Serum lipid changes associated with modified protein diets: results from the feasibility phase of the Modification of Diet in Renal Disease Study.

The use of low-protein diets for the management of progressive renal insufficiency may require increases in dietary fats to maintain caloric balance. This raises the concern that such diets might exacerbate the lipid problems already prevalent in chronic renal insufficiency. We present a study in which protein-restricted diets were followed by a group of patients with renal insufficiency without a compensatory increase in fat calories and without adverse effects on serum lipids. Ninety-six patients with renal insufficiency were enrolled in the feasibility phase of the Modification of Diet in Renal Disease Study and were assigned to dietary protein intakes of 1.3, 0.575, or 0.28 g/kg body weight/d. The last diet was supplemented with amino acids or their keto analogs. Of this group, 25 participants were excluded from the present study of lipids because of changes in their intake of medications with known effects on serum lipids, three were excluded because of proteinuria increasing by more than 2 g/d, and seven were excluded because of incomplete measurements. For the remaining 61 participants, median serum total cholesterol at baseline was 215 mg/dL. In 72% of participants it exceeded the age- and sex-adjusted median of the Lipid Research Clinics Prevalence Study. Glomerular filtration rates varied from 8 to 56 mL/min/1.73 m2. The patients' serum lipid levels were stable by 6 months on assigned diets. Serum total and low-density lipoprotein cholesterol levels tended to decrease with reduced protein intake. The baseline to follow-up change in protein intake calculated from urinary urea measurements was significantly correlated with the change in serum total cholesterol (Spearman r = 0.31, P < 0.05) and also with change in low-density lipoprotein cholesterol (r = 0.34, P < 0.01). Surprisingly, correlations between change in serum cholesterol and intake of fats were small in magnitude and did not approach statistical significance. Protein intake did correlate, however, with intake of cholesterol. We conclude that the use of low-protein diets for patients with renal insufficiency did not adversely affect serum lipids.