There are many types of kidney stones but the ones most commonly associated with diet are calcium-oxalate stones and uric acid stones, which form due to an excess of calcium, oxalate and uric acid in the urine. According to an informatoin website produced by Jackson Seigelbaum Gastroenterology in central Pennsylvania, drinking enough fluids is one of the most important ways to prevent kidney stones. The site advises people with kidney stones to drink 8 to 10 oz. of fluid every hour that they are awake. Avoiding certain foods and taking medications can also help prevent kidney stones, according to the National Institutes of Health.
Sodium
Jackson Seigelbaum Gastroenterology says reducing dietary sodium appears to reduce the amount of calcium in the urine. Too much calcium in the urine increases the potential for calcium-oxalate stones to form. The NIH recommends limiting sodium to 2,400mg a day, which is the same guideline for healthy individuals. Kaiser Permanente encourages people to focus on fresh foods while limiting canned, processed and fast foods. High-sodium foods include deli meats and hot dogs, chips, crackers, frozen dinners, pretzels, cheese, olives, salted nuts, instant soups, pasta and rice mixes and some condiments. The NIH also recommends limiting sodium-containing ingredients like MSG, sodium bicarbonate, or baking soda, baking powder, sodium nitrate, sodium nitrite and disodium phosphate.
Oxalate
Oxalate, or oxalic acid, is in plant foods and combines with calcium to form calcium-oxalate stones. According to Jackson Seigelbaum Gastroenterology individuals on a low-oxalate diet should consume less than 50mg of oxalate a day and limit foods high in oxalate. The foods with the most oxalate and known to aggravate kidney stones include rhubarb, spinach, strawberries, chocolate, wheat bran, nuts, beets and tea. High-oxalate beverages include coffee, chocolate drinks, dark beers, soy drinks and juices from high-oxalate fruits. Other oxalate foods identified by the University of Pittsburgh Medical Center include grits, whole wheat flour, bran cereals, berries, figs, citrus peels, kiwis, tangerines, green leafy vegetables, okra, olives, beans, parsley, zucchini, potatoes and sweet potatoes, peppers, eggplant, black pepper, marmalade and soy sauce.
Meat and Alcohol
Meat contains purines, which get converted into uric acid. Kaiser Permanente also says high-protein foods increase the amount of calcium and oxalate in the urine. Individuals with a tendency to form uric acid are advised by the NIH to limit their meat intake to 6 oz. a day. High-purine foods include sweetbreads, liver, kidney, brain, meat extracts and broths, meat gravies, anchovies, sardines, herring, mackerel and scallops.
Alcohol contains purines and is usually prohibited on a low-purine diet but, according to the NIH, moderate alcohol use does not appear to increase the formation of kidney stones. Moderate alcohol intake is defined as less than two drinks per day where one drink is equal to 12 oz. of beer, 5 oz. of wine or 1.5 oz. of hard liquor.
Additional Foods
According to Jackson Seigelbaum Gastroenterology, added sugar can increase the risk of calcium-oxalate kidney stones. The gastroenterology practice recommends avoiding foods with lots of added sugar, but says that naturally occurring sugars do not affect kidney stones. The NIH says other beverages that should be avoided because they increase the risk of kidney stones include grapefruit juice, dark colas and cranberry juice.
