When most people think of nettles they think of stinging nettles and the rashes that can develop from contact with the leaves. However, the genus Urtica encompasses a large number of plant species that grow across North America and Europe. Nettles are perennial shrubs that can grow to around one and half meters in height with yellow and white flowers, and growing and harvesting of certain varieties of nettle plant results in a number of medicinally useful preparations. In particular, the leaves and the roots (rhizomes) of Urtica dioica L. and Urtica urens L, are used in tonics and teas. The use of nettle as a medicine dates back centuries in herbalism, and as well as a large body of anecdotal evidence, scientific studies support a role for nettle as a medicinal herb. The exact medicinal properties of the nettle plants depends on the parts of the plant used. Evidence support a role for nettle root in the treatment of benign prostate hyperplasia, and a role for the leaves in the treatment of gout, arthritis and hay fever.
The differing medicinal properties of the leaves and roots is a product of their differing nutritional components. Generally the leaves are more commonly available in teas and decoctions. The leaves contain a number of amines including histamine, choline, acetylcholine and serotonin, maining in the stinging hairs. These components contribute to the rash that develops when on contact with the stinging hairs. Nettle leaves also contain a number of acids including formic acid, malic acid, carbonic acid and silicic acid, which are also found in the stinging parts of the leaves. In addition, the leaves also contain a range of polyphenols including a number of members of the flavonol subgroup of flavonoids which includes quercetin, kaempferol, isoquercetin and rutin and a range of large molecular weight tannins. A number of terpenes are also found in high concentrations in nettle leaves. As with all green leafy plants the nettle leaves are a rich source of chlorophyll (around 5 mg per gram of leaf weight).
The leaves can also contain high levels of minerals such as calcium, iron, potassium and silicon, although the exact mineral content of the leaves will depend on the soil and growing conditions. Studies have also detected a range of vitamins in nettles including vitamin A, vitamin C, vitamin D, vitamin E and vitamin K, in addition to a range of B vitamins. The differing medicinal properties of the nettle roots reflects their very different nutritional profile. Scientific investigation has identified a small molecular weight lectin in nettle called Urtica dioica agglutinin, which is a monomeric protein with a particularly high concentration of glycine, cysteine and tryptophan. The roots of nettle, as the leaves, also contain a number of sterols (plant steroids) that include 3-beta sitosterol and sitosterol 3-D-glucoside. However, the roots generally contain much higher concentrations of sterols than the leaves. The roots and leaves also contain a number of lignans, which fall under the broad category of dietary fibre.
Studies have investigated the effects of nettle root extract on biomarkers thought to be relevant to the development of benign prostate hyperplasia (BPH). In particular, nettle root may be effective because constituents of the plant act as a weak aromatase inhibitor that may prevent the conversion of testosterone to the more androgenic dihydrotestosterone, high levels of the latter being linked to hyperplasia of the prostate. One of the current medicinal treatments for BPH is the aromatase inhibitor drug finasteride. In one study, an extract of nettle combined with a herbal extract of saw palmetto were equally effective as the drug finasteride at treating BPH. The medicinal properties of nettle leaf against arthritis and hay fever likely relates to its high antioxidant content that may confer anti-inflammatory effects. Nettle leaves possess diuretic properties which may be useful in treating gout. It is thought the diuresis increases the urinary excretion of uric acid, thus reducing the deposition of uric acid in joints.
Dr Robert Barrington’s Nutritional Recommendation: Nettle tea is widely available and scientific evidence suggests that it has medicinal properties over a range of conditions, particularly those that have an aetiology involving oxidative stress. In addition, the diuretic effects of nettle leaves may have certain specific applications. Nettle root is generally not as widely available as nettle leaf, but it is commercially available through a number of suppliers. Nettle in combination with saw palmetto may be a useful treatment in cases of BPH, and of course could be taken as a weak aromatase inhibitor to reduce the risk of developing the condition. The lack of side effects and the generally high levels of essential and nonessential nutrients suggests that nettle leaf and nettle root can be incorporated into a healthy diet either as a treatment for specific conditions or as a general tonic for preventive effects.