Ask the Doctor
Questions about kidney disease? Risk factors? Signs and symptoms? Are you concerned about yourself, a friend or family member? Ask Dr. Spry.
If you have kidney stones, you may need to follow a special diet. First, your doctor will run tests to find out what type of stones you form. From these, the doctor can determine which diet changes may be right for you. A registered dietitian can help you make the necessary changes in your diet.
A kidney stone is a hard mass that forms from crystals in the urine. In most people, natural chemicals in the urine stop stones from forming.
No. The most common types of kidney stones are made from calcium and oxalate. Individual treatment for kidney stones depends on the type of kidney stones that are formed.
Sometimes following a special diet may be enough to prevent you from forming more kidney stones. Other times, medications, in addition to a special diet, may be needed.
You may be asked to make changes to the amount of salt (sodium), calcium, oxalate, protein, potassium and fluid in your diet. A registered dietitian can help you with making these changes.
To lessen your risk of forming a new stone, it is very important that you drink at least three quarts (12 cups) of fluid throughout the day. In hotter weather, you may need to drink more to make up for fluid loss from sweating. This will help keep your urine less concentrated. Less concentrated urine reduces the risk of stone formation. Most of the fluid you drink should be water. Try to drink a glass of water before bed and if you wake during the night to use the bathroom, drink another glass before going back to bed.
If you have had a calcium stone, your doctor may ask you to cut back on the salt and sodium in your diet. Extra sodium causes you to lose more calcium in your urine, putting you at risk for developing another stone. Your doctor will probably advise you to limit sodium to 2,000 milligrams each day. There are many sources of “hidden” sodium such as canned or commercially processed foods as well as restaurant-prepared and fast foods. A dietitian help you understand food labels and make changes in the amount of sodium that you eat.
You may not need to avoid calcium in your diet. It is important that you learn from your doctor and dietitian the right balance of calcium to eat. Following a diet low in calcium for a long period of time can lead to a loss of bone mass, or osteoporosis. In general, you can include two to three servings daily of good sources of calcium such as milk products and cheese. Including a source of calcium at each meal may actually help prevent oxalate stones from forming as the calcium binds with oxalate in food and thus prevents the oxalate from being absorbed into the body. For a good source of calcium, choose ½ cup of milk, yogurt, pudding or ice cream or ¾ oz cheese.
Your doctor or registered dietitian can help determine if you need more or less calcium and help you plan a diet that is healthful.
If you have had a kidney stone that contains oxalate, research suggests that limiting high oxalate foods may help reduce your chance of forming another oxalate stone. The oxalate content of food can vary due to differences in such things as soil quality and state of ripeness. There may be variation in published data, too, as different methods may be used to determine the oxalate content of food.
Given these variables and the confusion that may be caused by comparing one available list with another, it is difficult to come up with an all-inclusive list of foods to avoid. However, as there is some agreement on the following foods, it is suggested that these foods be avoided as they are high in oxalate: peanuts, tree nuts (such as almonds, cashews, hazelnuts), soybeans, soy milk, wheat germ and wheat bran (including cereals), spinach, black tea, instant tea, rhubarb, beets, most dried beans (e.g., black, navy or Great northern), chocolate, and sweet potatoes. Based on a 24-hour urine collection study, your doctor may be able to give you guidelines on how strictly you need to avoid oxalate-containing foods. Many high oxalate foods are healthful so it is wise to not overly restrict your diet if not necessary.
Because the stone contains calcium and oxalate, be sure to follow the calcium recommendations from the last question.
Reducing the amount of animal protein may help. Sources of animal protein include beef, chicken, pork, fish and eggs. Most people need only four to six ounces of high protein foods and three servings of milk or cheese a day. Check with your doctor or dietitian to be sure your protein intake is enough, but not too much.
The B vitamins (which include thiamine, riboflavin, niacin, B6 and B12) have not been shown to be harmful to people with kidney stones. However, check with your doctor or dietitian for advice on the use of vitamin C, vitamin D, fish liver oils or mineral supplements containing calcium since some supplements can increase the chances of stone formation in some people.
Massey, LK. Food Oxalate: Factors Affecting Measurement, Biological Variation, and Bioavailability. JADA. 2007: 107(7): 1191-1194.
Nutrition Therapy for Kidney Stones. ADA Nutrition Care Manual. American Dietetic Association. Content release date October 4, 2010.
The Oxalate Content of Foods 2008. The Oxalosis and Hyperoxaluria Foundation. http://www.ohf.org/diet.html
Last updated September 2011
The National Kidney Foundation would like to thank the
Council on Renal Nutrition for the development of this fact sheet.
If you would like more information, please contact us.
©2013 National Kidney Foundation. All rights reserved. This material does not constitute medical advice. It is intended for informational purposes only. No one associated with the National Kidney Foundation will answer medical questions via e-mail. Please consult a physician for specific treatment recommendations.