American Journal of Clinical Nutrition, Vol 56, 169-173, Copyright © 1992 by The American Society for Clinical Nutrition, Inc

ORIGINAL RESEARCH COMMUNICATIONS

Influence of dietary protein on glomerular filtration and urinary albumin excretion in insulin-dependent diabetes

WJ Kalk, C Osler, J Constable, M Kruger and V Panz
Division of Endocrinology and Metabolism, University of the Witwatersrand Medical School, Johannesburg, South Africa.

We investigated the effects of dietary constituents on glomerular filtration (GFR) and albumin excretion rates (AERs) in a cross- sectional study in 39 young subjects with insulin-dependent diabetes. Dietary protein intake correlated significantly in patients with GFRs less than 150 mL/min per 1.73 m2 (r = 0.53, n = 23, P = 0.009), but not with AER. GFR also correlated with mean blood glucose at a concentration less than 12.0 mmol/L (r = 0.61, P = 0.0035). Protein and fat intakes were similar in patients with and without microalbuminuria (AER greater than 20 mg/L) but long-term glycemic control was worse in the former [HbA1 12.4 +/- 2.9% (mean +/- SD) and 10.6 +/- 2.1%, respectively, P = 0.043]. In seven patients, short-term reduction of dietary protein from 2.0 to 1.0 to 0.5 g.kg-1.d-1 produced a progressive fall in GFR by 11.6 +/- 6.0 and 9.6 +/- 5.9 mL/min, respectively (P less than 0.05), but did not consistently affect AER. We conclude that both dietary protein and glycemic control influence GFR but neither alone appears to explain glomerular hyperfiltration. Microalbuminuria was associated with poor glycemic control but not with dietary fat or protein consumption.