Stop kidney stones. (Quick Studies).

Most people who get kidney stones made of calcium oxalate (the most common kind) excrete too much calcium in their urine. So for years, doctors have told them to cut back on calcium. Now a new study has shown that that advice was wrong. Eating less animal protein and salt works far better.

Over five years, 40 men who ate 50 grams of animal protein and 2,500 mg to 3,000 mg of sodium a day were half as likely to get another kidney stone as 28 men who were told to eat no more than 400 milligrams of calcium.

The lower-protein, lower-salt diet reduced both calcium and oxalate in the men's urine. In contrast, the lower-calcium diet reduced calcium, but increased oxalate (probably because there was too little calcium to bind the oxalate in the intestine).

What to do: If you've had a kidney stone made of calcium oxalate and you excrete excess calcium, limit your protein from meat, seafood, poultry, and milk, cheese, and other dairy products to about 50 grams a day. (The U.S. Recommended Daily Allowance for protein is 50 grams, and that includes protein from breads, cereals, beans, and other plant foods. So the 50-gram limit on animal protein isn't exactly a low-protein diet.)

And keep your sodium as close as possible to 2,400 mg a day (that's half what many Americans eat).

N. Eng. J. Med. 346: 77, 124, 2002