Health benefits take the sting out of nettles


DOES IT WORK?:Nettles are a good source of vitamins, writes DÓNAL O’MATHÚNA

IF YOU RUB UP against nettles these days, you’re likely to curse their very existence. The stinging pain and welts they cause have led to their Latin name ( Urtica) being used for any similar skin irritation: urticaria.

Yet down through history, many have been thankful for the various ways in which nettles could be used. In ancient times, nettles were woven into fabric.

More recently, nettles have been used to make soups and eaten as a vegetable. They are as nutritious as spinach and other greens, being rich in vitamin C, vitamin K, carotene, potassium and calcium.

In the 19th century, a nettle tonic was believed to promote hair growth. The most likely reason for this was a belief that whatever caused the growth of the tiny hairs on nettle leaves would do likewise for human scalps.

Fresh leaves have been used on arthritic joints as a counter irritant. The idea here is that arthritic pain might be relieved by causing another irritation close to the joint. The leaves also are believed to contain anti-inflammatory agents.

While stories abound of people reporting success with such approaches, little research has been conducted in the area.

Extracts of nettle leaves and roots have had numerous medicinal uses. Probably the oldest application is as a diuretic, where nettle juice was used to increase urinary output, especially for those with symptoms of heart failure or high blood pressure.

Nettles also have been used in various parts of the world to treat asthma, allergies, coughs, kidney problems, rheumatism and prostate difficulties.

Some modern pharmaceuticals have been criticised as drugs looking for a disease to treat. They may be widely used, but their effectiveness for any one condition is questionable.

In a similar way, nettles have been used for many different conditions, but questions remain about their effectiveness in treating any particular condition. Few of the specific uses have been tested in well-controlled trials.

However, two applications have received more study than most, and point to different potential uses of the leaves and the roots.

Extracts of nettle leaves contain a number of compounds that are chemically related to caffeine. Several small studies have found diuretic effects after people used such extracts.

However, most of these studies were uncontrolled and poorly designed. The results were encouraging, although they did not demonstrate a large beneficial effect.

Extracts of nettle roots have received significantly more research, although for a different use.

Benign prostatic hyperplasia (BPH) is a condition in men which causes difficulties with urination along with frequent urges to urinate, especially at night.

Pharmaceutical drugs are available, but have adverse effects. Saw palmetto is a herb used to treat BPH, and nettle root extract has also been recommended. Several uncontrolled studies of nettle root for BPH have been conducted, along with six randomised controlled trials.

Overall, the results have indicated some beneficial effects, although the improvements were relatively small in scale. One study of a combined nettle root and saw palmetto product showed a somewhat larger effect.

Although nettles are highly irritating when encountered in the wild, they have few side effects when taken medicinally or when cooked and eaten. Some people can be allergic to nettles, and others get gastrointestinal irritation after taking the remedies.

Nettles are a highly nutritious food and a good source of vitamins and nutrients. Although they have a long and varied history as medicinal agents, few specific benefits have been clearly demonstrated.

Another difficulty in evaluating nettle remedies arises from the many different ways in which extracts have been made.

The most promising areas deserving further research are nettle leaves as diuretics and nettle root extracts for BPH. Although neither application is strongly supported by current evidence, the results so far have been encouraging.

  • Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He is author of Alternative Medicine: The Christian Handbook, Updated and Expanded Edition, Zondervan, 2007