Avaliação do consumo dietético de potássio e proteína e sua relação com função renal, homeostase de potássio, balanço ácido-base e massa e função muscular em pacientes com doença renal crônica não dependentes de diálise

Abstract

The nutritional recommendations for potassium content and its dietary sources are not stablished for patients with non-dialysis-dependent chronic kidney disease (CKD-NDD). Dietary potassium intake is generally not associated with serum potassium levels, and the relationship between intake with CKD progression and mortality is controversial. To date, no study has evaluated the relationship between potassium intake and its dietary sources with potassium homeostasis, acid-base balance and muscle mass and function which are factors related to the risk of a worse outcome of CKD. The aim of the present study was to evaluate dietary intake of potassium and protein, their main dietary sources, and the relationship with renal function, potassium homeostasis and acid-base status, muscle mass and function in patients with CKD-NDD. This a cross-sectional study conducted in patients with CKD-NDD under regular outpatient treatment in a single center. Data collection and evaluations included: (a) analysis of routine blood parameters and urea, creatinine and potassium in 24-hour urine; (b) analysis of titratable acidity (AT) and ammonium (NH4+) in a single urine sample, and total urinary acid excretion obtained by the sum of AT and NH4+; (c) food intake was assessed by food record (RA) and net endogenous acid production (NEAP) was estimated from dietary protein and potassium values obtained by RA; (d) unifrequency tetrapolar bioimpedance vectors (Biodinamics -310®, Seattle, WA) were used to estimate muscle mass in appropriate equation. Muscle mass, strength, and physical performance were assessed following the standardized methodology. Statistical analyzes included: T-test and ANOVA, or Mann-Whitney and Kruskal-Wallis, Pearson or Spearman correlation, according to normality, and regression for associations. Sixty patients (52% women and 48% men) with CKD-NDD were evaluated, with mean age=62.9±14.6 years, and eGFR=34.9±12.7 mL/min., 55% (n=33) were in stages 3A/3B and 45% (n=27) in stage 4 CKD. Participants were metabolically stable without obvious signs of malnutrition. The dietary intake and the urinary acid excretion were similar between stages 3A/3B and 4. Dietary protein intake was above recommendations, the majority from animal foods, and potassium intake was approximately 2000 mg/day, the majority from vegetable sources. Hyperkalemia and acidosis were observed in around 20% of patients, the majority in stage 4 CKD, and protein and potassium intake, and NEAP were similar among patients without and with acidosis and hyperkalemia. Protein and potassium intake from animal foods were correlated with higher NEAP and higher total urinary acids excretion, the higher acids excretion was associated with a lower risk for low muscle mass and strength. In the present study, potassium and protein dietary intake was not related to the level of renal function in stages 3-4 of CKD, nor with serum levels of potassium and bicarbonate. The high protein and potassium intake from animal foods was associated with high endogenous acid production and also with high renal compensatory effort increasing urinary acid excretion. The low risk of low muscle mass and strength was associated with higher urinary acid excretion.