There are two types of kidney stones that are associated with diet: calcium-oxalate stones and uric acid stones. The Cleveland Clinic states that these stones form due to an excess amount of calcium, oxalate or urate (uric acid) in the urine. Physicians can diagnose the type of stone, and according to the National Institutes of Health (NIH), dietary changes in addition to medication can help prevent kidney stones.
Sodium
The NIH states that high sodium levels in the urine are associated with high calcium levels. Higher concentrations of calcium increase the potential for calcium to bind with oxalate and form calcium-oxalate stones. Reducing dietary sodium prevents calcium buildup and is preferred over limiting dietary calcium, according to the NIH. Kaiser Permanente advises people to eat more fresh foods and limit canned, processed, packaged and fast foods like hot dogs, deli meats and salty snacks. Cooking with less salt, and refraining from adding salt at the table will also reduce dietary sodium. The NIH also points out that MSG, sodium bicarbonate (baking soda), baking powder, sodium nitrate, sodium nitrite and disodium phosphate contain sodium and should be limited or avoided.
Foods with Oxalate
Foods with oxalate should be limited or avoided by people who form calcium-oxalate stones. According to the University of Pittsburgh Medical Center, a low-oxalate diet contains 40 to 50 mg of oxalate a day. The foods with the most oxalate are rhubarb, nuts, spinach, wheat bran, beets, tea, chocolate and strawberries. High-oxalate beverages include coffee, chocolate milk and hot chocolate, dark beers, black tea, soy drinks and juices made out of high-oxalate fruits. Other foods that contain oxalate are 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 and eggplant. Condiments like black pepper, marmalade and soy sauce also contain oxalates.
Meat and Alcohol
According to Kaiser Permanante, high protein foods increase the amount of calcium and oxalate in the urine. Meat, especially organ meats, contains purines that get converted into uric acid. The NIH advises individuals with a history of uric acid stones to eat less than 6 oz. of meat a day. Specific foods high in purines include sweetbreads, liver, kidney, brain, meat extracts and broths, meat gravies, anchovies, sardines, herring, mackerel and scallops.
Alcohol contains purines, but according to the NIH, moderate alcohol, defined as less than two drinks a day, does not appear to increase kidney stone formation. One drink equals 12 oz. of beer, 5 oz. of wine, or 1.5 oz of hard liquor.
Additional Foods
Vitamin C and D supplements may aggravate kidney stones. According to the NIH, vitamin C can be converted into oxalate, and most doctors recommend less than 500 mg of vitamin C per day for people with a history of kidney stones. Jackson Seigelbaum Gastroenterology states that added sugar can increase the risk of calcium-oxalate kidney stones. They recommend avoiding products with lots of added sugar, but state that naturally-occurring sugars do not appear to affect kidney stones. Other beverages that should be avoided according to the NIH include grapefruit juice, dark-colored colas and cranberry juice.
