Stinging nettle: benefits, dosage, contraindications

Anticancer

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

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Antiandrogenic

SHBG (Sex Hormone Binding Globulin) transport proteins carry androgens and estrogens in the plasma. Thus, in men, those hormones bound to SHBG are generally transported to receptor sites on the prostate. With age, testosterone production decreases and the estrogen/testosterone ratio then increases. This phenomenon leads to an increased synthesis of SHBG transport proteins which can stimulate prostate tissue cells to divide and grow rapidly, resulting in benign prostatic hyperplasia. Studies have shown that lignans (including secoisolariciresinols) derived from nettle root extract inhibit the binding of androgens 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 proposed indicating an action of nettle root extract on testosterone 5-alpha-reductase, on other enzymes such as HLE (human leukocyte elastase), a marker of prostatic inflammation by lipophilic steroids from the root. Finally, aromatase is responsible for the conversion of testosterone to 17-beta-estradiol. This enzyme plays an important role in the pathophysiology of prostate hypertrophy since it notably induces increased synthesis of androgen receptors and a change in prostate structure. The octadecanoic fatty acids contained in these roots are strong inhibitors of aromatase, according to laboratory experiments.

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Immunomodulator

Polysaccharides may interact in vitro with T lymphocytes (immunomodulatory activity). Lectins also have immunomodulatory activity by stimulating the production of interferon-γ by lymphocytes, and by inhibiting autoimmune disorders frequently found in non-specific chronic prostatitis.

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Anti-inflammatory

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

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Hypoglycemic

Some cell culture and animal studies show that nettle leaf may increase insulin secretion from the pancreas. Other cell culture research shows that nettle leaf extract may inhibit the activity of peroxisome proliferator-activated receptor gamma (PPAR-gamma). Other cell culture studies show that the aerial parts of nettle may inhibit alpha-glucosidase activity.

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Antihypertensive

Animal studies show that extract from the aerial parts of stinging nettle can induce an acute hypotensive action, as well as diuretic and natriuretic effects (promoting urinary sodium excretion).nnLeaf juice can increase urine output and slightly reduce systolic blood pressure and body weight in people with venous insufficiency.nn

Anti-allergic

The nettle leaf, rich in quercetin, may help relieve allergic rhinitis. Quercetin is known 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 one month lowered interferon-gamma levels, an indicator of inflammation. However, nettle did not significantly improve the clinical symptoms of allergic rhinitis nor alter certain biological markers associated with this condition.nn

Diuretic

The leaf, like all the aerial parts, is mildly diuretic and increases the excretion of chlorides and urea, which is beneficial for rheumatism and gout. nn

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Remineralizing

The leaves contain flavonoids, sterols (sitosterol), numerous organic acids, chlorophyll and carotenoids, vitamins (C, B complex, K) and minerals (silica, potassium, nitrates, calcium, magnesium). As a result, the leaves are considered alkalizing.nn

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