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Low-salt, low-protein diet can prevent kidney stones

A diet low in salt and meat can dramatically reduce the risk of kidney stones, according to an Italian study that could spell the end for the low-calcium diet that doctors have been recommending for years.

About 10% of the U.S. population - and a much larger percentage of men, who make up 80% of sufferers - will have at least one kidney stone sometime in their lives, and it can be excruciatingly painful. Most stones can be excreted, but in about 15% of cases, surgery or shockwave treatment to pulverize the stones is needed.

Many doctors have told such patients to cut down on calcium because most kidney stones are made of a calcium compound. But recent studies have suggested that such a diet might not prevent kidney stones after all and may even promote them - along with osteoporosis.

The new study "dispelled a myth that a low-calcium diet is important in preventing kidney stones," said Dr. David A. Bushinsky, a kidney specialist at the University of Rochester.

William Keane, president of the National Kidney Foundation, said he is sure the new diet "will become the gold standard."

Dr. Umberto Maggiore, explained that people on a low-calcium diet excrete less calcium in their urine but more of the other substance that combines with calcium to form most kidney stones.

In addition, salt and one protein common in meat lead to more calcium in the urine, which in turn contributes to the formation of kidney stones, Bushinsky said.

The low-salt, low-protein diet allowed 2,900 milligrams of salt per day; 2,400 is the maximum recommended by the American Heart Association. But people were allowed only about three-quarters of an ounce of meat per day, with just over an ounce of cheese or other dairy protein.

The American Foundation for Urologic Disease does not mention a low-calcium diet on its Web page about kidney stones, but does say a doctor may suggest a low-meat, low-salt diet. The National Kidney Foundation's Web page says a doctor may suggest either diet, depending on test results.

Health care for kidney stones added up to $1.8 billion in 1993, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Drinking 10 to 12 big glasses of water during the day can keep stones from forming and push out those smaller than a pea.