Kidney stones can be very painful. About 10 percent of people will experience them at some point of in their life, and nearly 70 percent will have them more than once. About 80 percent of kidney stones are made from calcium oxalate. Dietary changes can help reduce the occurrence and re-occurrence of these stones.
You might think that since calcium oxalate is made from calcium, decreasing your intake of calcium would help decrease your risk of stone formation. Overwhelming evidence indicates the opposite is true. As reported in the May 9, 2006 issue of "Canadian Medical Association Journal," men on a high-calcium diet had a significantly lower rate of stone recurrence than those following a low-calcium diet. The theory is that certain forms of dietary calcium bind to oxalate in your stomach, preventing its absorption in a form that leads to kidney stones. Foods containing high levels of calcium include milk and dairy products such as yogurt and fish. Although dark green leafy vegetables and nuts can be high in calcium, they should be avoided as they also contain high levels of oxalate, which does increase risk of stone formation.
In addition to high-calcium foods, foods low in sodium also decrease the risk of stone formation. When healthy kidneys process and excrete sodium, calcium often gets excreted along with it. Excessive consumption of sodium increases your calcium loss, increasing your risk of stone formation. There are many foods low in sodium, including most fruits and vegetables. Some fruits, such as strawberries, however, should be avoided due to their oxalate content. Processed foods can be high in sodium, so it's important to read labels. Low-sodium breads, canned beans, canned vegetables and soups are available. Keeping sodium intake to less than 2,000 mg per day is optimal.
A low-protein diet can decrease your risk of stone formation. Animal protein lowers citrate excretion and increases calcium and uric acid excretion. Limiting total protein intake to less than 80 g per day is recommended. Low-protein diets typically include small amounts of protein from animal and vegetable sources, such as fish, poultry, eggs, meat, and dairy products, which are considered high-quality, or complete, proteins, as well as vegetable sources, such as breads, cereals, rice, pasta, and dried beans. All of these are available in low-sodium versions.
While not technically a food, increasing fluid intake significantly reduces the occurrence and re-occurrence of calcium oxalate stones. The more liquid you drink, the more urine you make, the less likely you are to develop kidney stones. The type of fluid you drink has some bearing on your risk; drinking coffee and beer for example, decreases your risk of stone formation, while drinking grapefruit juice can significantly increase your risk.