High glycaemic-index (GI) foods, including processed and fast foods, are an unsuspected cause of lung cancer, while eating plenty of fruits and vegetables can prevent the disease, say researchers.

The risk was discovered when researchers compared the eating habits of 1,905 people, who had recently been diagnosed with lung cancer, with 2,413 healthy people. There was an average 49 per cent higher risk between those eating high- or low-GI foods.

But the risk doubled among people who had never smoked, say researchers from the University of Texas MD Anderson Cancer Centre.

Their discoveries explain why a growing minority of non-smokers are developing lung cancer, they say.

High-GI foods include sugary drinks and foods, white bread and white rice, chips, biscuits and cakes, and most commercial breakfast cereals. The foods cause a sudden spike in blood-sugar levels, which raise insulin levels.