Stinging Nettle: Benefits, Dosage, Contraindications

Anticancer

There is interest in using nettle for prostate diseases, especially benign prostatic hyperplasia (BPH) and prostate cancer. Preliminary research shows that a water extract of nettle leaves may decrease the activity of adenosine deaminase (or adenosine aminohydrolase, a hydrolase that catalyzes the reaction in tissues) of the prostate in men with localized prostate cancer. Animal and cell culture research shows that nettle root extract can reduce the proliferation of prostate cancer cells. In vitro research shows that lignans from nettle root interfere with the binding of dihydrotestosterone (DHT) to sex hormone binding globulin (SHBG). The binding of DHT and SHBG stimulates prostate cancer growth. By interfering with this binding, stinging nettle is thought to reduce the growth of prostate cancer. Preliminary research shows that nettle root extract inhibits the sodium-potassium pump in human hyperplastic prostate tissue. Inhibition of the sodium-potassium pump may reduce metabolism and growth of prostate cells.

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Antiandrogenic

SHBG (Sex Hormone Binding Globulin) proteins transport androgens and estrogens at the plasma level. Thus, in men, these hormones bound to SHBG are generally transported to receptor sites on the prostate. With age, testosterone production decreases and the estrogen/testosterone ratio thus increases. This phenomenon then leads to increased synthesis of SHBG transport proteins, which can then prompt prostate tissue cells to divide and grow rapidly, resulting in benign prostatic hyperplasia. Therefore, studies have shown that lignans (including secoisolariciresinols), derived from nettle root extract, inhibit androgen binding to SHBG and also prevent these transport proteins from binding to prostate membrane receptors, thereby limiting proliferative activity on prostate tissues. Other hypotheses have been formulated, indicating an action of nettle root extract on testosterone 5-α-reductase, on other enzymes such as human leukocyte elastase (HLE), a marker of prostatic inflammation by lipophilic steroids of nettle root. Finally, aromatase is responsible for converting testosterone to 17-β-estradiol. This enzyme plays an important role in the pathophysiology of prostate hypertrophy as it specifically induces increased synthesis of androgen receptors and a change in prostate structure. Octadecanoic acids contained in these roots are highly inhibitory of aromatase, according to laboratory experiments.

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Immunomodulatory

Polysaccharides would interact in vitro with T-lymphocytes (immunomodulating activity). Lectins also have immunomodulating activity by stimulating the production of interferon-γ by lymphocytes and by inhibiting autoimmune disorders often found in chronic nonspecific prostatitis.

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Anti-inflammatory

The aerial parts of the nettle and the root have anti-inflammatory effects. Laboratory studies on nettle extract have shown anti-inflammatory activity, notably by inhibiting NF-kappaB activation and reactions derived from cyclooxygenase and 5-lipoxygenase. Phenolic acid isolated from the nettle also reduces leukotriene B4 synthesis. In humans, a study revealed that oral intake of 1.34 g of nettle leaf extract for three weeks significantly decreased TNF-alpha and IL-1-beta levels stimulated by lipopolysaccharides. Additionally, nettle leaf extract reduces the induction of primary T-cell responses and TNF-alpha, suggesting potential in treating diseases like rheumatoid arthritis and Crohn's disease.

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Hypoglycemic

Certain cell cultures and animal research show that nettle leaf can increase insulin secretion from the pancreas. Other cell culture research shows that nettle leaf extract can inhibit the activity of peroxisome proliferator-activated receptors (PPAR)-gamma. Further cell culture research shows that nettle's aerial parts can inhibit alpha-glucosidase activity.

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Hypotensive

Animal research shows that extracts from the aerial parts of stinging nettle can induce an acute hypotensive effect along with diuretic and natriuretic effects (promoting sodium urinary excretion). Leaf juice can increase urinary output and slightly decrease systolic blood pressure and body weight in people with venous insufficiency.

Antiallergic

Nettle leaf, rich in quercetin, could help alleviate allergic rhinitis. Quercetin is recognized for its anti-inflammatory properties and its ability to stabilize mast cells, thereby reducing histamine release. A clinical study showed that daily nettle intake for a month decreased interferon-gamma levels, an inflammation indicator. However, nettle did not significantly improve clinical symptoms of allergic rhinitis, nor did it alter some biological markers associated with this condition.

Diuretic

The leaf and the entire aerial part are slightly diuretic and increase the excretion of chlorides and urea, which is favorable for rheumatism and gout.

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Remineralizing

The leaves contain flavonoids, sterols (sitosterol), numerous organic acids, chlorophyll and carotenoids, vitamins (C, B group, K), and mineral salts (silica, potassium, nitrates, calcium, magnesium). As such, leaves are considered alkalinizing.

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