20 Common over-the-counter (OTC) drugs for seasonal allergy symptoms often are associated with adverse side effects, including drowsiness, dry mouth, and headache. Freeze-dried stinging nettle leaves have been used to treat symptoms of allergic rhinitis. Freezing the fresh leaves or their extracts preserves the bioactive amines including histamine and acetylcholine.5 Nettle leaf prevents the release of pro-inflammatory mediators that cause allergic symptoms such as sneezing, nasal congestion, or itchy, watery eyes.2
In a clinical trial, patients with seasonal allergies received 300 mg of freeze-dried stinging nettle root extract daily for one week. Subjects in this trial rated the nettle preparation’s effectiveness higher than placebo and previous allergy medications.5 However, outcomes of a 2017 clinical trial using freeze-dried nettle root (a proprietary product commercially known as Urtidin [Barij Essence Pharmaceutical Co.; Kashan, Iran]) for seasonal allergy relief showed only a small improvement in the treatment group, who received Urtidin (one 150-mg tablet given four times daily; 600mg total) in addition to 10 mg loratadine (a common antihistamine) and nasal saline rinses over a one-month period.20 Despite the safety profile and low toxicity associated with the use of freeze-dried nettle root, additional, higher quality clinical trials are needed to further assess the efficacy of freeze-dried nettle preparations to relieve symptoms associated with seasonal allergies.
Benign Prostatic Hyperplasia
BPH is a common condition that occurs in aging men and eventually leads to LUTS, such as pain and difficulty with urination, urine storage, and post-urination (post-micturition) symptoms including dribbling and feeling of incomplete emptying.21 Standard medical treatments for LUTS include α1-blockers and 5α-reductase inhibitors, but both have undesirable side effects (postural hypotension and sexual dysfunction, respectively).
There is growing evidence that stinging nettle root is a safe and effective treatment for BPH.21 A 2016 meta-analysis of the clinical use of stinging nettle root extract for LUTS and BPH confirm that daily doses of 300-600 mg of stinging nettle root were superior to active controls (i.e., α1-blocker and 5α-reductase inhibitor pharmaceutical drugs). No randomized controlled trials evaluated reported any serious adverse side effects in patients who received stinging nettle root extract.
The use of stinging nettle leaf as a vegetable poses some challenges. The main challenge is urticaria: the immediate burning, stinging sensation upon contact with nettle leaves, which is followed by a short-lived, blanching rash.4 Those harvesting fresh nettle leaves must be cautious and avoid direct skin contact by wearing long sleeves and gloves. Once harvested, leaves should be cooked or steamed for 10-15 minutes before ingesting to deactivate nettle’s stinging compounds.14 The mechanism of action behind nettle’s sting is both biochemical and mechanical. Biochemically, nettle hairs release histamine, serotonin, acetylcholine, and leukotrienes B4 and C4. Mechanical irritation is induced when some of the trichomes remain in the skin after contact with the stems or leaves.4 For fresh nettle rash or stings, a poultice of the leaves of dock (Rumex spp., Polygonaceae), which generally grows near nettle patches, is a traditional remedy.1
An additional concern is the plant’s ability to bioaccumulate minerals like chromium, as well as heavy metals like arsenic and lead.22 Nettle patches are common on farmlands and orchards where soils may have been treated by agricultural pollutants, which make them contaminated substrates for plants like stinging nettle. Studies on stinging nettle leaf grown in contaminated orchard soils indicated significantly higher concentrations of arsenic and lead than those harvested from wild stands. Based on these findings, soils need to be tested for heavy metals and other contaminants prior to commercial cultivation and production of stinging nettle leaves. This will help to ensure stinging nettle grown for food and medicine maintains its quality and safety.
Macronutrient Profile: (Per 1 cup stinging nettle leaves, blanched [approx. 89 grams])
2.4 g protein
6.7 g carbohydrate
0.1 g fat
Secondary Metabolites: (Per 1 cup stinging nettle leaves, blanched [approx. 89 grams])
Excellent source of:
Vitamin K: 443.8 mcg (369.8% DV)
Vitamin C: 243 mg (270% DV)
Vitamin A: 1790 IU (35.8% DV)
Calcium: 428 mg (32.9% DV)
Manganese: 0.7 mg (30.4% DV)
Dietary Fiber: 6.1 g (20.3% DV)
Very good source of:
Magnesium: 51 mg (12.1% DV)
Riboflavin: 0.14 mg (10.8% DV)
Iron: 1.5 mg (8.3% DV)
Potassium: 297 mg (6.3% DV)
Vitamin B6: 0.09 mg (5.3% DV)
Phosphorus: 63 mg (5% DV)
Folate: 14 mcg (3.5% DV)
Niacin: 0.35 mg (2.2% DV)
Thiamin: 0.01 mg (0.8% DV)
DV = Daily Value as established by the US Food and Drug Administration, based on a 2,000-calorie diet.
|Recipe: Stinging Nettle Spanakopita
Adapted from Jen Farr24
Wear gloves while handling raw, fresh nettle leaves and stems. Wash leaves in cool water, then dry thoroughly. Check the source website for a photo tutorial on preparing the phyllo packets.
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- Ahmed M, Parsuraman. Urtica dioica, (Urticaceae): A stinging nettle. Sys Rev Pharm.2014;5(1):6-8.
- Baumgardner D. Stinging nettle: the bad, the good, the unknown. Journal of Patient-Centered Research and Reviews. 2016;3(1):48-53.
- Upton R. Stinging nettles leaf (Urtica dioica L.): Extraordinary vegetable medicine. Journal of Herbal Medicine. 2013;3: 9-38.
- Joshi BC, Mukhija M, Kalia AN. Pharmacognostical review of Urtica dioica L. International Journal of Green Pharmacy. 2014;201-209.
- Adhikari BM, Bajracharya A, Shrestha AK. Comparison of nutritional properties of stinging nettle (Urtica dioica) flour with wheat and barley flours. Food Science & Nutrition. 2016; 4(1):119-124.
- Wolska J, Czop M, Jakubczyk k, Janda K. Influence of temperature and brewing time of nettle (Urtica dioica, L.) infusions on vitamin C content. Rocz Panstw Zakl Hig. 2016;67(4):367-371.
- Lichius JJ, Hiller K, Loew D. Urticae folium, Urticae herba. In: Blaschek W, ed. Wichtl – Teedrogen und Phytopharmaka. Stuttgart, Germany: Wissenschaftliche Verlagsgesellschaft mbH; 2016:666-668.
- Van Wyk BE. Food Plants of the World. Portland, OR: Timber Press, Inc.; 2005:372.
- Rutto LK, Xu Y, Ramirez E, Brandt M. Mineral properties and dietary value of raw and processed stinging nettle (Urtica dioica L.). International Journal of Food Science. 2013;23:1-9.
- Di Virgilio N, Papazoglou EG, Jankauskiene Z, Di Lonardo S, Praczyk M, Wielgusz K. The potential of stinging nettle (Urtica dioica L.) as a crop with multiple uses. Industrial Crops and Products. 2015;68:42-49.
- Nettles. Drugs.com website. March 8, 2018. Available at: www.drugs.com/npp/nettles.html. Accessed July 9, 2018.
- Thorne Research. Urtica dioica; Urtica urens (Nettle) monograph. Alternative Medicine Review. 2007;12(3):280-284.
- Blumenthal M, Busse WR, Goldberg A, et al, eds. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin, TX: American Botanical Council; Boston, MA: Integrative Medicine Publishing; 1998.
- European Medicines Agency. Community herbal monograph on Urtica dioica L., Urtica urens L., their hybrids or their mixtures, radix. Published September 24, 2012. Available at: www.ema.europa.eu/docs/en_GB/document_library/Herbal_-_Community_herbal_monograph/2012/11/WC500134486.pdf.Accessed on May 15, 2018.
- Behzadi AA, Kalalian-Moghaddam, Ahmadi AH. Effects of Urtica dioica supplementation on blood lipids, hepatic enzymes enzymes and nitric oxide levels in type 2 diabetic patients: A double blind, randomized clinical trial. Avicenna Journal of Phytomedcine. 2015;6(6):686-695.
- Arthritis-related statistics. Center for Disease Control and Prevention website. January 11, 2018. Available at: www.cdc.gov/arthritis/data_statistics/arthritis-related-stats.htm. Accessed on May 15, 2018.
- Rayburn K, Fleischbein E, Song J, et al. Stinging nettle cream for osteoarthritis. Alternative Therapies. 2009;15(4):60-61.
- Bakhshaee M, Mohammad AH, Esmaeili M, et al. Efficacy of supportive therapy of allergic rhinitis by stinging nettle (Urtica dioica) root extract: A randomized, double-blind, placebo-controlled, clinical trial. Iranian Journal of Pharmaceutical Research. 2017;15:112-118.
- Changping M, Wang M, Aiyireti M, Cui Y. The efficacy and safety of Urtica dioica in treating benign prostatic hyperplasia: A systematic review and meta-analysis. African Journal of Traditional and Complementary Alternative Medicine. 2016;13(2):143-150.
- Codling EE, Rutto KL. Stinging nettle (Urtica dioica) growth and mineral uptake from lead-arsenate contaminated orchard soils. Journal of Plant Nutrition. 2014;37:393-405.
- Basic report: 35205, Stinging nettles, blanched (Northern Plains Indians). National Nutrient Database for Standard Reference Legacy. USDA website. April 2018. Available at: https://ndb.nal.usda.gov/ndb/foods/show/306720. Accessed July 5, 2018.
- Bauman H, Applegate C. Food as medicine: shallot (Allium cepa var. aggregatum, Amaryllidaceae). HerbalEGram. 2017;14(2). Available at: http://cms.herbalgram.org/heg/volume14/02February/FAMShallot.html. Accessed July 5, 2018.
- Farr J. Stinging nettle spanakopita. YMC website. August 10, 2015. Available at: www.yummymummyclub.ca/blogs/jen-farr-hands-on-kitchen/20150729/stinging-nettle-spanakopita-recipe. Accessed July 5, 2018.