Kidney stones are hard masses that form in the kidneys and can be painful. According to the National Institutes of Health, some foods form waste products that can become kidney stones. The most common types of kidney stones associated with food are calcium-oxalate stones and uric acid stones. The Cleveland Clinic reports that calcium-oxalate stones form when there is too much calcium, oxalate or urate in the urine and not enough citrate. Uric acid stones form when urine is too acidic and uric acid collects. Physicians can diagnose the type of kidney stone once it is excreted in the urine.
Sodium
According to the NIH, high levels of sodium or salt in the diet are associated with high calcium levels. Calcium-oxalate stones form when calcium binds to oxalate. The NIH reports that reducing sodium to prevent calcium from building up is preferred over limiting dietary calcium. The Cleveland Clinic and Kaiser Permanente advise people with kidney stones to eat more fresh foods and less canned, packaged, processed and fast foods. It is also important to cook with less salt and refrain from adding salt at the table. Other ingredients that should be avoided because they contain sodium include MSG, sodium bicarbonate, or baking soda, baking powder, sodium nitrate, sodium nitrite and disodium phosphate.
Oxalate Foods
The University of Pittsburgh Medical Center recommends that people with a tendency to form calcium-oxalate stones limit foods containing oxalate. Oxalate is in beverages like coffee, chocolate milk, dark beers, black tea, soy drinks and some fruit juices. It is also in nuts and nut butters, wheat bran, whole wheat flour, bran cereals, berries, rhubarb, figs, citrus peel, kiwis, tangerines, green leafy vegetables, okra, olives, beans, beets, potatoes and sweet potatoes, peppers and eggplant. Condiments and seasonings that contain oxalate include black pepper, marmalade, soy sauce and chocolate.
Meat
Meat is high in purines, which the body converts to uric acid. The NIH suggests that individuals with uric acid stones or those at risk for kidney stones limit themselves to less than 6 oz. of meat a day. Kaiser Permanente also recommends avoiding sweetbreads, organ meats like liver, kidney and brain, meat extracts and broths, gravy made from meat drippings, anchovies, sardines, herring, mackerel and scallops.
Additional Foods
Jackson Seigelbaum Gastroenterology advises avoiding foods with lots of added sugar because they may promote the formation of calcium-oxalate stones. Kaiser Permanente says to avoid taking more than 100 percent of the RDA for vitamin C a day. According to the NIH, the body can turn vitamin C into oxalate, and doctors usually recommend less than 500 mg of vitamin C a day for people with kidney stones. The NIH reports that alcohol may promote purine production, but moderate intake, defined as no more than two drinks a day, does not appear to increase the risk of kidney stones.
