Steaming, boiling or stewing foods such as meat and cheese is healthier than grilling or frying it, say scientists researching a new class of toxic compounds found in the human diet, which have been implicated in diabetes, heart complaints and Alzheimer's disease.

The compounds, known collectively as "advanced glycation end products" or AGEs, result from a chemical reaction between sugars and animal proteins or fats, typically during frying or pasteurisation. The research, carried out at the Mount Sinai School of Medicine in New York, showed high AGE levels in the bloodstream of young, healthy individuals and even higher levels in older people.