Dietary sodium chloride intake independently predicts the degree of hyperchloremic metabolic acidosis in healthy humans consuming a net acid-producing diet

We previously demonstrated that typical American net acid- producing diets predict a low- grade metabolic acidosis of severity proportional to the diet net acid load as indexed by the steady- state renal net acid excretion rate ( NAE). We now investigate whether a sodium ( Na) chloride ( Cl) containing diet likewise associates with a low- grade metabolic acidosis of severity proportional to the sodium chloride content of the diet as indexed by the steady- state Na and Cl excretion rates. In the steady- state preintervention periods of our previously reported studies comprising 77 healthy subjects, we averaged in each subject three to six values of blood hydrogen ion concentration ([ H]b), plasma bicarbonate concentration ([ HCO3-]p), the partial pressure of carbon dioxide ( P-CO2), the urinary excretion rates of Na, Cl, NAE, and renal function as measured by creatinine clearance ( CrCl), and performed multivariate analyses. Dietary Cl strongly correlated positively with dietary Na ( P < 0.001) and was an independent negative predictor of [ HCO3-]p after adjustment for diet net acid load, P-CO2 and CrCl, and positive and negative predictors, respectively, of [ H] b and [ HCO3-]p after adjustment for diet acid load and P-CO2. These data provide the first evidence that, in healthy humans, the diet loads of NaCl and net acid independently predict systemic acid- base status, with increasing degrees of low- grade hyperchloremic metabolic acidosis as the loads increase. Assuming a causal relationship, over their respective ranges of variation, NaCl has similar to 50 - 100% of the acidosisproducing effect of the diet net acid load.