Saw Palmetto & Nettle Clinical Evidence

Planta Medica
Mittman P. Randomized, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis. 1990 Feb;56(1):44-7. 

Topic: 
Can freeze-dried stinging nettles (Urtica dioica) help relieve symptoms in subjects with allergic rhinitis?

Background:
Stinging nettles grow in Asia, North Africa, Europe, and North America and have been used in folk medicine as early as the 10th century to treat rheumatism and arthritis. Since both of these diseases are characterized by an inflammatory response, might nettles treat allergy symptoms as well?

Study Type:
Human clinical intervention trial

Study Design:
Double-blind, randomized. Subjects kept a daily symptom diary and were assessed by the researchers after 1 week of treatment. Subjects took the stinging nettles when allergy symptoms appeared and rated their symptoms as dramatically improved, moderately improved, unchanged or worse 1 hour later.

Subjects:
98 subjects (69 completed) with allergic rhinitis

Dosage:
300 mg, at onset of symptoms, for 1 week

Results:
While diaries showed the nettle treatment to be only slightly more effective than placebo, global assessments indicated that nettles was significantly more effective than placebo. In fact, the treatment was found to be moderately or highly effective in 58% of the treatment group as compared to just 37% of the placebo group.

Journal of Herbal Pharmacotherapy 
Safarinejad MR. Urtica dioica for treatment of benign prostatic hyperplasia: a prospective, randomized, double-blind, placebo-controlled, crossover study. 2005;5(4):1-11. 

Topic: 
Does nettles aid in the alleviation of urinary symptoms of benign prostatic hyperplasia?

Background:
Nettles has been used as a diuretic and to relieve joint pain for many years in traditional medicine.

Study Type:
Human clinical intervention trial

Study Design::
Double-blind, placebo-controlled, randomized, partial crossover, comparative trial: Patients were randomly assigned to take either nettles or placebo for 6 months.

Subjects:
558 men with lower urinary tract symptoms due to benign prostatic hyperplasia

Dosage:
Not specified

Results:
At the end of the 6-month trial: 

  • 81% of men receiving nettles supplements reported improved lower urinary tract symptoms compared to 16% of men receiving placebo
  • IPSS went down from 19.8 to 11.8 with nettles, compared to 19.2 to 17.7 with placebo
  • Peak urinary flow rates improved by 8.2 mL for treated patients, versus 3.4 mL for placebo recipients
  • Post-void residual urine volume dropped in the nettles group from an initial value of 73 mL to 36 mL; however there was no appreciable change seen in the placebo group

Conclusion:
In the present study, Urtica dioica have [sic] beneficial effects in the treatment of symptomatic BPH.

MMW Fortschritte der Medizin 
Popa G, Hägele-Kaddour H, Walther C. Efficacy of a combined Sabal-urtica preparation in the symptomatic treatment of benign prostatic hyperplasia. Results of a placebo-controlled double-blind study. 2005 Oct 6;147 Suppl 3:103-8. 

Topic: 
Does the combination of saw palmetto and nettles improve symptoms of benign prostatic hyperplasia (BPH)?

Background:
Saw palmetto and nettles have both been shown individually to improve urinary symptoms caused by enlarged prostate. Researchers studied whether the combination of the two herbs is also efficacious.

Study Type:
Human clinical intervention trial

Study Design::
Double-blind, placebo-controlled trial: Half of the subjects were assigned to take supplements of saw palmetto + nettles for 24 weeks, while the other half received placebo.

Subjects:

Men with benign prostatic hyperplasia
Dosage:
160 mg saw palmetto + 120 mg nettles, twice daily for 24 weeks

Results:
Over the study period, saw palmetto + nettles significantly improved nighttime urination frequency and urgency compared to placebo. The treated group also experienced improved quality of life compared to the placebo group.

Conclusion:
The often distressing symptoms of BPH can be effectively ameliorated already after only a few weeks of treatment with the sabal-urtica preparation.

International Urology & Nephrology 
Lopatkin N, et al. 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. 2007;39(4):1137-46. 

Topic: 
Does the combination of saw palmetto and nettles improve symptoms of benign prostatic hyperplasia (BPH) in a long-term study?

Background:
This study, which lasted considerably longer than the first study, was the second to investigate whether the combination of saw palmetto and nettles is efficacious in treating BPH.

Study Type:
Human clinical intervention trial

Study Design::
Open label extension of a randomized, double-blind, placebo-controlled trial: Patients were first treated with either saw palmetto + nettles or placebo for 24 weeks, followed by a 24-week control period and a 48-week follow-up period in which all subjects received the active treatment.

Subjects:
257 elderly men with moderate or severe lower urinary tract symptoms caused by BPH for the first arm; 219 for the second follow-up arm

Dosage:
160 mg saw palmetto + 120 mg nettles twice daily

Results:

At the end of 96 weeks:

  • The International Prostate Symptom Score fell by 53%
  • Peak and average urinary flow increased by 19%
  • Residual urine volume decreased by 44%

Conclusion:
Treatment with saw palmetto + nettles provides a clinically relevant benefit over a period of 96 weeks.

 

 

 

Saw Palmetto Mechanism of Action:

Saw palmetto extract has the power to reduce prostate growth by inhibiting the action of 5-alpha reductase, an enzyme that converts testosterone to the more harmful dihydrotestosterone (DHT). BPH patients treated with saw palmetto extract experience reduced levels of DHT, especially in the periurethral region (near the urethra). Enlargement of this area can cause urinary blockage.Saw palmetto also inhibits the action of epidermal growth factor (EGF) to cause growth and inflammation of prostate epidermal cells (thoselining the prostate). 

 

Nettle Mechanism of Action:

Stinging nettle may also reduce production of histamine by inhibiting the action of histamine receptors and by preventing cells from releasing pro-inflammatory mediators. Nettle extract also inhibits the production of pro-inflammatory prostaglandins by reducing levels of COX-1 and COX-2, enzymes that cause pain and inflammation. 

It also works in multiple ways to prevent and heal ulcers: 

  • It inhibits the action of pepsin, a digestive enzyme that can cause gastric bleeding.
  • It prevents a decrease in the content of gastric mucus, which protects the stomach from irritation.
  • It increases the expression of basic fibroblast growth factor, vascular endothelial growth factor, and ornithine decarboxylase — all of which help heal the gastric mucosa.
  • It down-regulates the expression of tumor necrosis factor, a cytokine that causes inflammation in ulcerated tissue.
  • It’s an antioxidant that can alleviate damage to the gastric mucosa and promote the healing of ulcers.
  • It protects cells in the stomach lining by increasing levels of heme oxygenase and heat shock protein (HSP72), which helps protect cells from stress.
  • It increases gastric microcirculation.
  • It reduces the secretion of acid.
  • It may promote cell proliferation and differentiation during ulcer healing, allowing the lesions to close.
  •  

 

Nettle Root Mechanism of Action:

Nettle root extract is thought to work by modulating the levels of several substances. These include sex hormone binding globulin (SHBG, a protein that binds to testosterone), aromatase (an enzyme responsible for the synthesis of estrogen), EGF (epidermal growth factor), and prostate steroid membrane receptors. It also has anti-inflammatory activity.