Cooking with vegetable oils releases toxic chemicals linked to cancer and other diseases, according to leading scientists, who are now recommending food be fried in olive oil, coconut oil, butter or even lard.

The results of a series of experiments threaten to turn on its head official advice that oils rich in polyunsaturated fats - such as corn oil and sunflower oil - are better for the health than the saturated fats in animal products.

Vegetable oil could be one of the most unhealthy cooking oils.

Scientists found that heating up vegetable oils led to the release of high concentrations of chemicals called aldehydes, which have been linked to illnesses including cancer, heart disease and dementia.

Martin Grootveld, a professor of bioanalytical chemistry and chemical pathology, said that his research showed "a typical meal of fish and chips", fried in vegetable oil, contained as much as 100 to 200 times more toxic aldehydes than the safe daily limit set by the World Health Organisation.