Sodium chloride supplementation and urinary calcium excretion in postmenopausal women

It was hypothesized that variations within the range of usual salt intakes of North Americans influence urinary excretion of calcium in healthy postmenopausal women. The effects of sodium chloride supplements of 0.51, and 102 mmol/d, randomly assigned to 17 healthy, noninstitutionalized, postmenopausal women consuming their usual diets were compared. Diets and discretionary salt intake were repeated exactly for three experimental periods of 4 d each for 3 consecutive weeks. Supplementing with 51 mmol NaCl/d increased average daily urinary excretion of Ca, Na, and Cl by 0.5, 51.0, and 48.9 mmol respectively, urine pH by 0.1, and serum Cl by 1.5 mmol/L (p less than 0.05). Supplementing with 102 mmol/d induced additional increases in these variables (p less than 0.05). Assuming a total body mass of 900 g Ca and no decrease in renal or fecal losses, additions of 51 and 102 mmol/d NaCl to the diet for 10 y would mobilize Ca stores of 7.5% and 10%, respectively, and could thus constitute a risk factor for osteoporosis.