NETTLES FOR TEA

by Ann Wild

The stinging nettle, Urtica dioica L., has been used as a healing herb at least since the time of Dioscorides in the first century AD. It was recommended by Saint Hildegard of Bingen in the twelfth century for the treatment of lung disorders and forgetfulness. In the seventeenth century, Culpepper also recommended the nettle to "open the passages of the lungs" and for a wide variety of other complaints. In fact, stinging nettle has been recommended by herbalists over the centuries to treat at least sixty different disorders. Nettles have been said to be tonic, diuretic, to regulate the digestion and purify the blood, to cure a cough, to stop bleeding and to heal wounds and boils. They have been used to treat cancer, hepatitis, bile duct disorders, constipation, bronchial asthma and other lung diseases, anaemia, diabetes, dropsy, dysentery, menstrual problems, gastritis, neuralgia, rheumatism, gout, piles and even dandruff.

Can one herb really treat sixty different disorders? Modern pharmacologists have not been able to identify any active ingredients which could account for the effects claimed for the nettle. The information passed down to us from the herbalists of previous centuries seems to vary considerably in reliability. How are we to distinguish genuine observations from the products of fashionable theories such as the Signatura plantarum which claimed that the appearance of a plant reflects the diseases it will cure or the astrological belief that plants and diseases are associated with certain planets?

Modern medicine has two methods of clarifying the efficacy of herbal drugs. It can test the drug in clinical trials and it can analyze the herbs chemically. Although stinging nettle preparations have been tested in a number of clinical trials, most authorities do not consider the results to be reliable. One study demonstrated the diuretic action of the pure pressed plant juice, but the methods used in this trial have been widely criticized. Several trials have reported beneficial effects of an extract from stinging nettle roots on urinary symptoms which accompany the early stages of prostate gland enlargement, but improvements in objective parameters such as retained urine volume were not found. The stinging nettle extract, however, did cause a reduction in the levels of a protein (SHBG) which binds the sexual hormone, androgen, an objective finding whose significance is still unclear. A freeze-dried preparation of stinging nettle was tested recently for the treatment of allergic rhinitis but the improvements reported were not very convincing.

Chemical analyses of the stinging nettle have identified largely compounds found in all green leafy plants: chlorophyll, carotinoids, vitamins and minerals. Nettles contain high levels of potassium which reinforce the water diuresis produced by the herbal tea. As the replacement of potassium during the use of diuretics is important, nettle tea can truly be recommended in the supporting treatment of complaints such as bladder infections where the patient is advised to drink large quantities of fluid. Stinging nettles contain the vitamins typical of green leafy vegetables: vitamin C, B2, pantothenic acid, vitamin K1, and ß-carotene which is converted into vitamin A in the liver. The young leaves are recommended as a spring vegetable, prepared like spinach. Nettles were one of the earliest spring greens available to our ancestors and so it is understandable that Culpepper claims that the nettle "consumes the phlegmatic superfluities in the body of man, that the coldness and moisture of winter has left behind". Stinging nettle root has been shown to contain ß-sitosterol, a steroid known to reduce raised levels of blood cholesterol and to have beneficial effects on prostatic urinary symptoms. However, ß-sitosterol is found in many vegetables: a balanced diet supplies up to 300 milligrams every day. A daily dose of 4 grams stinging nettle root contains only 10 to 50 milligrams total ß-sitosterol, not enough, it is thought, to account for the effects on urinary symptoms which have been described. The analyses have not explained the specific effects claimed for the stinging nettle but they have demonstrated beyond doubt that tea prepared from stinging nettle leaves or whole herb (Urtica foliae or Urtica herbae) can only be good for you.

© Ann E. Wild

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