Role of diet in the management of vasopressin-responsive and -resistant diabetes insipidus.

Dietary protein and NaCl are the precursors of about 60% of the urinary osmoles (urea and NaCl). This investigation tested the hypothesis that in patients with dieabetes insipidus, intake of dietary protein and salt will directly influence the degree of polyuria. Four subjects with pituitary and one with nephrogenic diabetes insipidus were studied. All medications were discontinued. To provide diets ranging between "low-solute" and "high-solute," protein was varied in increments from 40 to 130 g/day and NaCl was varied simultaneously from 0.5 to 10 g/day. In all patients, each increment in protein and salt caused a prompt increase in 24-hr urinary osmoles in the form of urea, Na+, and Cl-. The 24-hr urine volume likewise increased progressively. Average increase in urine osmoles and volume from low- to high-solute diet was +224% and +127%, respectively. In four of the five patients, Reduction of protein/salt intake from habitual dietary at home to the recommedded daily allowance caused a 50 to 100% reduction in the magnitude of polyuria.