Kidney Stones: Water, Calcium and the DASH Diet

When caring for patients after a kidney stone, the best first step is often the simplest: impress upon them that drinking lots of water is their medicine. For the majority of patients, water is more likely to reduce stone recurrence than any other treatment.

“Without question, increased intake of water and clear fluids is the primary—and most effective—way to try to prevent formation of more kidney stones,” says Juan C. Calle, MD, FASN, Kidney Stone Clinic Medical Director.

Nephrolithiasis patients should aim for at least 2.5 to 3.0 liters of urinary output daily, says Dr. Calle. Dietary adjustments can help, too. The heart-healthy DASH diet has been shown to reduce risk of stone formation. So has decreased intake of foods high in oxalate, a core component of the calcium-oxalate crystalline compound that composes about 80 percent of all stones.

Counterintuitively, calcium reduction may promote stone formation, and doctors should encourage patients to continue consuming calcium-rich foods, Dr. Calle notes. Evidence suggests that when consumed together, calcium may bind with oxalate in the upper gastro-intestinal tract and pass through stool before these compounds can reach the kidneys and cause nephrolithiasis. In a study conducted by Cleveland Clinic nephrologists, 24-hour metabolic analysis showed significant changes in urinary calcium and oxalate excretion with vitamin D supplementation, suggesting a possible protective effect.

When water can’t cut it

Almost half of patients (35-50 percent) will experience a second stone within five years, and the risk increases if left untreated.

“It is important to remember that kidney stones are considered a chronic disease and therefore require ongoing surveillance and management,” says Dr. Calle. “When patients encounter a second stone formation, I almost always recommend they see a nephrologist to make sure no other associated diseases are a causative or complicating factor.”