Using olive oil in cooking may prevent the development of bowel cancer, research shows.

Writing in the medical journal Gut, a team from Barcelona say their findings suggest that olive oil may have some protective qualities.

Their findings may explain why a Mediterranean diet appears to be so healthy.

The researcher was carried out on rats who were fed a diet rich in olive, fish, or safflower oil.

Each group was then divided into two and half of the animals were given a cancer-causing agent.

Four months later the researchers found those rats on the olive oil diet had less pre-cancerous tissue and fewer tumours than those fed the other oils.

Five percent fat diet

Lead researcher Professor Miguel Gassull said: "This study provides evidence that a five percent fat diet containing olive oil as compared with a five percent safflower oil diet prevents colonic carcinogenesis in rats."

The fish oil diet also appeared to have some positive impact on reducing cancerous tissue.

Professor Gassull and his team said the olive oil diet reduced the amount of a chemical called arachidonate, which when combined with a substance called prostaglandin E can promote cancer.

The researchers believe constituents of olive oil such as flavonoids, squalene and polyphenols may help to protect against cancer.

Flavonoids and polyphenols are antioxidants which help prevent cell damage from oxygen-containing chemicals called free radicals.

However, the team says further work needs to be carried out before the exact mechanism by which olive oil might help to ward off cancer can be determined.

Dr Wynnie Chan, of the British Nutrition Foundation, said olive oil had already been shown to protect against heart disease as it was a good source of mono-unsaturated fatty acids.

However, she warned against assuming that an anti-cancer effect in rats would be replicated in mice.

She said: "Olive oil in the diet is absolutely fine, but it should not be used too liberally as we should still be watching fat intake."