Study Question: Which diet is most effective for slowing the progression of diabetic nephropathy?

Setting: Outpatient (specialty)

Study Design: Randomized controlled trial (nonblinded)

Synopsis: Animal models of diabetic nephropathy suggest that a diet with high intake of polyphenol and low availability of iron with carbohydrate restriction may prolong kidney function. In this trial, 191 consecutive patients referred to nephrology clinics who had type 2 diabetes and established nephropathy were randomized (allocation concealment uncertain) to a conventional protein-restricted diet or a 50-percent carbohydrate-restricted, low-iron-available, polyphenol-enriched diet (CR-LIPE) diet. No information was provided on whether outcomes were assessed blindly.

Investigators followed 89 percent of the patients for an average of 3.9 years. Using intention-to-treat analysis, renal replacement therapy or death occurred less often in patients on the CR-LIPE diet than on the conventional diet (20 percent versus 39 percent;P <.01; number needed to treat = five). This difference was independent of blood pressure, average A_1c level, initial level of renal dysfunction, and use of angiotensin-converting enzyme inhibitors.

Bottom Line: A 50-percent CR-LIPE diet is superior to a conventional protein-restricted diet for prolonging survival and avoiding renal replacement therapy in patients with type 2 diabetes and established renal disease. Patients should be referred to a dietitian for guidance on how to maintain this diet. (Level of Evidence: 1b)