A total of 12 patients with absorptive
hypercalciuria type II and 11 normal controls participated in a study to evaluate the effects of
dietary protein levels on urinary
calcium and
oxalate excretion before and after a 1 gm. dose of
oxalate. Two test periods were used during which
calcium (less than 400 mg. per day) and
oxalate were restricted. The first test was done under conditions of low
dietary protein (12 per cent total caloric intake, 60 gm.) and the second test was done at a high
protein level (25 per cent, 125 gm.
protein). Twelve-hour urine specimens were obtained after dinner on day 3 of each diet (low and high
protein) and again on day 4 when 1 gm.
oxalate (spinach) was added to the dinner meal. The specimens were analyzed for
calcium, oxalate and relative
calcium oxalate saturation (concentration product ratio). There were no significant differences between the controls and subjects with absorptive
hypercalciuria type II in
oxalate excretion before the
oxalate load on the low
protein (controls 31.4 +/- 4.2 standard error, expressed as mmol.
oxalate per mol.
creatinine, and absorptive
hypercalciuria type II 23.1 +/- 3.1) and high
protein (controls 30.4 +/- 4.2 and absorptive
hypercalciuria type II 28.8 +/- 5.9) diets. After the
oxalate bolus the positive changes in
oxalate excretion were 11.8 +/- 4.8 (low
protein) and 17.8 +/- 4.7 (high
protein) for controls, and 11.4 +/- 4.4 (low
protein) and 31.8 +/- 5.2 (high
protein) for patients with absorptive
hypercalciuria type II. Thus, the increases in post-load urinary
oxalate levels observed for controls and patients were greater on the high
protein than on the
low protein diets. After the
oxalate load the increases in urinary
oxalate and
calcium oxalate supersaturation were significantly greater for patients with absorptive
hypercalciuria type II than for control subjects for the high
protein but not the
low protein diets (p less than 0.05).