Healthy people rightly consider food for its culinary rather than its biochemical value. With the present state of knowledge, only broad guidelines are appropriate as to what constitutes a healthy diet. In some conditions, however, diet can be critically important to health. This imposes a considerable strain on patients and their families, and maintaining a stringent dietary regimen for a long time is notoriously difficult.

Suggestions from animal studies that restricting dietary protein might slow or abort a steady fall in the glomerular filtration rate aroused much interest in those managing potentially progressive renal disease.1,2 After these early reports several small but disciplined studies of the value of restricting protein intake in humans were published, and these were subjected to a meta-analysis reported in this journal.3 The authors concluded that the evidence strongly supported the effectiveness of low protein diets in delaying the onset of end stage renal disease, and the need for a large prospective trial was recognised. Such a trial has now been published4; it found little evidence that rigorous protein restriction slows the progression of renal disease in humans.

The modification of diet in renal diseases study reported that no significant benefit followed dietary intakes of …