Calcium-oxalate stones and uric acid stones are the two types of kidney stones affected by diet. These types of stones form because of excess calcium, oxalate or urate (uric acid) in the urine. The National Institutes of Health (NIH) says changes in diet and medication can help prevent kidney stones.
Sodium
According to the NIH, high sodium levels in the urine are related to high calcium levels. When calcium is high, there is a greater chance that it will bind with oxalate and form calcium-oxalate stones. Reducing sodium (salt) in the diet can prevent elevated calcium levels and subsequent kidney stones and is preferred over limiting dietary calcium. Kaiser Permanente recommends eating more fresh foods and less processed foods such as canned foods, fast foods, hot dogs, deli meats and salty snacks to reduce dietary sodium. Individuals monitoring their sodium intake should also refrain from adding salt to foods during cooking and at the table. Ingredients that contain sodium include MSG, sodium bicarbonate (baking soda), baking powder, sodium nitrate, sodium nitrite and disodium phosphate.
Oxalate
A high-oxalate diet can increase the risk of calcium-oxalate stones. The foods containing the most oxalate include rhubarb, nuts, spinach, wheat bran, beets, tea, chocolate and strawberries. Other high-oxalate foods 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, eggplant, black pepper, marmalade and soy sauce. Beverages with oxalate include coffee, chocolate milk and hot chocolate, dark beers, black tea, soy drinks and juices made out of high-oxalate fruits.
Meat and Alcohol
High-protein foods such as meat and seafood increase calcium and oxalate in the urine, according to Kaiser Permanente. Meat also contains purine, a substance that gets converted to uric acid. The NIH advises people with kidney stones or at risk for kidney stones to limit themselves to 6 ounces of meat a day. High-purine foods include organ meats, sweetbreads, liver, kidney, brain, meat extracts and broths, meat gravies, anchovies, sardines, herring, mackerel and scallops.
According to the NIH, alcohol contains purines, but moderate intake does not appear to increase the risk of kidney stones. Moderate intake is defined as less than two drinks a day; one drink is equivalent to 12 ounces of beer, 5 ounces of wine or 1½ ounces of hard liquor.
Additional Foods
Jackson Seigelbaum Gastroenterology says consuming foods with lots of added sugar increases the risk of calcium-oxalate kidney stones. According to the University of Maryland Medical Center (UMMC), fruits and vegetables, high-fiber foods and magnesium-rich foods might help reduce symptoms of kidney stones. The NIH also recommends limiting grapefruit juice, dark-colored colas and cranberry juice.
Herbs and Supplements
Herbs and supplements might help prevent kidney stones; however, the successes of many are based on anecdotal evidence without scientific proof. The UMMC recommends consulting a physician before treating kidney stones with alternative therapies. Herbs that might help kidney stones include cranberry, green tea, milk thistle and relora. Supplements that might reduce symptoms of kidney stones include multivitamins, magnesium citrate, omega-3 fatty acids, IP-6, N-acetyl cysteine, grapefruit seed extract and lactobacillus acidophilus.
References
- Jackson Seigelbaum Gastroenterology: Kidney Stone Diet
- Kaiser Permanente: Dietary Guidelines for Kidney Stones
- National Kidney and Urologic Diseases Information Clearinghouse: Diet for Kidney Stones
- University of Maryland Medical Center: Kidney Stones
- University of Pittsburg Medical Center: Low Oxalate Diet
