Nephrolithiasis, or more commonly, kidney stones affect nearly 400,000 people a year according to Nutrition and Diagnosis-Related Care. Approximately 75 to 80 percent of stones are composed of calcium oxalate, with the remaining stones being composed of struvite, uric acid and a very small proportion from ammonium acid urate. The stones can be caused by medications, fluid status, metabolic disorders and food intake. Even though most stones are calcium oxalate, high oxalate foods are more likely the cause. Other dietary factors such as high sodium and caffeine are also associated with increased risk.
High Sodium Foods
High sodium in the diet causes excess calcium to be excreted in the urine, which can cause kidney stones. High sodium foods include anything with excess salt added for preservation or flavor such as processed foods, fried foods, deli meats, canned soups, frozen dinners and canned vegetables. Adding excess salt to foods can also cause dietary sodium to increase. Decreased sodium in the diet is associated with decreased risk for development of kidney stones, and most Americans should aim for a goal of less than 4g of sodium a day.
High Oxalate Foods
Since most stones are composed of calcium oxalate, it is recommended individuals who have high amounts in their urine restrict excess dietary oxalate, according to Mayo Clinic. High oxalate foods include rhubarb, spinach, beets, chocolate, wheat germ, soybean crackers, peanuts, okra, sweet potatoes and Swiss chard. Other foods that contain medium amounts of oxalate are grits, grapes, strawberries, celery, green peppers, red raspberries, fruit cake, liver and marmalade.
Other Important Factors
Diets high in animal protein, refined carbohydrates and salt can increase risk for developing kidney stones. Conversely, a balanced diet with moderate amounts of plant and animal protein is important for decreasing risk. Adequate calcium intake is also important for decreased risk for developing kidney stones and those who are at risk should try to get 1,000mg dietary calcium daily. Calcium supplements however, increase risk. Uric acid stone sufferers should decrease their dietary consumption of foods high in purines, sardines for example. Also, decreased fluid intake and high caffeine consumption is associated with an increased risk as well.
References
- National Institute of Health: Kidney Stones
- Mayo Clinic: Kidney Stones
- Escott-Stump, S. Nutrition and Diagnosis-Related Care. 2008.
