the kidney and increases the risk of stones.9 When people cut their salt (sodium chloride) intake in half, they reduce their daily need for calcium by about 160 milligrams.15Plants of any kindgrains, vegetables, legumes, and fruitscontain almost no sodium at all unless it is added during canning or other processing. Dairy products and meats contain more salt than plant products, and table salt, frozen meals, and canned and snack foods are the highest-sodium food products. For more information, see the sodium/potassium chart in Section 5.Sugar. Sugar accelerates calcium losses through the kidney.16 In the Nurses Health Study, those who consumed, on average, 60 grams or more of sugar (sucrose) per day had a 50 percent higher risk of stones than those who consumed only about 20 grams.9SUGAR IN COMMON FOODS (grams)Candy bar (2 ounces)22-35Cookies (3)11-14Corn flakes (1 cup, 28 grams)2Frosted corn flakes (1 cup, 41 grams)17Crackers (5)1Fruit cocktail (1/2 cup, 124 grams)14Grape jam (1 tablespoon)13Ice cream (1/2 cup, 106 grams)21Soda (12 ounces)40White bread (2 slices)1Source: package informationClimate. Kidney stones are also more common in warm climates, presumably because perspiration leads to dehydration and a more concentrated urine, and because sunlight increases the production of vitamin D in the skin which, in turn, increases calcium absorption from the digestive tract.17Surprisingly, oxalate-rich foods, such as chocolate, nuts, tea, and spinach, are not associated with a higher risk of renal stones,7 nor is vitamin C, even though it can be converted to oxalate. A large study of men taking vitamin C supplements found that they had no more kidney stones than men who do not take them.8Helping Patients Avoid Kidney StonesHere are simple steps to help your patients avoid kidney stones.Encourage patients to drink plenty of water or other fluids, staying ahead of their thirst.Diets including generous amounts of vegetables, fruits, and beans are rich in potassium and very low in sodium.If you prescribe calcium supplements, encourage patients to take them with meals, rather than between meals.Encourage patients to avoid animal products. Their proteins and sodium content increase the risk of stones.Patients should keep salt and sugar use modest.Cranberry Juice: An Old Remedy Is Clinically TestedCranberry juice has long been used as a folk remedy for urinary infections. A 1994 report in the Journal of the American Medical Association showed that it does indeed have at least a preventive effect. In a test involving 153 elderly women in Boston, half the subjects drank 300 milliliters (about one and one-quarter cups) of cranberry juice cocktail each day, using the same bottled beverage that is commonly sold in grocery stores.18 The other subjects consumed a drink that looked and tasted like cranberry juice, but had no real juice in it.Over the next six months, urine samples were collected and tested for signs of bacteria. The women consuming cranberry juice had only 42 percent as many urinary infections as the control group. The number of cases that had to be treated by antibiotics was also only about half, which is a real advantage, since antibiotics can sometimes lead to yeast infections and other problems. It takes about four