Evidence is quietly building to support claims that the plant devil's claw - the name refers to the shrub's hooked, claw-like seedpods - can relieve chronic back pain and osteoarthritis explains Anne Woodham.

Most of the research into the efficacy of devil's claw so far has been carried out in Europe and, while promising, more trials are needed. In a German study involving 75 people with arthritis of the hip or knee, published in Pthertotherapy research in 2003, taking Devil?s claw produced significant improvements in joint pain, stiffness and physical function. In a French study of 122 patients with osteoarthritis of the hip or knee in Phytomedicine in 2000, devil's claw root was as effective in relieving pain and safer than diacerhein, a drug used for osteoarthritis symptoms. A University of Heidelberg trial of 183 patients with lower back pain in 1999 suggested that devil's claw (botanical name Harpagophytum procumbens) could probably benefit many of those who found paracetamol and non-steroidal anti-inflammatories (NSAIDs) helpful, and with fewer side effects (NSAIDs can irritate the gut and cause bleeding and ulceration).

What it does
Herbalists use devil's claw root as an anti-inflammatory, analgesic and digestive stimulant. There are reports that it is more effective in some cases of arthritis than others. Research suggests that its action is due to a number of chemicals called iridoid glycosides, such as harpagoside, that can reduce inflammation in the joints.

The shrub is native to southern Africa, particularly the Kalahari sands of Namibia, where decoctions made from the fleshy tubers growing on its taproot are traditionally used to treat digestive disorders and arthritis.

Recommended dosage
Herbalists suggest adding 300ml of boiling water to one teaspoon of the chopped dried root, steeping for eight hours and straining. This tea is drunk three times a day for at least a month.

Several companies make capsules or tablets containing standardised extracts of the active component, harpagoside, which should be taken according to instructions on the packet. According to the German Pharmacopoeia, a minimum of 1 per cent harpagoside is required, although MedicHerb Devil's Claw contains 2.5 per cent harpagoside. Their recommended dose is one tablet twice daily. Forty tablets of MedicHerb Devil's Claw cost #9.99, available from chemists and health food stores.

Possible side effects
Devil's claw stimulates stomach acid production, though not as much as NSAIDs, so should be avoided if you have stomach or duodenal ulcers. No harmful effects are known, but avoid during pregnancy or breastfeeding or for children under 16 until more studies are done.

Interactions with other treatments/drugs
No drug interactions have been reported.