Fruit and vegetables are known to have high levels of salicylates, which are also the active anti-inflammatory ingredient of aspirin. Vegetarians meanwhile are known to have low rates of cancer, as well as having higher levels of salicylates in their bodies.

The conventionally grown fruit and vegetables treated with pesticides that are found on many supermarket shelves have lower levels of salicylates than those grown organically.

A review of the possible link between cancer prevention and this substance found in aspirin says many herbs and spices are also especially rich in salicylates. This could explain international differences in cancer rates, the study said.

The salicylates in fruit and vegetables may in fact play a bigger role in protecting against cancer than the antioxidants on which research has focused until now, the researchers say.

Professor Peter Elwood, who led the review, said, "I think this is a very exciting area that should be researched in considerable depth.

"Most medical authorities have said for 20 years that it is the antioxidants in fruit and vegetables that account for their protective effects. It leads us to wonder if the beneficial effects are because of the salicylates they contain," he said.

Salicylates have been found to occur naturally in a wide range of plants. Their role in reducing the likelihood of colon cancer has been previously studied, although uptake by the human body from various sources, and the likely dose needed to impact on health, is difficult to measure.

From the April 13, 2009, Prepared Foods E-dition