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Diet may slow progression of diabetic nephropathy

J Fam Pract. 2003 September;52(9):664-688
By
Anne Mounsey, MD
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  • BACKGROUND: Patients with end-stage renal disease are usually encouraged to follow a low-protein diet to slow the progression of their renal disease. This study was conducted to determine whether a carbohydrate-restricted, low-iron/polyphenol-enriched (CR-LIPE) diet was more effective than a conventional protein-restricted diet at slowing the progression of diabetic nephropathy. Foods rich in polyphenols include olive oil, green tea, cranberries, grapes, and red wine.
  • POPULATION STUDIED: A total of 191 patients with type 2 diabetes— men and women aged 49 to 62 years who were referred to nephrology clinics in California for impending renal failure—were recruited. Subjects had a history of diabetes for 5 to 15 years, with glycosylated hemoglobin (HbA1C) of 6.0% to 9.3%. Current medications for both hypertension management and glucose control were continued. When there was doubt as to the cause of renal failure, a renal biopsy was performed to confirm the diagnosis of diabetic nephropathy. The ethnicity of the subjects is not mentioned. Results are likely generalizable to a diabetic population with advanced renal disease seen in a nephrology clinic.
  • STUDY DESIGN AND VALIDITY: This was a nonblinded, randomized controlled trial, although the method of randomization is not specified. Subjects were assigned with concealed allocation to either the CR-LIPE diet or the control diet, a conventional proteinrestricted diet (0.8 g/kg). The main features of the CR-LIPE diet were 50% carbohydrate reduction; iron-enriched meats are replaced with iron-poor meats and foods known to inhibit iron absorption; elimination of all beverages apart from tea, water, and red wine; and the use of olive oil for frying and dressings. No attempt was made to assess compliance to either diet.
  • OUTCOMES MEASURED: Disease-oriented outcomes included doubling of serum creatinine and end-stage renal disease as defined by serum creatinine >6.0 mg/dL. Patientoriented outcomes included the need for renal replacement therapy or transplantation and allcause mortality.
  • RESULTS: No significant difference was seen in the baseline characteristics of the 2 groups. Serum creatinine doubled in 19 (21%) of patients on the CR-LIPE diet vs 31 (39%) control subjects (P<.01). Renal replacement therapy or death occurred in 18 (20%) of patients on the CR-LIPE diet and in 31 (39%) control subjects (P<.01; number needed to treat=5).
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PRACTICE RECOMMENDATIONS

A polyphenol-enriched diet with 50% carbohydrate restriction and low iron availability was superior to a conventional protein-restricted diet in slowing the progression of diabetic nephropathy.

These findings must be confirmed by additional high-quality studies before physicians can routinely recommend a change from the conventional low-protein diet. Current use of this diet is limited, as many nutritionists— even those specializing in diabetes—have no knowledge of it.

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