Origin: Europe, Israel
Part of the plant used: Leaves of young plants
Stinging nettles grow throughout the world. Their name is derived from the presence of stinging hairs on their leaves and stems which when touched inject formic acid and histamine into the skin and cause urticaria, (or irritation and inflammation). Nettles have been widely used as food, medicine, cosmetics, and clothing.
Pharmacology - Nettles are a rich source of trace elements, absorbing and accumulating them. Nettles contain formic acid and the neurotransmitters acetylcholine, 5-hydroxy tryptamine, and histamine which are responsible for the sting. These constituents are thought to endow nettles with their antiarthritic and antirheumatic and expectorant properties.
Medicinal Uses - Because of their rich nutritional content, nettles have traditionally been given to anemic, exhausted, debilitated or recuperating people as soups or teas. The stinging properties are lost when the plant is cooked. Nettles also have been traditionally used as an important hair and skin tonic. The high quantity of silicon has made nettles highly useful in stimulating hair growth, improving the condition of the hair and skin and treating dandruff. Nettles have been used internally and externally to treat eczema. Nettle juice has been used as an astringent or styptic to stop bleeding and to treat wounds. The best known use of nettles is in the treatment of gout and other rheumatic conditions. A decoction of the leaves or the expressed juice has been shown to mobilize uric acid from the joints and eliminate it through the kidneys. Recently a randomized, double-blind, clinical trial has shown the usefulness of nettles in the treatment of allergic rhinitis or hayfever.
Nettle Root Extract - About 90% of testosterone is produced by the testes, the remainder by the adrenal glands. Testosterone functions as an aphrodisiac hormone in brains cells, and as an anabolic hormone in the development of bone and skeletal muscle. But testosterone that becomes bound to serum globulin is not available to cell receptor sites and fails to induce a libido effect. It is, therefore, desirable to increase levels of "free testosterone" in order to ignite sexual arousal in the brain. A hormone that controls levels of free testosterone is called sex hormone-binding globulin (SHBG). When testosterone binds to SHBG, it loses its biological activity and becomes known as "bound testosterone," as opposed to the desirable "free testosterone." As men age past year 45, SHBG's binding capacity increases almost dramatically-by 40% on average-and coincides with the age-associated loss of libido.
Some studies show that the decline in sexual interest with advancing age is not always due to the amount of testosterone produced, but rather to the increased binding of testosterone to globulin by SHBG. This explains why some older men who are on testosterone replacement therapy do not report a long-term aphrodisiac effect. That is, the artificially administered testosterone becomes bound by SHBG, and is not bioavailable to cellular receptor sites where it would normally produce a libido-enhancing effect. It should be noted that the liver also causes testosterone to bind to globulin. This liver-induced binding of testosterone is worsened by the use of sedatives, anti-hypertensives, tranquilizers and alcoholic beverages. The overuse of drugs and alcohol could explain why some men do not experience a libido-enhancing effect when consuming drugs and plant-based aphrodisiacs. An interesting review, "How Desire Dies" (Nature, 381/6584, 1996), discusses how frequently prescribed drugs, such as beta-blockers and antidepressants, cause sexual dysfunction. Prescription drugs of all sorts have been linked to inhibition of libido.
Logically, one way of increasing libido in older men would be to block the testosterone-binding effects of SHBG. This would leave more testosterone in its free, sexually activating form. A highly concentrated extract from the nettle root provides a unique mechanism for increasing levels of free testosterone. Recent European research has identified constituents of nettle root that bind to SHBG in place of testosterone, thus reducing SHBG's binding of free testosterone. As the authors of one study state, these constituents of nettle root "may influence the blood level of free, i.e. active, steroid hormones by displacing them from the SHBG bindings site."
The prostate gland also benefits from nettle root. In Germany, nettle root has been used as a treatment for benign prostatic hyperplasia (enlargement of the prostate gland) for decades. A metabolite of testosterone called dihydrotestosterone (DHT) stimulates prostate growth, leading to enlargement. Nettle root inhibits the binding of DHT to attachment sites on the prostate membrane. Nettle extracts also inhibit enzymes such as 5 alpha reductase that cause testosterone to convert to DHT. It is the DHT metabolite of testosterone that is known to cause benign prostate enlargement, excess facial hair and hair loss at the top of the head.
Contra-indications - Large doses of nettles may cause an upset stomach, burning skin, or urinary complications. If harvesting nettles, be sure to wear long gloves, long sleeved shirts and pants to avoid stings. Nettle may interfere with anti-inflammatory, antihypertensive, sedative, or blood sugar-lowering medications. However, no problems have yet been reported.
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