In 1986, more than 2 billion dollars was spent on the treatment of kidney stones. Since kidney stones are commonly composed of calcium oxalate and calcium phosphate, conventional wisdom says that to prevent the formation of calcium-containing kidney stones, dietary calcium should be reduced. Until recently no studies had been done examining the validity of this advice. Dr. Gary Curhan and co-investigators at Harvard studied more than 45,000 men for four years. The authors speculate that increased dietary calcium may reduce the absorption of oxalate.
Oxalate is also a culprit in kidney stone formation.
If less was absorbed, less would be available to form stones. Readers who want to reduce their risk of kidney stones should not rely on calcium supplements. In the Harvard study, they did not have the same protective effect as did dietary calcium, for unknown reasons. Dairy products are not necessarily the best way to prevent kidney stones. In this study, high animal protein intakes were found to increase risk of kidney stones.