Benefits in nutritional interventions in patients with CKD stage 3-4

The efficacy and safety of protein-restricted diets in chronic kidney disease (CKD) is still a matter of debate. However, several studies have clearly demonstrated the beneficial effects of such diets on the outcome of patients with stage 3-4 CKD. This point has been confirmed by 4 recent studies. In 2009, a meta-analysis showed that protein restriction significantly delayed the time to renal death with a substantial economic benefit for the health service. Although toxicity of urea has since long been considered as negligible, an experimental model in rats has shown a direct role of urea in the development of oxidative stress and insulin resistance, which are among the leading mechanisms of cardiovascular complications in CKD. These latter results confirm an interest in studying reduction in blood urea levels as observed in patients kept on a low-protein diet (LPD) or on a supplemented very-low protein diet (SVLPD). A reduction in proteinuria, which is associated to a LPD, has the following prognostic value: the more important the reduction in proteinuria, slower is the decline in renal function. This effect, which is additive to the one of an angiotensin-converting enzyme inhibitor (ACEI), is higher with SVLPD than with conventional LPD. Safety of a reduced protein intake has been confirmed by the study on the long-term outcomes (11 years) of patients already on SVLPD. The difference between these results and those from the extended follow-up of the modification of diet in renal disease (MDRD) study, in which no recommendations were made after the completion of the trial, confirms the importance of a close nutritional survey of patients with CKD who are put on a protein-restricted diet.