Research Questions Low-Calcium Treatment for Kidney Stones

PARMA, Italy--A diet low in salt and meat with normal calcium intake may be more effective than a diet low in calcium for treating symptoms related to idiopathic hypercalciuria (abnormally high amounts of calcium in the urine), according to Italian researchers at the University of Parma (NEJM, 346:77-84, 2002) (www.nejm.org). One symptom that is of particular concern to patients suffering from hypercalciuria is calcium oxalate stones (kidney and/or bladder stones).

A five-year randomized trial compared two diets in 120 men with recurrent calcium oxalate stones and hypercalciuria. Half of the men were assigned to a diet containing a normal amount of calcium (30 mmol/d) but reduced amounts of animal protein (52 g/d) and salt (50 mmol/d of sodium chloride). The other 60 men were assigned to a traditional low-calcium diet, which contained 10 mmol/d of calcium and no restrictions on salt or protein intake.

At the end of five years, 20 percent of the 60 men on the normal-calcium, low-animal-protein, low-salt diet and 38 percent of the 60 men on the low-calcium diet had relapses. Both groups demonstrated drops in urinary calcium levels at follow up; however, urinary oxalate excretion increased in the men on the low-calcium diet but decreased in those on the normal-calcium, low-animal-protein, low-salt diet. Researchers concluded that in men with recurrent calcium oxalate stones and hypercalciuria, restricted intake of the animal protein and salt, combined with normal calcium intake, may provide greater protection than the traditionally recommended low-calcium diet.