Anyone who has had kidney stones should try to prevent a recurrence. Some general prevention tips include:
- Increase fluid intake, restrict sodium, and reduce protein intake
- Get more potassium
- Try to correct any dietary habits that cause acid or alkaline imbalances in the urine, which promotes stone formation
Eating a high-calcium diet does not appear to increase the risk for kidney stones, as long as the diet also contains plenty of fluids, potassium, and phosphate. (Increasing calcium alone may pose a modest risk for stones.)
Because different kidney stone types may require specific dietary changes, patients should work with their doctors to develop an individualized plan. Nutritional considerations are very important in preventing recurrences, and patients should comply with the proper diet.
Fluids (Water, Juice, and Other Beverages)
Of all the preventive recommendations, drinking enough fluids is the most important guideline for people with any type of kidney stones.
- In general, patients with calcium or uric acid stones should drink at least 10 full glasses of fluid each day (at least half should be water). They should drink one glass with each meal and drink fluids at night, even if they have to get up during the night to go to the bathroom. Fluid intake should produce at least two-and-a-half quarts of urine each day.
- To prevent cystine stones, patients should drink even more water -- more than a gallon, or 16 8-ounce cups, every day. Patients should drink this amount at regular intervals throughout the day and night.
In all cases, patients need more fluid after exertion and during times of stress. If they drink enough, the urine should be pale and almost watery, not dark and yellow.
Water. Water hardness (meaning how much calcium is in the water) generally plays only a small role in stone formation. By far, the amount of fluid intake is most important in preventing stones.
Juices. Other beverages have various effects, depending on the type of stone:
- Lemon Juice: Drinking one-half cup of pure lemon juice (enough to make 8 glasses of lemonade) every day raises citrate levels in the urine, which might protect against calcium stones. (While orange juice also increases citrate levels, it does not lower calcium and it raises oxalate levels. Therefore, it is not recommended.)
- Cranberry and Apple Juice: Apple and cranberry juice contain oxalates, and both have been associated with a higher risk for calcium oxalate stones. Cranberry juice has properties that may increase the risk for both calcium oxalate and uric acid stones. On the other hand, cranberry juice helps prevent urinary tract infections, so it may be helpful for reducing the risk for struvite and brushite stones. (However, these stones are far less common.)
- Grapefruit Juice: Several studies have found that drinking grapefruit juice might increase the risk for stones.
Other Beverages and Their Effects on Stone Formation.
- Soft Drinks.Patients with stones should avoid cola drinks that contain phosphoric acid, because they can severely reduce citrate levels in the urine. However, citrus-based sodas (such as 7 Up and Sprite) are high in citrate, which might help prevent stones from forming, particularly in patients with low citrate in their urine, or who have a tendency to form uric acid stones.
- Alcohol. Wine may protect against kidney stones. However, it is important to remember that beer and other alcoholic beverages also contain purines, which may increase the risk for the less common uric acid stones in susceptible people. Binge drinking increases uric acid and the risk for stones.
- Coffee and Tea. Some research has reported a lower risk for stones in people who drink tea and both regular and decaffeinated coffee.
Low-Salt and Low-Protein Diets
A low-sodium, low-to-moderate protein diet containing normal levels of calcium can help reduce the recurrence of stones compared to a low-calcium only diet.
Salt Restriction. Because salt intake increases the amount of calcium in urine, patients with calcium stones should limit their sodium intake to 1,500 mg or less a day. Sodium may also increase levels of urate, the crystalline substance that can trigger the formation of recurrent calcium oxalate stones.
Protein Restriction. Protein increases uric acid, calcium, and oxalate levels in the urine, and reduces citrate levels. Diets high in protein, particularly meat protein, have been consistently connected with kidney stones. (Meat protein has a higher sulfur content and produces more acid than vegetable protein.)
Whether restricting meat protein alone without restricting sodium has any protective value is unknown. Most studies to date have found no difference in stone development between people with low and normal protein diets.
Although the precise role of dietary protein in kidney stones needs further clarification, it is reasonable for everyone to consume meat protein in moderation. People with struvite stones who need to reduce phosphates in their diets should also cut down on protein.
DASH Diet. The same diet that is recommended to control blood pressure might also reduce the risk of kidney stones. The DASH diet, which is high in fruits and vegetables and low in animal protein, appears to reduce the incidence of kidney stones by as much as 40 to 50%.
Role of Calcium
Calcium from Foods. Dietary calcium recommendations for kidney stone prevention need to be determined on an individual basis. A doctor will suggest calcium guidelines based on a patient's age, gender, body size, and type of stone. General recommendations for daily dietary calcium intake are: 1,300 mg for teenagers, 1,000 mg for men and women ages 19 to 50, and 1,200 mg for women after age 50 and men after age 70. Most studies indicate that people who eat the recommended amount of dietary calcium (found in milk, yogurt, and cheese) have a lower chance of stone recurrence than those who eat a low-calcium diet. Therefore, a diet containing a normal amount of calcium, but reduced amounts of animal protein and salt may protect against stones better than a low-calcium regimen.
Calcium Restriction in Certain Cases. Some patients, such as those whose stones are caused by genetic defects in which the intestine absorbs too much calcium, may need to limit calcium intake. More studies are needed to define this group precisely.
Fiber-Rich Foods and Their Compounds
Fiber may be beneficial for people with kidney stones. In addition, some fiber-rich foods may contain compounds that help protect against kidney stones. A wide variety of high-fiber plant foods contain a compound called phytate (also called inositol hexaphosphate, InsP6, or IP6), which appears to help prevent the crystallization of calcium salts, both oxalate and phosphate. Phytate is found in legumes and wheat and rice bran. (Soybeans are also rich in phytate, but they are also very high in oxalates, so the overall effects of soy on kidney stones are not clear.)
Purine Restriction in People at Risk for Uric Acid Stones
A high intake of purines can increase the amount of uric acid in the urine. Those at risk for uric acid stones should reduce their intake of foods and beverages that contain purines.
Some diet and lifestyle changes that may help prevent uric acid stones:
- Avoid alcohol, anchovies, sardines, oils, herring, organ meat (liver, kidney, and sweetbreads), legumes (dried beans and peas), gravies, mushrooms, spinach, asparagus, cauliflower, and baking or brewer's yeast.
- Limit how much meat you eat at each meal.
- Avoid fatty foods such as salad dressings, ice cream, and fried foods.
Oxalate Restriction in Hyperoxaluria
People who have hyperoxaluria will be advised to limit the amount of oxalate in their diet.
- Foods high in oxalic acid include beets, soy, black tea, chenopodium, chocolate, cocoa, dried figs, ground pepper, lamb, lime peel, nuts, parsley, poppy seeds, purslane, rhubarb, sorrel, spinach, and Swiss chard.
- Foods containing moderate amounts of oxalates include beans (green and wax), blackberries, blueberries, carrots, celery, coffee (roasted), concord grapes, currants, dandelion greens, endive, gooseberries, lemon peel, okra, green onions, oranges, green peppers, black raspberries, strawberries, and sweet potatoes.
Role of Fats
Certain fats may play a beneficial or harmful role in specific cases of kidney stones.
Restricted Fats in Patients with Stones Associated with Bowel Disease. Patients who have stones associated with short-bowel syndrome should eat foods with lower amounts of fats and oxalates. If patients with short-bowel syndrome eat too much fat, calcium may bind to unabsorbed fat instead of to oxalates, increasing oxalate levels and raising the risk of stone formation.
Fish Oil. Omega-3 fatty acids, found in oily fish like mackerel, salmon, and albacore tuna, have many health benefits, but the most current evidence suggests they do not help prevent kidney stones.
Role of Vitamins
Vitamin B6. Vitamin B6, or pyridoxine, is used to treat people with primary hyperoxaluria, a severe inherited disorder. Patients should not try to treat themselves with vitamin B6. Very high doses (500 to 2,000 mg daily over long periods of time) can cause nerve damage. Food sources of vitamin B6 include meats, oily fish, poultry, whole grains, dried fortified cereals, soybeans, avocados, baked potatoes with skins, watermelon, plantains, bananas, peanuts, and brewer's yeast.
Vitamin C. Ascorbic acid (vitamin C) may change in the body to tiny crystals, called oxalates. These crystals do not dissolve. People with hyperoxaluria (too much oxalate in the urine) should avoid vitamin C supplements. Even for men with normal oxalate levels, higher consumption of vitamin C (more than 1,000 mg a day) may increase kidney stone risk.
Healthy weight loss can help improve kidney stone management. Extreme diets with rapid weight loss and selective food intake however can have the opposite effect. Patients should work with their physician on the most appropriate diet for their type of kidney stone(s).
Stress Management Techniques
Because of an association between stress and kidney stones, relaxation and stress management techniques may also be beneficial.
Dietary Considerations. People with kidney stones appear to be more sensitive to certain foods than people who do not form kidney stones. Therefore, vulnerable people should make specific changes in their diet. They should work with their doctors to develop a dietary plan that fits their individual situation. Drinking plenty of fluids is important for preventing a recurrence of any kidney stone.
Indications for Drug Treatments. If dietary treatments fail, drug therapy may be helpful. A number of drugs are available to prevent recurrences of calcium oxalate and other stones. Medications that inhibit the formation of stones include allopurinol, thiazide, potassium citrate, and potassium-magnesium citrate. In addition, drug treatments can sometimes help prevent other complications related to stones, such as osteoporosis.
Correcting Underlying Conditions Known to Cause Kidney Stones. It is also important to treat and correct, if possible, any underlying disorder that may be causing stones to form. Such disorders include distal renal tubular acidosis, hyperthyroidism, sarcoidosis, and certain cancers. To prevent calcium stones that form in hyperparathyroid patients, a surgeon may remove the affected parathyroid gland (located in the neck).