Medicine is and always has been full of unproven concepts. However, when they are frequently used in clinical practice, they seem established and are therefore seldom questioned. In his book ‘Follies and fallacies in medicine’ (Glasgow, The Tarragon Press, 1989) Peter Skrabanek clearly proposed a way to improve the quality of medicine by being chronically sceptical towards all ‘established’ concepts. By cyting Bertold Brecht he proposed ‘scepticemia’ as a major tool to speed up the progress in medicine: ‘The chief cause of poverty in science is imaginary wealth. The chief aim of science is not to open a door to infinite wisdom but to set a limit to infinite error.’ In this article we will try to analyze the evidence of the three so-called cornerstones of diabetes therapy – diet, exercise and insulin – with regard to their efficacy in reaching the goals of treatment in type 1 (insulin-dependent) diabetes.