05 Feb

Can olive leaves help to beat cancer?

By Sarah Vine,

Claims that olive-leaf extract is a ‘miracle’ fighter of disease have caused a great commotion in Athens, reports Peta Bee.

Its fruit is held in reverence and for centuries the tree has been regarded as a gift to the city of Athens from the goddess Athena. But in modern Greece, a health craze for olive leaves is causing rising hysteria that has already resulted in one death.

Suggestions on a television chat show that consuming extract of olive leaves — a bitter, dark-green fluid — can lower cholesterol and fight cancer have led to a frenzied effort by Athenians to get hold of the leaves. Last week the Greek health ministry was forced to call for calm, and a row between two brothers over whether to give a third brother with cancer the supposed miracle cure ended with one stabbing the other to death.

It seems that the furore stemmed from discussions on Greek television about results of a small-scale study into the effects of the gloopy green drink (made by boiling and blending the leaves) on mice with cancer that was conducted at the University of Athens. The Government has given warning that there have been “no tests on the toxicity levels of olive extract and it is possible that it contains hazards”, and an eminent cardiologist, the former health minister Dimi-tris Kremastinos, is urging people not to listen to the “charlatans” talking up the benefits of the plant because “chewing the leaves does nobody any good”. Yet the olive-leaf market is booming, with patients prepared to pay up to £40 a kilo in health shops or stripping the leaves from the olive trees that line the streets of Athens.

Proponents of the olive-leaf theory argue that the claims amount to far more than a passing fad. Olive leaves have long been hailed by naturopaths as a tonic for ailments including the common cold, arthritis, eczema and asthma.

In the early 1900sresearchers discovered a bitter phytochemical compound called oleuropein in the leaves of certain olive trees which proved to be partly responsible for the trees’ powerful resistance to diseases. Since then the active compounds have been shown in small trials to possess antiviral, antibacterial and antifungal properties effective in the treatment of many conditions for which antibiotics and other conventional medications have been found to be ineffective. Thirty years ago Italian researchers showed that oleuropein could be used to lower blood pressure in animals, and it has since been used widely by practitioners of herbal medicine to treat cardiovascular problems.

“Their use is certainly not new,” says Dr Anne Walker, a herbalist and researcher in human nutrition at the University of Reading school of food biosciences. “Olive-leaf tinctures, made by steeping the leaves in alcohol at room temperature, are often used by registered herbalists as a treatment for cardiovascular problems including lowering of blood pressure and cholesterol. There is also some evidence that they have an antidiabetic effect in susceptible people.”

Although they are by no means conclusive, the cancer claims are not, it seems, without foundation either. Last July the results of a trial carried out at the Australian Centre for Complementary Medicine Education and Research (ACCMER), a joint venture between Southern Cross University in New South Wales and the University of Queensland, were published. They suggested that olive-leaf extract in supplement form (as capsules or granules) could ward off some forms of the disease.

Dr Lesley Stevenson, the principal researcher from the Southern Cross natural products pharmacology unit, says that early laboratory tests seemed to indicate that the antioxidant-rich oil from the leaves “can destroy human breast and prostate cancer cells”. The researchers plan to carry out further investigations to find out exactly how lethal olive leaves are to cancer cells.

While the high levels of monounsaturated fats in olive oil (made from the crushed or pressed fruit) mean that it is good for the heart, the leaves of the plant have been shown to provide ten times more disease-fighting antioxidants. Studies by ACCMER in 2005 found that olive leaves have five times the antioxidant capacity of vitamin C and almost double that of green tea or grapeseed extract. According to Dr Stevenson, her team also discovered that extract of olive leaf was more powerful at getting rid of damaging free radicals than such acclaimed antioxidants as grapeseed extract and vitamin E — and that furthermore it could help to fight some inflammatory conditions.

Cancer charities do not dismiss these findings but are understandably treating the olive-leaf research with some caution. “Studies into any potential anticancer properties of olive-leaf extract are at an extremely early stage,” says Sue Green, a nurse with the charity Cancerbackup. “Many more years of research are needed to see if this will ever become an actual treatment for people with cancer.”

Dr Julie Sharp, of Cancer Research UK, says that “while a few small laboratory studies have suggested that extracts from olive leaves might have anticancer properties, there is still not enough evidence to confirm these observations”.

But that evidence could become more convincing as the results of new studies emerge. Clinical trials at the New York University school of medicine found the natural extract to be effective against HIV without being toxic to uninfected cells, and further investigations are planned.

Meanwhile, those seeking the health tonic who don’t wish to make their own tea from the pale-green leaves — see below — can opt to take olive-leaf extract as a supplement or a liquid (both are available from health stores or online). Manufacturers such as Olive Leaf Australia recommend taking a teaspoonful of the liquid three times a day with food, adding that it can also be applied topically to help to heal wounds.

Cosmetics manufacturers are also beginning to add olive-leaf extract to their products on the premise that it has antibacterial properties and helps to soothe the skin. The Johnson’s Baby Natural range contains it, as does Simply Organic hair and scalp wash.

Others remain steadfastly sceptical about the leaves’ beneficial effects. “The anticancer claims appear to be based on the fact that the leaves are high in antioxidants — and the best way to boost your intake of these compounds is through ordinary fruit and vegetables,” says Bridget Aisbitt, a nutrition scientist with the British Nutrition Foundation. “If your diet is sufficiently varied you don’t need to resort to nutritional fads, which are sometimes as harmful as they are helpful.”

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