Nettles: there is more to it than the sting.

Stinging nettle (Urtica dioica) is one plant you learn about quickly when you walk into it. The serrated leaves and stems are covered with stinging hairs that contain histamine, serotonin, and acetylcholine. When the stinging hairs are touched, they can cause local irritation and a burning sensation that may last for several hours. Fortunately, the stinging hairs on the plant are inactivated by drying or cooking the plant.

Stinging nettle, also called nettles, is a perennial herb native to Europe and the United States. It can also grow in most other temperate regions of the world. The commercial product originates from Germany, the Balkans, and regions of the former Soviet Union. The plant grows from two to five feet tall. Both the aerial parts and the root may be harvested and used for medicinal purposes. It is important that the leaves, greenish-white flowers, and stems of nettles be collected during the flowering season.

Many Uses

The stinging nettle plant has been used historically as a mild diuretic; to treat infections of the lower urinary tract, anemia, hemorrhoids, asthma, hay fever, and other allergies; to stop bleeding; and to heal wounds. American Indians use nettles to treat rheumatic conditions, such as arthritis. Nettle tea has also been used for eczema and other chronic skin conditions. Some people enjoy cooking the young leaves and eating them as a green vegetable. They do contain a variety of vitamins and minerals. Today, a nettle extract is used to formulate skin and hair care products.

Preparations of the aerial parts (leaf, flower, and stem) of stinging nettles are considered safe when used appropriately. No interactions with food or with other drugs are known. Potentially nettles could adversely react with sedatives or anticoagulants. Taking during pregnancy is not recommended because of possible stimulatory effects on the uterus.

Diuretic and Anti-Inflammatory Activity

Stinging nettle preparations have produced a positive diuretic effect in clinical trials. High levels of flavonoids in nettles may contribute to its diuretic action. Patients with cardiac or chronic venous insufficiency who were treated with stinging nettle juice for two weeks experienced a significant increase in urinary output and a slight decrease in systolic blood pressure. The hypotensive effect of nettles has also been seen in experimental animals. Nettle leaves have been recommended for inflammatory diseases of the lower urinary tract.

Traditionally nettles are used for symptomatic treatment of joint pains. In Germany nettle extracts are used to help treat rheumatic complaints with some measure of success. The pain and stiffness experienced by patients with acute arthritis have been partially relieved by consuming stewed stinging nettle. When consumed along with the anti-inflammatory drug Diclofenac, stinging nettle was observed to enhance the anti-inflammatory activity of low doses of the drug. The phenolic acids and polysaccharides in nettles are thought to provide its anti-inflammatory activity.

A tea can be prepared by taking the finely cut aerial parts of nettles and steeping them in boiling water for 10 minutes. This preparation can be consumed three to four times a day.

Relief for the Prostate

Stinging nettle root preparations are commonly used for the symptomatic relief of urinary difficulties associated with benign prostatic hyperplasia (BPH). The nettle preparations are typically used for painful and frequent urination, excessive nighttime urination, and urine retention in BPH patients.

In a clinical trial lasting 11 months that involved patients with stage I or stage 2 BPH, improvement of urinary flow in men treated with a combination nettle root-saw palmetto (Serenoa repens) fruit extract was similar to that observed in those receiving the drug Finasteride. Symptoms associated with an enlarged prostate were almost identical for both treatment groups. Adverse reactions, however, were fewer for the nettles-saw palmetto treatment group than for the Finasteride group.

In another study physicians assessed the nettle root-saw palmetto extract treatment as safe and effective and well tolerated, and patients reported an improvement in their prostatic symptoms. In a Polish study in which a stinging nettle-pygeum (Prunus africanum) bark preparation was used for eight weeks, patients experienced an improvement in urinary flow and a decrease in residual urine and frequency of nighttime urination.

Furthermore, when stinging nettle extract alone was given to elderly BPH patients, a significant improvement in urinary flow and volume resulted after nine weeks, compared with the placebo group. Stinging nettle root generally relieves the symptoms of an enlarged prostate without reducing the enlargement. The active substances responsible for the action of stinging nettle root are unknown, but the root does contain some polysaccharides, plant sterols, and terpenoids that could explain its activity.

Root preparations of nettles are safe to use. No interactions are known to occur with food or drugs. Occasionally mild gastrointestinal complaints may result. The root can be taken either as a tea or in the form of capsules or tablets.

Remember:

Herbal products and dietary supplements can have pharmacological effects, may produce adverse reactions in some people, and could interact with over-the-counter and prescription medications you may take. Discuss with your physician your decision to use any herbal product. Anything mentioned in this article is not intended to diagnose, prescribe, or treat any ailment.

Winston J. Craig, Ph.D., R.D., is a professor of nutrition at Andrews University, Berrien Springs, Michigan.