Question

My husband has had 2 kidney stones in the past year. He is 42 years old and very healthy otherwise. The doctor's recommendation is of course to consume large quantities of water daily. He is also advised to limit the following: green leafy vegetables (due to the oxylates), sweet potatoes, animal protein (does this include poultry and fish?), chocolate, and nuts. I have always been nutrition conscious with the entire family so the vegetable limitations are troublesome. Broccoli and spinach were frequently on our menu. Please suggest healthful ways to live within these guidelines and any other helpful information on kidney stones. Thanks.

Answer

Kidney stones are more common than you might realize. About 10% of men and 5% of women develop kidney stones. Kidney stones are formed when the concentration of components in the urine reach a level in which they crystallize. About 80% of stones are composed of calcium oxalate and are most common in middle-aged men. There are a variety of causes for this type of stone and your husband should be working with his healthcare provider to determine what the source may be. Family history is also an important factor. Regardless of the stone components, drinking at least 10 glasses of fluid/day (half from water) or enough to produce about two and a half quarts of urine/day is an essential component of prevention. The goal of increasing fluid intake is to dilute the urine, preventing the crystallization of stone-forming minerals. Drinking before bed is important to decrease the concentration of the urine at night to prevent crystallization. The current dietary recommendations for calcium oxalate stones include: 1. Consuming a diet adequate in calcium, about 800 – 1200 mg/day. Calcium binds with the oxalate to prevent its absorption. Food sources of calcium are recommended over supplements. Do NOT restrict calcium just because the stones are calcium oxalate. Research indicates this is not appropriate. (Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria. N Eng J Med, 2002, vol. 346, pp. 77—84). 2. Moderating protein intake to the RDA, which is about 60 grams/day for men and 50 grams/day for women. No more than half should come from animal sources which includes beef, pork, chicken and fish. (1 ounce of meat contains 7 grams of protein.) 3. Limiting sodium to 3 grams/day. To keep sodium to this level, avoid using salt and avoid high sodium foods such as canned soups, lunchmeats, frozen meals, etc. 4. Limiting high oxalate foods, specifically rhubarb, spinach, strawberries, chocolate, wheat bran, nuts, beets and tea. (see Url 1 below) Note the term is limiting and not eliminating. This means you can occasionally choose from the foods high in oxalate but need to control portion size. Including calcium- containing foods with the high oxalate foods may also decrease the absorption of the oxalate. The guidelines above and the list of foods high and low in oxalates will make it easier to enjoy a balanced diet for your family while helping the individual prone to kidney stones. Moderation is the key. Include grains, a variety of fruits and vegetables, plant sources of protein and dairy products. You can include animal protein to a maximum of about 3 ounces a day. Dr. Irene

For More Information

Oxalate content of foods