Different parts of the nettle herb have been used for different indications. Most evidence comes from traditional usage as nettle has not been significantly investigated under controlled conditions as a stand-alone treatment.
Traditionally, nettle herb and leaf have been used to treat painful joint diseases, and scientific investigation now shows there is a demonstrable benefit with its use.
One randomised, double-blind crossover study involving 27 patients with OA pain at the base of the thumb or index finger compared topical applications of stinging nettle leaf with placebo, used daily for 1 week. After a 5-week washout period, treatments were then reversed. Nettle application used for 1 week showed reduction in pain and disability and produced significantly superior results to placebo. An open study of 17 patients reporting beneficial effects with the nettle sting of U. dioica showed that a transient urticarial rash can be associated with topical use. It is suspected that a counterirritant effect is chiefly responsible.
In a multicentre study of 152 subjects with degenerative rheumatic conditions, 1.54 g dried nettle herb extract produced a subjective improvement in 70% of cases after 3 weeks.
Four other studies using a nettle-leaf extract reported that most subjects rated the treatment as good or very good (ESCOP 2003).
Commission E approved as supportive therapy for rheumatic ailments when used internally or applied externally.
BENIGN PROSTATIC HYPERPLASIA
In practice, nettle root preparations are often prescribed in combination with other herbal medicines, such as saw palmetto or pygeum. Representative of clinical practice, most studies have investigated the effects of nettle in combination with other herbs and have generally yielded positive results.
Open studies involving a total of over 1 5 000 men with BPH have found significant improvements in prostate size, night-time urination, frequency of urination, urine flow and residual urine. One double-blind study over 9 weeks of nettle extract in 50 men with BPH showed a significant decrease in sex hormone binding globulin and non-significant improvements in micturition volume and maximum urinary flow; however, the authors explain that the results were due to inappropriate length and dosage of therapy. In another double-blind, placebo-controlled study, treatment of 67 men with nettle produced a 14% improvement in urine flow and a 53% decrease in residual urine. An open study of 30 patients with BPH showed that nettle root extract over an average of 3.5 months significantly decreased residual urine volume and increased maximal urinary flow in 50% of cases. Marked subjective relief was also reported.
Urtica and Pygeum
In one study, 134 patients with BPH were randomly assigned an Urtica and Pygeum preparation (300 mg U. dioica root extract combined with 25 mg P. africanum bark extract) or a preparation containing half that dose under double-blind test conditions for 8 weeks. Both treatments significantly increased urine flow, and reduced residual urine and nocturia after 28 days, whereas after 56 days, further significant decreases were found in residual urine (half-dose group) and in nocturia (both groups).
Nettle and saw palmetto extract
In 1995, an open, prospective, multicentre observational study involving 419 specialist urological practices investigated the efficacy and tolerability of a saw palmetto and nettle combination in 2080 patients with BPH. Herbal treatment was seen to improve pathological findings and obstructive and irritative symptoms. Both efficacy and tolerability were assessed by physicians as very good or good and most patients reported an improvement in general QOL and reduction in symptoms of BPH.
A randomised, multicenter, double-blind study involving 543 patients with early stage BPH found that a combination of nettle and saw palmetto extract was as effective as finasteride at increasing maximum urinary flow and improving International Prostate Symptom Scores (IPSS) after 24 weeks’ treatment, which continued to improve by week 48. Improvement in QOL scores were similarly observed with both treatments, regardless of prostate size. Overall, the two treatments only differed in regard to adverse reaction incidence, with the herbal combination much better tolerated. A 2003 review concluded that a combination of nettle and saw palmetto is safe and effective for the treatment of lower urinary tract symptoms associated with benign prostatic hyperplasia, comparable to the alpha-blocker tamsulosin.
A randomised, placebo controlled, double-blind, multicentre trial in 2005 further demonstrated the effectiveness of saw palmetto fruit (160 mg) and nettle root (120 mg) for lower urinary tract symptoms due to prostate enlargement: 257 men aged 50 years or more were randomised to take either two capsules of the study medication (320 mg saw palmetto and 240 mg nettle root) daily or placebo for 24 weeks. Men on the treatment experienced a 35% reduction in symptoms, most notably intermittency, hesitancy, urgency and nocturia, compared to 24% for placebo. At the end of the 24-week period an open trial was conducted for an additional 24 weeks and all men were given the herbal medicine. Those previously taking placebo reported significant improvements when switched to the study medication.
Commission E approved the use of Urtica root for difficulty in urination in BPH stages 1 and 2.
A double-blind randomised study showed that a freeze-dried preparation of nettles improved global assessments of allergic rhinitis after 1 week’s therapy.
Stinging Nettle: Dosage Range
• Dry extract: 0.6-2.1 g/day in divided doses; or
• Liquid extract (1:2): 2-6 mL/day.
• Although Commission E recommend 4-6 g/day cut root for symptoms of BPH, doses up to 18 g/day have been used.