Supplements & Herbs

Stinging nettle medicinal effects

Urtica dioica and Urtica urens

Scientific research studies show wide-ranging therapeutic potential (Part 2)

The best things in life are free, and the humble but "powerful" stinging nettle perfectly fits that description. The following compilation is a continuation of Part 1 which (in addition to an introductory explanation why the stinging nettle deserves a place of honour, both for its nutritional and therapeutic value) covers validated scientific research into stinging nettles'

mineral, trace element and toxicant content
phytochemical diversity
safety
antioxidant and antimicrobial effects
immune-enhancing effects
antitumor and cancer-related activity and
effect on diabetes and its various complications.

Regarding the use of animals in some of the research listed in the following, the same remarks apply as already stated. Also please note that there are several dozen additional studies into the nettles' medicinal effects involving animals not listed here.

Urtica (stinging nettles): cardiovascular effects

Cardiovascular effects of Urtica dioica L. in isolated rat heart and aorta.
www.ncbi.nlm.nih.gov/PubMed/12237804

(Phytotherapy Research, 2002)
Cardiovascular effects of Urtica dioica L. (Urticaceae) roots extracts: in vitro and in vivo pharmacological studies.
www.ncbi.nlm.nih.gov/PubMed/12020933

Published in the Journal of Ethnopharmacology in 2002, this study aimed to evaluate a possible cardiovascular action of the nettle root. Applying crude aqueous and methanolic extracts to aortic preparations with an intact and functional pre-contracted endothelial layer was found to trigger vasodilation.
Inhibition of rat platelet aggregation by Urtica dioica leaves extracts.
www.ncbi.nlm.nih.gov/PubMed/16619332

This study (published in Phytotherapy Research in 2006) concluded that Urtica dioica has antiplatelet activity which supports its traditional use in treating or preventing cardiovascular disease.

Urtica (stinging nettles): effects on prostate, male health, SHBG, bioavailable testosterone

Urtica dioica for treatment of benign prostatic hyperplasia.
www.ncbi.nlm.nih.gov/PubMed/16635963

This prospective, randomized, double-blind, placebo-controlled, crossover study was printed in the Journal of Herbal Pharmacotherapy (2005). It found Urtica dioica treatment to have beneficial effects on symptomatic benign prostatic hyperplasia (BPH) without causing side effects.
Evaluation of 5a-reductase inhibitory activity of certain herbs useful as antiandrogens
www.ncbi.nlm.nih.gov/PubMed/23710567

This study published in Andrologia (2014) found that among eleven plants investigated, Urtica dioica was one of five promising candidates for further exploration into their antiandrogenic activity (i.e. ability to counteract the effects of male sex hormones).
Analysis of the results obtained with a new phytotherapeutic association for LUTS (lower urinary tract symptoms) versus control. [corrected].
www.ncbi.nlm.nih.gov/PubMed/20931547

This study published in Urologia (2010) found marked benefits regarding quality of life in the intervention group compared to controls,´and no noteworthy adverse events, making the tested phytotherapeutic combination (which contained a high dose of Urtica dioica) very effective for the treatment of lower urinary tract symptoms in patients with benign prostatic hyperplasia.
Studies on the binding of Urtica dioica agglutinin (UDA) and other lectins in an in vitro epidermal growth factor receptor test.
www.ncbi.nlm.nih.gov/PubMed/23196016

Published in Phytomedicine: International Journal of Phytotherapy and Phytopharmacology in 1995, the German researchers concluded that Urtica dioica agglutinin "may be the major antiprostatic compound of Urtica dioica drug".
Combined sabal and urtica extract compared with finasteride in men with benign prostatic hyperplasia: analysis of prostate volume and therapeutic outcome.
www.ncbi.nlm.nih.gov/PubMed/10971268

Published in BJU International (2000), this analysis showed equivalent efficacy of the herbal treatment (saw palmetto fruit and nettle root extracts) and finasteride. However, more patients in the group treated with finasteride experienced adverse events than in the group treated with saw palmetto and nettle root.
Efficacy and safety of a combination of Sabal and Urtica extract in lower urinary tract symptoms--long-term follow-up of a placebo-controlled, double-blind, multicenter trial.
www.ncbi.nlm.nih.gov/PubMed/18038253

The herbal treatment provided "a clinically relevant benefit over a period of 96 weeks" (published in International Urology and Nephrology, 2007).
Combined extract of Sabal palm and nettle in the treatment of patients with lower urinary tract symptoms in double blind, placebo-controlled trial.
www.ncbi.nlm.nih.gov/PubMed/16708583

This Russian study published in Urologiia (2006) found that the herbal treatment was superior to placebo in attenuating lower urinary tract symptoms. The herb extracts were well tolerated and effective even in patients with severe symptoms.
Combined extracts of Urtica dioica and Pygeum africanum in the treatment of benign prostatic hyperplasia: double-blind comparison of two doses
www.ncbi.nlm.nih.gov/PubMed/7509261

(Clinical Therapeutics, 1993)
The Efficacy of Stinging Nettle (Urtica Dioica) in Patients with Benign Prostatic Hyperplasia: A Randomized Double-Blind Study in 100 Patients
www.ncbi.nlm.nih.gov/pmc/articles/PMC3589769/

Published in the Iranian Red Crescent Medical Journal (2013), this 8-week study showed significant differences (relief of clinical symptoms) after treatment in the nettle group. Again, no side effects were observed.
Stinging nettle root extract (Bazoton-uno) in long term treatment of benign prostatic syndrome (BPS). Results of a randomized, double-blind, placebo controlled multicenter study after 12 months.
www.ncbi.nlm.nih.gov/PubMed/15045190

Published in Der Urologe Ausg. A (2004), this study had 246 patients take Bazoton uno (a dry extract of stinging nettle roots) for a year. Less adverse events and urinary infections occurred under Bazoton uno treatment than under placebo, so the stinging nettle extract was considered a safe therapeutic option for benign prostatic syndrome.
Long-term efficacy and safety of a combination of sabal and urtica extract for lower urinary tract symptoms--a placebo-controlled, double-blind, multicenter trial
www.ncbi.nlm.nih.gov/PubMed/15928959

This prospective trial investigated the efficacy and tolerability of a fixed combination of sabal fruit extract and urtica root extract in a total of 257 patients with benign prostatic hyperplasia.

After 24 weeks of double-blind treatment, patients administered the herbal combination showed a higher total score reduction (according to the International Prostate Symptom Score) both in obstructive and irritative urinary symptoms, than patients treated with placebo. The herbal combination was extremely well tolerated. (published in the World Journal of Urology, 2005)
Efficacy of a combined Sabal-urtica preparation in the symptomatic treatment of benign prostatic hyperplasia. Results of a placebo-controlled double-blind study.
www.ncbi.nlm.nih.gov/PubMed/16261945

Another German study into the combination sabal-urtica treatment arriving at similar results (with positive effects showing within a few weeks of treatment), published in MMW Fortschritte der Medizin, 2005.

For the healthy functioning of their bodies, both sexes produce and require testosterone (although in different amounts). With increasing age, the levels of bioavailable testosterone tend to diminish, however.

This is not due to decreasing production of testosterone (in fact, production appears to remain unchanged throughout life) but to the fact that testosterone becomes increasingly bound to a water-soluble monomeric protein named albumin, as well as to the so-called "sex-hormone-binding-globulin" (SHBG).

For various reasons — including the intake of oral contraceptives — SHBG levels tend to increase over time. Additionally, SHBG can "help" bind estrogen to prostate cell membranes, triggering an increase in PSA.

To restore circulating testosterone to healthy levels (freeing up the currently bound testosterone) and reverse the binding process, nettles are one of several herbs (others are saw palmetto and wild oats) that can be safely used. Some relevant research studies include

Lignans from the roots of Urtica dioica and their metabolites bind to human sex hormone binding globulin (SHBG).
www.ncbi.nlm.nih.gov/PubMed/9434605

This in-vitro study printed in Planta Medica (1997) found that several lignans contained in the roots of the stinging nettle possess a binding affinity to SHBG, and addressed potential benefits of plant lignans on BPH.
The effect of extracts of the roots of the stinging nettle (Urtica dioica) on the interaction of SHBG with its receptor on human prostatic membranes.
www.ncbi.nlm.nih.gov/PubMed/7700987

Printed in Planta Medica in 1995, this study aimed to elucidate the mechanisms underlying the effect of stinging nettle root extracts in BPH treatment. It found that an aqueous Urtica extract inhibited the binding of SHBG in a dose-related manner all the way to complete inhibition.
Plant constituents interfering with human sex hormone-binding globulin. Evaluation of a test method and its application to Urtica dioica root extracts.
www.ncbi.nlm.nih.gov/PubMed/7702715

(Zeitschrift für Naturforschung. C, Journal of Biosciences, 1995)

Urtica (stinging nettles): anti-inflammatory effects (arthritis and rheumatism)

Phytalgic, a food supplement, vs placebo in patients with osteoarthritis of the knee or hip.
www.ncbi.nlm.nih.gov/PubMed/20015358

Published in Arthritis Research & Therapy in 2009, this randomised double-blind placebo-controlled clinical trial run over three months concludes with the observation that the tested food supplement (containing fish oils, urtica dioica, zinc, and vitamin E) apparently lowered the requirement for painkillers and nonsteroidal anti-inflammatory drugs while improving the symptoms of osteoarthritis such as stiffness, with the observed clinical effect appearing considerably larger than that of any other known product.
Is Phytalgic(R) a goldmine for osteoarthritis patients or is there something fishy about this nutraceutical? A summary of findings and risk-of-bias assessment.
www.ncbi.nlm.nih.gov/PubMed/20156334
Plant extracts from stinging nettle (Urtica dioica), an antirheumatic remedy, inhibit the proinflammatory transcription factor NF-kappaB.
www.ncbi.nlm.nih.gov/PubMed/9923611

(Published in FEBS Letters, 1999) This German study looked into the mode of action of standardized extracts of stinging nettle leaves used as antiinflammatory remedies in rheumatoid arthritis. Study results suggested that Urtica's antiinflammatory effect may partially be owed to its inhibitory action on NF-kappaB activation. (free full text available)
Ex-vivo in-vitro inhibition of lipopolysaccharide stimulated tumor necrosis factor-alpha and interleukin-1 beta secretion in human whole blood by extractum urticae dioicae foliorum.
www.ncbi.nlm.nih.gov/PubMed/8740085

Published in Arzneimittelforschung (1996), this study concluded that its findings regarding the pharmacological action of Urtica dioica leaf extract might explain the stinging nettle's beneficial effects on rheumatic diseases.
Anti-inflammatory effect of Urtica dioica folia extract in comparison to caffeic malic acid
www.ncbi.nlm.nih.gov/PubMed/8821518

Published in Arzneimittelforschung (1996), this study concluded that Urtica's antiphlogistic effects shown in vitro might explain the pharmacological and clinical effects of nettle leaf extract upon rheumatoid diseases.
Antinociceptive and anti-inflammatory effects of Urtica dioica leaf extract in animal models.
www.ncbi.nlm.nih.gov/PubMed/25050274

Published in the Avicenna Journal of Phytomedicine (2013), this study corroborates the traditional use of nettle extract in painful and inflammatory conditions. (free full text available)
Lipophilic stinging nettle extracts possess potent anti-inflammatory activity, are not cytotoxic and may be superior to traditional tinctures for treating inflammatory disorders.
www.ncbi.nlm.nih.gov/PubMed/23092723

Published in Phytomedicine in 2013, this study examined extracts of the leaves, stems, roots and flowers of Urtica dioica for cytotoxic and anti-inflammatory activities. Taken together, the study results suggest that using lipophilic extracts of stinging nettle could be more effective for treating inflammatory disorders (particularly arthritis) than traditional tinctures.
Stinging nettle cream for osteoarthritis.
www.ncbi.nlm.nih.gov/PubMed/19623834

(Alternative therapies in health and medicine, 2009)
General practice study with nettle extract. Arthrosis patient need fewer non-steroidal anti-inflammatory drugs.
www.ncbi.nlm.nih.gov/PubMed/12154480

A German-language study published in MMW Fortschritte der Medizin, 2002.

Urtica (stinging nettles): effects on brain and memory (animal studies)

The beneficial effects of nettle supplementation and exercise on brain lesion and memory in rat.
www.ncbi.nlm.nih.gov/PubMed/19071007

This study published in the Journal of Nutritional Biochemistry (2009) inter alia found that nettle supplementation decreased the level of reactive oxygen species and had an antioxidant effect in rats.
The effect of exercise and nettle supplementation on oxidative stress markers in the rat brain.
www.ncbi.nlm.nih.gov/PubMed/15862920
The results of this study published in Brain Research Bulletin (2005) suggested that both exercise and nettle affect the functioning of the brain. Nettle was shown to work as an effective antioxidant, lowering free radical concentration and enhancing brain cell survival.

Urtica (stinging nettles): effects on allergies

Natural treatment of perennial allergic rhinitis.
www.ncbi.nlm.nih.gov/PubMed/11056414

This study published in Alternative Medicine Review (2000) arrived at the conclusion that Urtica dioica as well as other natural substances may be used as a safe primary treatment or in tandem with conventional approaches.
Nettle extract (Urtica dioica) affects key receptors and enzymes associated with allergic rhinitis.
www.ncbi.nlm.nih.gov/PubMed/19140159

This study, published in Phytotherapy Research in 2009, showed that in vitro a nettle extract inhibits several important inflammatory events that underlie seasonal allergies.
Randomized, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis.
www.ncbi.nlm.nih.gov/PubMed/2192379

Published in Planta Medica (1990), this study compared the effects of a freeze-dried nettle preparation against placebo in 69 individuals suffering from allergic rhinitis and found a slight advantage in the treatment group.
Note: Urtica itself has no allergenic significance, see www.ncbi.nlm.nih.gov/PubMed/17042140 .

Urtica (stinging nettles): multiple medicinal effects

Pharmacological and toxicological evaluation of Urtica dioica.
www.ncbi.nlm.nih.gov/PubMed/23036051

Published in Pharmaceutical Biology 2013, this animal study tested the antiinflammatory, antidiabetic, antibacterial and toxicological properties of nettle leaf extract. The findings showed nettle leaves to be an intriguing source of bioactive compounds, "justifying their use in folk medicine to treat various diseases".

Urtica (stinging nettles): nettle sting against pain

Nettle sting of Urtica dioica for joint pain--an exploratory study of this complementary therapy
www.ncbi.nlm.nih.gov/PubMed/10581821

(Complementary Therapies in Medicine, 1999) An interview of eighteen patients using stinging nettle to treat their joint pain, including dosage, mode of application and effects. Seventeen reported that nettles therapy had been very helpful. Apart from a transitory rash, patients observed no side effects.
Randomized controlled trial of nettle sting for treatment of base-of-thumb pain
www.ncbi.nlm.nih.gov/PubMed/10911825

Apparently the first randomized controlled double-blind crossover study on the use of nettle sting for arthritis pain. Printed in the Journal of the Royal Society of Medicine in 2000, this trial was set up to confirm or invalidate the numerous references to this folk remedy published in the past.

For seven days, 27 patients with osteoarthritic pain in their thumb or index finger applied Urtica dioica leaf to the painful area. Compared against the effect of placebo, reductions in both pain and disability were significantly greater in the treatment group, thus confirming the therapeutic validity of yet another "primitive" folk remedy.
Nettle sting for chronic knee pain: a randomised controlled pilot study.
www.ncbi.nlm.nih.gov/PubMed/18514907

(Complementary Therapies in Medicine, 2008)
The use of nettle stings for pain
www.ncbi.nlm.nih.gov/PubMed/17985812

(Alternative Therapies in Health and Medicine, 2007)
Please note that apparently, a similar healing effect can be obtained by applying a nettle tincture (alcoholic extract of stinging nettle leaves) to the area of concern.

Urtica (stinging nettles): effects on Aids / HIV

The mannose-specific plant lectins from Cymbidium hybrid and Epipactis helleborine and the (N-acetylglucosamine)n-specific plant lectin from Urtica dioica are potent and selective inhibitors of human immunodeficiency virus and cytomegalovirus replication in vitro
www.ncbi.nlm.nih.gov/PubMed/1329650

Antiviral Research, 1992
Carbohydrate-binding agents cause deletions of highly conserved glycosylation sites in HIV GP120: a new therapeutic concept to hit the achilles heel of HIV
www.ncbi.nlm.nih.gov/PubMed/16183648

This study published in the Journal of Biological Chemistry in 2005 among other results showed that Urtica dioica's N-acetylglucosamine-binding protein prevented entry of HIV.

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