Dietary Recommendations for Prevention of Kidney Stones

Dietary Recommendations for Prevention of Kidney Stones

“As a urologist practicing in Miami, Florida I tend to see a lot of patients with kidney stones. I am often asked by patients about dietary recommendations to prevent kidney stones.  I have attached recent recommendations by the National Kidney Foundation that may be helpful.” David Robbins, MD Urological Consultants of Florida

Diet and Kidney Stones

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.

What is a kidney stone?

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.

Are all kidney stones the same?

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.

Is there a diet I can follow to prevent me from having more kidney stones?

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.

What kind of diet will I have to follow?

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.

My doctor told me to drink a lot of fluids. How much is “a lot”? Does it matter what kind of fluid I drink?

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.

I had a calcium stone. What type of diet should I follow? Will I have to avoid high calcium foods?

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.

I had an oxalate stone. What type of diet should I follow? Do I need to avoid foods high in oxalate?

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.

Is there anything else I can do with my diet to help prevent kidney stones?

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.

Will it help/hurt me to take a vitamin or mineral supplement?

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.

Last updated April 2011

2,250-Year-Old Mummy Had Prostate Cancer

2,250-Year-Old Mummy Had Prostate Cancer Researchers find telltale signs of modern day man killerBy Greg Wilson | Wednesday, Nov 2, 2011 |

An ancient Egyptian had prostate cancer, according to recent testing. advertisement Testing on a 2,250-year-old mummy proves prostate cancer is nothing new. A mummy at the National Archaeology Museum of Lisbon had a pattern of tumors between its pelvis and lower spine, telltale signs of the modern day man killer. “The bone lesions were considered very suggestive of metastatic prostate cancer,‭” ‬researchers wrote in a paper on the mummy published in the International Journal of Paleopathology. The man beneath the gauze wrapping was between 51 and 60 years old when he died around 285 B.C. The mummy was analyzed by a powerful Multi-Detector Computerized Tomography scan. Researchers believe the man died a slow and painful death. “It is the oldest known case of prostate cancer in ancient Egypt and the‭ ‬second-‬oldest case in history,‭” ‬radiologist and researcher Carlos Prates said. Paula Veiga, an Egyptologist, told Discovery News the case proves that cancer, believed to be largely environmental, existed in ancient Egypt. “This study shows that cancer did exist in antiquity,‭ ‬for sure in ancient Egypt.‭ ‬The main reason for the scarcity of examples found today might be the lower prevalence of carcinogens and the shorter life expectancy,‭” ‬said Veiga The earliest known case of prostate cancer was found in ‬2007,‭ ‬by researchers investigating the skeleton of a‭ ‬2,700-year-old Scythian king who died in Siberia.

Survey of Top Doctors Finds Widespread Support for PSA Screening



Survey of Top Doctors Finds Widespread Support for PSA Screening

Top Doctors strongly disagree with government task force proposal to drop use of prostate cancer test

October 28, 2011 RSS Feed Print


PSA screening for prostate cancer has been a hot topic in the urology news not only for patients in Miami, but throughout the country.  The U.S. Preventive Services Task Force’s decision to downgrade the recommendation for PSA screening for prostate cancer has not been supported by the either polled urologists or primary care physicians.  This article highlights topics and opinions in the current debate over PSA screening for prostate cancer.”

In an exclusive new survey of Top Doctors conducted by U.S. News & World Report, virtually all responding urologists and more than 60 percent of internal-medicine specialists rejected the recent proposal by a high-level government advisory committee to end routine PSA testing, which is meant to catch prostate cancer early.

An estimated 20 million men a year undergo PSA screening, which determines the blood level of a protein called prostate-specific antigen; nearly 250,000 of them are diagnosed with prostate cancer. The proposal, issued by the U.S. Preventive Services Task Force, advises doctors not to screen patients with the PSA test unless they have symptoms that are “highly suspicious” for prostate cancer.

“If you argue that you should not use PSA testing at all in [men without symptoms], you’re essentially saying you don’t want to find prostate cancer at a curable stage,” says Dr. Samir S. Taneja, director of urologic cancer at NYU Langone Medical Center and a responder to last week’s U.S. News survey.

The government task force found little evidence that screening men with the PSA test significantly reduces deaths from prostate cancer. Whatever small benefit there might be, the task force concluded, is outweighed by the risk of an incorrect diagnosis or unnecessary procedure leading to death or complications. About a third of men treated for prostate cancer suffer urinary incontinence, impotence, or both, and about 1 in every 200 dies within 30 days from complications of surgery.

Doctors have debated the risks and benefits of the PSA test since 1994, when the Food and Drug Administration approved it for cancer screening. Even the test’s supporters acknowledge that it is inherently imprecise. A high PSA level may indicate the presence of a tumor—or it may not. Nor is a low PSA level necessarily an all-clear. Moreover, the test cannot distinguish between a typical tumor, which grows so slowly that the threat is minimal, and one that is aggressive and potentially lethal.

To determine whether some of the nation’s best doctors agree with the task force’s proposed recommendation, U.S. News surveyed more than 600 urologists and internists who are recognized as Top Doctors by U.S. News and Castle Connolly Medical Ltd. More than a third of the physicians responded. (For a breakdown of the questions and responses, see Behind the U.S. News Top Doctors Survey on PSA Screening.)

About 95 percent of the responding urologists felt that doctors should continue to advise men starting at age 50, when testing typically begins, to have PSA screenings as part of a routine physical exam, contrary to the task force’s recommendation. They included themselves in that group; 97 percent indicated they would be tested starting at 50. The internists were less unanimous—about 40 percent agreed with the proposed recommendation to end routine testing. But 72 percent of the responding male internists indicated that they themselves would have the test starting at age 50.

The vast majority of the survey respondents sent U.S. News comments as well. “Can you put a price on being saved from dying of cancer?” wrote Dr. Ernest H. Agatstein, a urologist with Paletz Agatstein Urology Medical Group in Downey, Calif.

PSA screening is “an awesome test,” wrote Dr. Richard J. Macchia, a urologist at Cleveland Clinic Florida in Weston. “When I was young,” he went on, “almost all the prostate cancer patients I saw had metastatic disease at diagnosis. Now, in patients who have their PSAs checked, I almost never see metastatic disease at the time of diagnosis. We can cure metastatic diseases only rarely.”

Task force member Dr. Michael LeFevre, professor of family medicine at the University of Missouri School of Medicine in Columbia, says the impassioned backlash against the draft task force recommendation is unsurprising. “When science doesn’t give us the result we want, it’s pretty unusual for the medical and patient communities to turn on a dime and say, ‘We were wrong,’ ” he told U.S. News.

The task force reviewed over 8,000 summaries of research studies related to prostate cancer screening and treatment. Many were eliminated because of major flaws. The strongest evidence came from two large trials that examined the impact of prostate cancer screening on death rates.

The first was a U.S. trial of nearly 80,000 men between the ages of 55 and 74. The men were divided into two groups: One had PSA testing and a digital rectal exam and the other had only a rectal exam. The study found that screening boosted the number of diagnosed cancers by 20 percent, but also that diagnosing the additional cancers did not reduce overall death rates over 10 years of follow-up.

The second study, involving 182,000 men and carried out in Europe, found that PSA screening reduced the number of cancer deaths by about 6 or 7 for every 10,000 men tested. Based on these results, the task force concluded, 48 men would have to be treated to prevent one prostate cancer death, exposing 47 men to the dangers of treatment.

Dr. Patrick Walsh of Johns Hopkins Hospital, a pioneer of radical prostatectomy—surgical removal of the entire prostate gland—takes issue with the task force assessment. He points to American Cancer Society statistics that show a 40 percent decrease in prostate cancer deaths since 1994, a decline that he attributes to the introduction of PSA screening.

Dr. LeFevre counters that the downward trend in prostate cancer deaths began before the PSA test was widely adopted, which suggests that the test wasn’t the driving force.

Dr. Alan Wein, chief of urology at the Hospital of the University of Pennsylvania, told U.S. News in an interview that the two sides may not be as far apart as they seem. On the one hand, he says, “mortality from prostate cancer has decreased, and it happens to coincide with PSA screening. And there’s no question that, before PSA screening, it was common to see people come in with metastatic or very advanced local disease. You rarely see that now. It may not be cause and effect, but those are the facts.”

On the other hand, says Wein, there’s also no question that too many patients are encouraged to seek radical prostatectomy or radiation and too few are informed about a third option known as watchful waiting, in which doctor and patient use periodic PSA tests, frequent physical exams, and biopsies to track a tumor’s growth and decide when, if ever, to pursue aggressive treatment.

“I would hope that the whole issue helps urologists understand that we have to be forthright with patients about our expectations for treatment and those circumstances when it’s most reasonable to watch and wait,” Wein says.

The U.S. Preventive Services Task Force recommendation, which was made public October 11, is not final. It could change after the medical community and the public submit formal comments.

Florida Medicaid


Lawsuit-immunity plan for Medicaid providers costly, report says

A state report says the idea of making doctors who treat Medicaid patients immune to lawsuits would cost the state millions.



TALLAHASSEE — As governor-elect Rick Scott and the Florida Legislature consider giving doctors immunity against lawsuits in return for treating Medicaid patients, a new report warns that such an arrangement could cost taxpayers at least $69 million a year.

State Chief Financial Officer Alex Sink, who lost to Scott in November, commissioned the actuarial report last month after lawmakers indicated they are considering extending the state cap on legal liability, known as sovereign immunity, to Medicaid providers.

The report concludes that if legislators give state immunity to doctors and hospitals, “the state basically takes the place of a doctor who commits a negligent act.” When a patient sues, taxpayers would pick up the tab of any medical malpractice claim up to $300,000. The cost of defending and investigating an estimated 551 claims a year would cost Florida $69 million a year, the report claims.

Florida legislators passed a resolution in November indicating that, during the 2011 regular session, they will enact reforms that “establish a more fair and predictable civil justice system and reduce the disincentive for serving Medicaid participants.” Translation: offer doctors immunity against lawsuits in return for accepting lower payments for treating Florida’s growing Medicaid population.

Sink’s report may be a parting shot at the Republican-controlled Legislature as she prepares to leave office on Jan. 4. But it is likely to be only the first of the salvos fired in the emerging battle over Medicaid reform during the upcoming legislative session. Sink’s campaign was heavily backed by state trial lawyers, while Scott won the support of the liability-averse Florida Chamber of Commerce and the Florida Medical Association.

Sink questions the assumption that doctors will be more willing to accept patients if they are shielded from malpractice claims. “No research has been done that supports that rationale,” the report states, and notes that Florida would be the first state in the country to offer that protection.

But Alan Levine, who headed Scott’s transition team overseeing Medicaid policy, is urging Scott to shield doctors from liability by capping the damages against them, not by giving them sovereign immunity that would cost tax dollars.

“She’s got the right answer, but she’s asking the wrong question,” Levine said of Sink’s report.

The report also raises questions about a policy of having a “two-tiered justice system for medical malpractice claims” by capping recovery for Medicaid patients but not for others.

“I agree that our state Medicaid program needs to be reformed,” Sink wrote in a letter to House Speaker Dean Cannon and Senate President Mike Haridopolos accompanying the report. “However, I do not believe that extending sovereign immunity will convince many doctors to increase the number of Medicaid patients they treat, yet the change could be costly for Floridians.”

Mary Ellen Klas can be reached at meklas@

Read more:

Florida Health Care Policy

Scott’s team urges him to consolidate health agencies into mega department

Gov. Rick Scott should reverse the work of Gov. Lawton Chiles 20 years ago, when he pushed for the separation of the state’s social service agencies, and get back to a large Department of Health and Human Services, Scott’s health care advisory team told him in a 68-page report on Monday.

The goal of the mega-agency would be to better coordinate overlapping functions now handled by the current Departments of Health, Elder Affairs, the Agency for Persons with Disabilities, and the Agency for Health Care Administration as the state attempts to reform the delivery of Medicaid services.

One proposal, submitted Monday Scott’s health care advisory team headed by Alan Levine, calls for sweeping changes in how the state delivers Medicaid and urges a continuation of many of the programs advanced by Levine when he was advising former Gov. Jeb Bush.

Levine, who is the former head of the North Broward Hospital District and formerly served as Health and Hospitals secretary under Louisiana Gov. Bobby Jindal, urged Scott to hire a “quarterback” in his office who could coordinate health policy and management and “be capable of working closely with the legislature.”

Levine predicted that consolidating so many agencies would take “at least a year to plan and implement” but was needed to improve policy coordination.

Among the recommendations:

• Merge the Agency for Persons with Disabilities with the Office of Elder Affairs and have it be a division within a larger health and human services agency
• Keep child welfare programs separate from  a larger health department.
• Continue to fight for repeal of the federal health care reform act because it is “very costly for Florida at the very time we cannot even afford to operate the Medicaid program in its current form.”
• Expand Medicaid reform from the pilot projects in Miami-Dade and Broward counties statewide.
• Adopt Medicaid reform that includes an “organized, coordinated network” of care for the elderly that uses the private sector to give people “services they need” and not necessarily “services they want.” The state would be responsible for providing “proper oversight to ensure needed services are not systemically denied.”

President Barack Obama Receives PSA Test

Despite the recent controversial recommendation by the USPSTF against routine PSA screening, President Barack Obama recently received a PSA test to screen for prostate cancer.

AACU Members and Allies: President Barack Obama recently received a Prostate Specific Antigen test to screen for prostate cancer during his yearly physical. White House physician Dr. Jeffrey C. Kuhlman’s report, which was released October 31st, said the test was performed after the President made an ‘informed patient request.’ The U.S. Preventive Services Task Force recently recommended against PSA-based screening for prostate cancer earlier this month, which they said can do more harm than good. Yet the commander-in-chief felt it was important enough to ask for the test personally. This begs the question: If the President of the United States who has the Country’s best doctors and most current information at his disposal, chooses the PSA test, why shouldn’t all men have the same choice? Obama is fortunate to have the means and knowledge to ask his doctor for a PSA test but if the USPSTF recommends against the test, millions of other men might not be as lucky. The test is not perfect but is currently the easiest and cheapest method of detecting prostate gland abnormalities. We urge you to take action to preserve patients’ choice and save lives. Please be sure to submit comments to the USPSTF as soon as possible before Nov. 8. Links to the USPSTF comments form, as well as pre-written letters to Congress and the media are available at the AACU PSA Test Action Center. Visit the site often to review frequently updated information and resources. Thank You! Click the link below to view this message on the web: You have received this message because you have subscribed to a mailing list of American Association of Clinical Urologists. If you do not wish to receive periodic emails from this source, please click below to unsubscribe.

Dietary Recommendations for the Prevention of Kidney Stones

I have been asked many times by patients what they can do to alter their lifestyle and diet to prevent the formation of kidney stones.  In general, for all stone formers, increasing water intake to generate up to 2 liters of urine per day, decreasing salt and decreasing intake of meats including beef, pork, chicken and fish can help to decrease the risk of stone formation. 

I have attached more formal recommendations from the NIDDK website below:

How does diet affect the risk of developing kidney stones?

Diet is one of several factors that can promote or inhibit kidney stone formation. Other factors include heredity, environment, weight, and fluid intake. The body uses food for energy and tissue repair. After the body uses what it needs, waste products in the bloodstream are carried to the kidneys and excreted as urine. Certain foods create wastes that may form crystals in the urinary tract. In some people, the crystals grow into stones. For people who have had a kidney stone, preventing another will be a priority. In addition to dietary changes, a person may need medicine to prevent kidney stones. The first step in preventing kidney stones is to learn what kind of stones a person’s body typically makes.


What are the types of kidney stones?

  • Calcium oxalate stones are the most common. They tend to form when the urine is acidic, meaning it has a low pH. Some of the oxalate in urine is produced by the body. Calcium and oxalate in the diet play a part but are not the only factors that affect the formation of calcium oxalate stones. Dietary oxalate is an organic molecule found in many vegetables, fruits, and nuts. Calcium from bone may also play a role in kidney stone formation.
  • Calcium phosphate stones are less common. Calcium phosphate stones tend to form when the urine is alkaline, meaning it has a high pH.
  • Uric acid stones are more likely to form when the urine is persistently acidic, which may result from a diet rich in animal proteins and purines-substances found naturally in all food but especially in organ meats, fish, and shellfish.
  • Struvite stones result from infections in the kidney. Preventing struvite stones depends on staying infection free. Diet has not been shown to affect struvite stone formation.
  • Cystine stones result from a rare genetic disorder that causes cystine-an amino acid, one of the building blocks of protein—to leak through the kidneys and into the urine to form crystals.


Why is knowing which type of stone a person has important?

Knowing the chemical makeup of the stone helps the doctor identify why the patient is prone to stone formation. The kind of stone a person’s body makes determines what dietary changes may be needed. For example, limiting oxalate in the diet may help prevent calcium oxalate stones but will do nothing to prevent uric acid stones. Some dietary recommendations may apply to more than one type of stone. Most notably, drinking enough water helps prevent all kinds of kidney stones.


How does a doctor determine the type of kidney stone?

If a person can catch a kidney stone as it passes, the doctor can send the stone to a laboratory for analysis. For stones that are causing symptoms, the doctor may also retrieve a stone surgically or with a scope inserted through the urethra into the bladder or ureter.

The doctor will also order tests to look for unusual levels of chemicals such as calcium, oxalate, magnesium, and sodium in the blood and urine to help design a prevention strategy.


How much fluid should a person drink to prevent stone formation?

The amount of fluid a person needs to drink depends on the weather and the person’s activity level. People who have had a kidney stone should drink enough water and other fluids to produce at least 2 quarts of urine a day. Some doctors have their patients collect urine for 24 hours so the volume can be measured. The doctor can then advise the patient about increasing fluid intake, if necessary. People who work or exercise in hot weather need more fluid to replace the fluid they lose through sweat. Drinking enough water helps keep urine diluted and flushes away materials that might form stones and is the most important thing a person can do to prevent kidney stones.

A person at risk for cystine stones should drink enough water each day to dilute the concentration of cystine that escapes into the urine, which may be difficult. More than a gallon of water may be needed every 24 hours.


What fluids protect against kidney stone formation?

Water is an inexpensive and calorie-free protection against kidney stones.

Some studies suggest citrus drinks like lemonade and orange juice protect against stones because they contain citrate, which stops crystals from growing into stones. But no large-scale trials have been conducted to confirm these findings. While citrus drinks may be helpful in preventing calcium oxalate stones and uric acid stones, they might be harmful for people who form calcium phosphate stones.

Coffee and tea can add to a person’s total fluid intake and have been shown to reduce the risk of stone formation, but they do contain oxalate. Moderate intake of beer and wine may also protect against stone formation.


What fluids should be avoided?

Grapefruit juice and dark colas have been found to increase the risk of stone formation and should be avoided by people who are prone to calcium oxalate stone formation. Although cranberry juice is often promoted as useful for preventing urinary tract infections, it contains oxalate and may be harmful to stone formers.


How does salt in the diet affect kidney stone formation?

Salt is made up of sodium and chloride. The sodium in salt, when excreted by the kidneys, causes more calcium to be excreted into the urine. High concentrations of calcium in the urine combine with oxalate and phosphorus to form stones. Reducing salt intake is preferred to reducing calcium intake.

The U.S. recommended daily allowance (RDA) of sodium is 2,400 milligrams (mg), but Americans’ intake averages 3,300 mg, according to the National Heart, Lung, and Blood Institute. The risk of kidney stones increases with increased daily sodium consumption. Limiting salt to the U.S. RDA goal of 2,400 mg is an important step for people who form calcium oxalate or calcium phosphate stones. People taking medications-such as hydrochlorothiazide, chlorthalidone, or indapamide-to prevent stones still need to limit salt intake.


How can a person limit sodium intake?

Learning the sodium content of foods can help people control their sodium intake. Food labels provide information about sodium and other nutrients. Keeping a sodium diary can help a person limit sodium intake to 2,400 mg. When eating out, people should ask about the sodium content of foods they order.

Some foods have such large amounts of sodium that a single serving provides a major portion of the daily allowance. Foods that contain high levels of sodium include

  • hot dogs
  • canned soups and vegetables
  • processed frozen foods
  • luncheon meats
  • fast food


People who are trying to limit their sodium intake should check labels for ingredients and hidden sodium, such as

  • monosodium glutamate (MSG)
  • sodium bicarbonate, the chemical name for baking soda
  • baking powder, which contains sodium bicarbonate and other chemicals
  • disodium phosphate
  • sodium alginate
  • sodium nitrate or nitrite



How does animal protein in the diet affect kidney stone formation?

Meats and other animal proteins-such as eggs and fish-contain purines, which break down into uric acid in the urine. Foods that are especially rich in purines include organ meats, such as liver. People who form uric acid stones should limit their meat consumption to 6 ounces each day.

Nondairy animal proteins may also increase the risk of calcium stones by increasing the excretion of calcium and reducing the excretion of citrate into the urine. Citrate prevents kidney stones, but the acid in animal protein reduces the citrate in urine.


How does calcium in the diet affect kidney stone formation?

Calcium from food does not increase the risk of calcium oxalate stones. Calcium in the digestive tract binds to oxalate from food and keeps it from entering the blood, and then the urinary tract, where it can form stones. People who form calcium oxalate stones should include 800 mg of calcium in their diet every day, not only for kidney stone prevention but also to maintain bone density. A cup of low-fat milk contains 300 mg of calcium. Other dairy products such as yogurt are also high in calcium. For people who have lactose intolerance and must avoid dairy products, orange juice fortified with calcium or dairy with reduced lactose content may be alternatives. Some studies indicate that calcium supplements increase the risk of calcium oxalate stone formation. Researchers theorize that calcium must be taken at the same time as dietary oxalate to protect against stone formation. Calcium supplements taken with meals may have the same protective effect as dietary calcium.


How does oxalate in the diet affect kidney stone formation?

Some of the oxalate in urine is made by the body. But eating certain foods with high levels of oxalate can increase the amount of oxalate in the urine, where it combines with calcium to form calcium oxalate stones.


How can a person limit oxalate in the urine?

Many foods and beverages contain oxalate, but only a few have been shown to increase the amount of oxalate in urine:

  • spinach
  • rhubarb
  • nuts
  • wheat bran


Avoiding these foods may help reduce the amount of oxalate in the urine. Eating foods containing calcium also reduces oxalate in the urine. Calcium binds oxalate in the digestive tract so it is not excreted into the urine.


How does alcohol affect kidney stone formation?

Although drinking alcohol may promote purine production in the body, studies have not shown more stones in people who drink beer and wine. People should have no more than two drinks-two 12-ounce servings of beer or two 5-ounce servings of wine or two 1.5-ounce servings of hard liquor-a day.


How do supplements affect kidney stone formation?

Supplements containing vitamin C or D may contribute to stone formation. Vitamin C is ascorbate and can be turned into oxalate by the body. Doctors recommend no more than 500 milligrams each day for people who have had kidney stones. Calcium supplements should be taken with meals so the calcium can bind with the oxalate in food. A person who has a tendency to form kidney stones should consult a doctor or dietitian before taking large doses of vitamins or minerals.


How does a person’s weight affect kidney stone formation?

Studies have shown that being overweight increases the risk of uric acid and calcium kidney stones. Scientists don’t know whether losing weight by itself can reduce the risk of kidney stones. Maintaining a healthy weight through healthy food choices and exercise may help reduce the risk of kidney stones.


Can a dietitian help a person prevent kidney stones?

Yes. After a doctor has completed an evaluation and determined the causes of a person’s stones, a dietitian can help a person plan meals that lower the risk of forming stones. People who form stones can ask their doctor or nurse to help them find a dietitian who specializes in kidney stone prevention or renal, or kidney, nutrition.


Questions to Ask the Doctor

  • What kind of kidney stone do I have?
  • How much fluid should I drink every day?
  • How much protein and what type of protein should I eat every day?
  • Am I getting enough calcium in my diet?
  • Can you recommend a dietitian who specializes in kidney stone prevention or renal nutrition?
  • Do I need to take medication to prevent kidney stones?


Points to Remember

  • Diet is one of several factors that can promote or inhibit kidney stone formation.
  • Different kinds of kidney stones require different prevention diets.
  • Drinking water and other fluids is the most important thing a person can do to prevent kidney stones.
  • People who have had a kidney stone should drink enough water and other fluids to make at least 2 quarts of urine each day.
  • Diets high in salt, or sodium, can increase the excretion of calcium into the urine and thus increase the risk of calcium containing kidney stones. Reducing salt intake is preferred to reducing calcium intake.
  • Foods rich in animal proteins-such as meat, eggs, and fish-contain purines and can increase the risk of uric acid stones and calcium stones.
  • Calcium from food can help prevent kidney stone formation and help maintain bone density.
  • Avoiding foods rich in oxalates, such as spinach and rhubarb, may help prevent calcium oxalate stones.
  • After a doctor has completed an evaluation and determined the causes of a person’s stones, a dietitian can help a person plan meals that lower the risk of forming stones.


Hope through Research

The Division of Kidney, Urologic, and Hematologic Diseases of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) funds research on the causes, treatments, and prevention of kidney stones. The NIDDK is part of the National Institutes of Health in Bethesda, MD. NIDDK-sponsored researchers are working to answer the following questions:

  • What dietary factors promote or protect against stone formation?
  • How can doctors predict, or screen, those at risk for getting stones?
  • Do genes play a role in stone formation?
  • What is the natural substance(s) found in urine that blocks stone formation?


Participants in clinical trials can play a more active role in their own health care, gain access to new research treatments before they are widely available, and help others by contributing to medical research. For information about current studies, visit


For More Information

American Urological Association Foundation
1000 Corporate Boulevard
Linthicum, MD 21090
Phone: 1-866-RING-AUA (1-866-746-4282) or 410-689-3700
Internet: click to view disclaimer page click to view disclaimer page

National Kidney Foundation, Inc.
30 East 33rd Street
New York, NY 10016
Phone: 1-800-622-9010 or 212-889-2210
Fax: 212-689-9261
Internet: click to view disclaimer page

Oxalosis and Hyperoxaluria Foundation
201 East 19th Street, Suite 12E
New York, NY 10003
Phone: 1-800-OHF-8699 (1-800-643-8699) or 212-777-0470
Fax: 212-777-0471
Internet: click to view disclaimer page

You may also find additional information about this topic by visiting MedlinePlus at

This publication may contain information about medications. When prepared, this publication included the most current information available. For updates or for questions about any medications, contact the U.S. Food and Drug Administration toll-free at 1-888-INFO-FDA (1-888-463-6332) or visit Consult your doctor for more information.



Publications produced by the Clearinghouse are carefully reviewed by both NIDDK scientists and outside experts. This fact sheet was reviewed by Gary Curhan, M.D., Harvard Medical School, and David Goldfarb, M.D., New York University School of Medicine.


National Kidney and Urologic Diseases Information Clearinghouse

3 Information Way
Bethesda, MD 20892–3580
Phone: 1–800–891–5390
TTY: 1–866–569–1162
Fax: 703–738–4929

The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the National Institutes of Health of the U.S. Department of Health and Human Services. Established in 1987, the Clearinghouse provides information about diseases of the kidneys and urologic system to people with kidney and urologic disorders and to their families, health care professionals, and the public. The NKUDIC answers inquiries, develops and distributes publications, and works closely with professional and patient organizations and Government agencies to coordinate resources about kidney and urologic diseases.

This publication is not copyrighted. The Clearinghouse encourages users of this publication to duplicate and distribute as many copies as desired.

NIH Publication No. 09-6425
May 2009


Page last updated: September 2, 2010