Relationship between nutritional status and the glomerular filtration rate: Results from the MDRD Study

Background. The relationship between the protein-energy nutritional status and renal function was assessed in 1785 clinically stable patients with mod erate to advanced chronic renal failure who were evaluated during the basel ine phase of the Modification of Diet in Renal Disease Study. Their mean +/ - SD glomerular filtration rate (GFR) was 39.8 +/- 21.1 mL/min/ 1.73 m(2). Methods. The GFR was determined by I-121-iothalamate clearance and was corr elated with dietary and nutritional parameters estimated from diet records. biochemistry measurements, and anthropometry. Results. The following parameters correlated directly with the GFR in both men and women: dietary protein intake estimated from the urea nitrogen appe arance, dietary protein and energy intake estimated from dietary diaries, s erum albumin, transferrin. percentage body fat, skinfold thickness, and uri ne creatinine excretion. Serum total cholesterol, actual and relative body weights, body mass index, and arm muscle area also correlated with the GFR in men. The relationships generally persisted after statistically controlli ng for reported efforts to restrict diets. Compared with patients with GFR > 37 mL/min/ 1.73 m(2), the means of several nutritional parameters were si gnificantly lower for GFR between 21 and 37 mL/min/1.73 m(2), and lower sti ll for GFRs under 21 mL/min/1.73 m(2). In multivariable regression analyses , the association of GFR with several of the anthropometric and biochemical nutritional parameters was either attenuated or eliminated completely afte r controlling for protein and energy intakes. which were themselves strongl y associated with many of the nutritional parameters. On the other hand, fe w patients showed evidence for actual protein-energy malnutrition. Conclusions. These cross-sectional findings suggest that in patients with c hronic renal disease, dietary protein and energy intakes and serum and anth ropometric measures of protein-energy nutritional status progressively decl ine as the GFR decreases. The reduced protein and energy intakes, as GFR fa lls, may contribute to the decline in many of the nutritional measures.