Diet for Kidney

Stone Prevention
National Kidney and Urologic Diseases Information Clearinghouse

How does diet affect the risk stones are more common. Calcium
oxalate stone formation may be caused
of developing kidney stones? by high calcium and high oxalate
Kidney stones can form when substances excretion. Calcium phosphate stones
in the urine—such as calcium, oxalate, and are caused by the combination of
phosphorus—become highly concentrated. high urine calcium and alkaline urine,
The body uses food for energy and tissue meaning the urine has a high pH.
repair. After the body uses what it needs,
waste products in the bloodstream are • Uric acid stones form when the
carried to the kidneys and excreted as urine. urine is persistently acidic. A diet
Diet is one of several factors that can rich in purines—substances found in
promote or inhibit kidney stone formation. animal protein such as meats, fish,
Certain foods may promote stone formation and shellfish—may increase uric
in people who are susceptible, but scientists acid in urine. If uric acid becomes
do not believe that eating any specific food concentrated in the urine, it can settle
causes stones to form in people who are and form a stone by itself or along with
not susceptible. Other factors that affect calcium.
kidney stone formation include genes, • Struvite stones result from kidney
environment, body weight, and fluid intake. infections. Eliminating infected stones
from the urinary tract and staying
More information about kidney stones
infection-free can prevent more
can be found in the National Kidney
struvite stones.
and Urologic Diseases Information
Clearinghouse fact sheets Kidney Stones • Cystine stones result from a genetic
in Adults and Kidney Stones in Children at disorder that causes cystine to leak
www.kidney.niddk.nih.gov. through the kidneys and into the
urine, forming crystals that tend to
What are the types of kidney accumulate into stones.

stones?
Four major types of kidney stones can form:
• Calcium stones are the most common
type of kidney stone and occur in two
major forms: calcium oxalate and
calcium phosphate. Calcium oxalate
Why is knowing which type
of kidney stone a person has Dietary Changes to Help
important? Prevent Kidney Stones
The first step in preventing kidney stones People can help prevent kidney stones
is to understand what is causing the stones by making changes in fluid intake and,
to form. This information helps the health depending on the type of kidney stone,
care provider suggest diet changes to changes in consumption of sodium,
prevent future kidney stones. For example, animal protein, calcium, and oxalate.
limiting oxalate in the diet may help prevent Drinking enough fluids each day is the
calcium oxalate stones but will do nothing best way to help prevent most types of
to prevent uric acid stones. Some dietary kidney stones. Health care providers
recommendations may apply to more than recommend that a person drink 2 to
one type of stone. Most notably, drinking 3 liters of fluid a day. People with
enough fluids helps prevent all kinds of cystine stones may need to drink even
kidney stones by keeping urine diluted and more. Though water is best, other
flushing away materials that might form fluids may also help prevent kidney
stones. stones, such as citrus drinks.
Recommendations based on the
How does a health care specific type of kidney stone include the
provider determine the type following:
of kidney stone?
Calcium Oxalate Stones
If a person can catch a kidney stone as it
passes, it can be sent to a lab for analysis. • reducing sodium
Stones that are causing symptoms can be • reducing animal protein, such as
retrieved surgically or with a scope inserted meat, eggs, and fish
through the urethra into the bladder or
• getting enough calcium from food
ureter, then sent to a lab for analysis.
or taking calcium supplements with
Blood and urine can also be tested for food
unusual levels of chemicals such as calcium, • avoiding foods high in oxalate,
oxalate, and sodium to help determine what such as spinach, rhubarb, nuts, and
type of kidney stone a person may have had. wheat bran
Calcium Phosphate Stones
• reducing sodium
• reducing animal protein
• getting enough calcium from food
or taking calcium supplements with
food
Uric Acid Stones
• limiting animal protein

2 Diet for Kidney Stone Prevention

How much fluid should a The U.S. recommended dietary allowance
(RDA) of sodium is 2,300 milligrams (mg),
person drink to prevent but Americans’ intake averages 3,400 mg,
kidney stone formation? according to the U.S. Department of
People who have had a kidney stone should Agriculture.1 The risk of kidney stones
drink enough water and other fluids to increases with increased daily sodium
produce at least 2 liters of urine a day. consumption. People who form calcium
People who have had cystine stones may oxalate or calcium phosphate stones should
need to drink even more. The amount of limit their intake to the U.S. RDA level,
fluid each person needs to drink depends even if they take medications to prevent
on the weather and the person’s activity kidney stones.
level—people who work or exercise in hot
weather need more fluid to replace the fluid How can a person limit
they lose through sweat. A 24-hour urine
collection may be used to determine the sodium intake?
volume of urine produced during a day. If Learning the sodium content of foods can
the volume of urine produced is too low, help people control their sodium intake.
the person can be advised to increase fluid Food labels provide information about
intake. Drinking enough fluid is the most sodium and other nutrients. Keeping
important thing a person can do to prevent a sodium diary can help a person limit
kidney stones. sodium intake to 2,300 mg. When eating
out, people should ask about the sodium
Some studies suggest citrus drinks like content of the foods they order.
lemonade and orange juice protect against
kidney stones because they contain citrate, Some foods have such large amounts of
which stops crystals from growing into sodium that a single serving provides a
stones. major portion of the RDA. Foods that
contain high levels of sodium include
How does sodium in the • hot dogs
diet affect kidney stone • canned soups and vegetables
formation? • processed frozen foods
Sodium, often from salt, causes the kidneys
• luncheon meats
to excrete more calcium into the urine.
High concentrations of calcium in the urine • fast food
combine with oxalate and phosphorus to
form stones. Reducing sodium intake is
preferred to reducing calcium intake.

1U.S. Department of Agriculture and U.S. Department

of Health and Human Services. Dietary Guidelines

for Americans, 2010. 7th ed. Washington, D.C.: U.S.
Government Printing Office; December 2010.

3 Diet for Kidney Stone Prevention

People who are trying to limit their sodium How does calcium in the
intake should check labels for ingredients
and hidden sodium, such as
diet affect kidney stone
formation?
• monosodium glutamate, or MSG
Calcium from food does not increase the
• sodium bicarbonate, the chemical
risk of calcium oxalate stones. Calcium in
name for baking soda
the digestive tract binds to oxalate from
• baking powder, which contains sodium food and keeps it from entering the blood,
bicarbonate and other chemicals and then the urinary tract, where it can
form stones. People who form calcium
• disodium phosphate oxalate stones should include 800 mg of
• sodium alginate calcium in their diet every day, not only
for kidney stone prevention but also to
• sodium nitrate or nitrite maintain bone density. A cup of low-fat
milk contains 300 mg of calcium. Other
How does animal protein in dairy products such as yogurt are also high
the diet affect kidney stone in calcium. For people who have lactose
intolerance and must avoid dairy products,
formation? orange juice fortified with calcium or
Meats and other animal protein—such as dairy with reduced lactose content may be
eggs and fish—contain purines, which break alternatives. Calcium supplements may
down into uric acid in the urine. Foods increase the risk of calcium oxalate stones if
especially rich in purines include organ they are not taken with food.
meats, such as liver. People who form
uric acid stones should limit their meat
consumption to 6 ounces each day. How does oxalate in the
diet affect kidney stone
Animal protein may also raise the risk of
calcium stones by increasing the excretion formation?
of calcium and reducing the excretion of Some of the oxalate in urine is made by
citrate into the urine. Citrate prevents the body. However, eating certain foods
kidney stones, but the acid in animal with high levels of oxalate can increase
protein reduces the citrate in urine. the amount of oxalate in the urine, where
it combines with calcium to form calcium
oxalate stones. Foods that have been
shown to increase the amount of oxalate in
urine include
• spinach
• rhubarb
• nuts
• wheat bran
Avoiding these foods may help reduce the
amount of oxalate in the urine.

4 Diet for Kidney Stone Prevention

What diet plan should a Points to Remember
person follow to prevent • Kidney stones can form when
future kidney stones? substances in the urine—such as
calcium, oxalate, and phosphorus—
A dietitian can help a person plan meals
become highly concentrated. Diet is
that lower the risk of forming stones based
one of several factors that can promote
on the type of stone the person formed in
or inhibit kidney stone formation.
the past. A person with a history of kidney
stones may want to talk to a dietitian who • Four major types of kidney stones can
specializes in kidney stone prevention or form: calcium stones, uric acid stones,
nutrition for people with kidney problems. struvite stones, and cystine stones.

A dietitian can also help overweight people • Drinking enough fluid is the most

plan meals to help them lose weight. Studies important thing a person can do to

have shown that being overweight increases prevent kidney stones.

the risk of kidney stones, particularly • People who have had a kidney stone
uric acid stones. Diets that are low in should drink enough water and other
carbohydrates have been shown to further fluids to make at least 2 liters of urine
increase the risk of uric acid stones and a day.
should be avoided.
• Sodium, often from salt, causes the
Studies have shown the Dietary Approaches kidneys to excrete more calcium into
to Stop Hypertension (DASH) diet can the urine. High concentrations of
reduce the risk of kidney stones. The calcium in the urine combine with
DASH diet is high in fruits and vegetables, oxalate and phosphorus to form
moderate in low-fat dairy products, and stones. Reducing sodium intake is
low in animal protein. More information preferred to reducing calcium intake.
about the DASH diet can be found on the
• Meats and other animal protein—such
National Heart, Lung, and Blood Institute’s
as eggs and fish—contain purines,
website at www.nhlbi.nih.gov/health/
which break down into uric acid in the
health-topics/topics/dash.
urine.
• 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.
• A dietitian can help a person plan
meals that lower the risk of forming
stones based on the type of stone the
person formed in the past.

5 Diet for Kidney Stone Prevention

Hope through Research Tamsulosin for Urolithiasis in the
Emergency Department, funded under NIH
The National Institute of Diabetes and
clinical trial number NCT00382265, studies
Digestive and Kidney Diseases (NIDDK)
the effectiveness and safety of tamsulosin in
funds research on the causes, treatments,
treatment of kidney stones. Other areas of
and prevention of kidney stones. The
focus include reduction in time to pain-free
International Registry for Hereditary
recovery, decrease in narcotic medication
Kidney Stone Diseases, funded under
for pain, less need for follow-up, decrease
National Institutes of Health (NIH) clinical
in the need for surgery, and cost savings.
trial number NCT00588562, collects
medical information from a large number Clinical trials are research studies involving
of patients with kidney stones to create a people. Clinical trials look at safe and
registry that will help researchers compare effective new ways to prevent, detect, or
similarities and differences in patients and treat disease. Researchers also use clinical
their symptoms. trials to look at other aspects of care, such
as improving the quality of life for people
The Study of the Biological and Physical
with chronic illnesses. To learn more about
Manifestations of Spontaneous Uric Acid
clinical trials, why they matter, and how to
Kidney Stone Disease, funded under NIH
participate, visit the NIH Clinical Research
clinical trial number NCT00904046, aims
Trials and You website at www.nih.gov/
to determine how much fat accumulates
health/clinicaltrials. For information about
within cells and how it affects the kidneys
current studies, visit www.ClinicalTrials.gov.
by correlating kidney fat content with urine
test results. A second aim is to evaluate the
effect of the medication thiazolidinedione
on excess fatty acid accumulation in kidney
tissue and its correlation with uric acid
stone formation.

6 Diet for Kidney Stone Prevention

For More Information Acknowledgments
National Kidney Foundation Publications produced by the
30 East 33rd Street Clearinghouse are carefully reviewed by
New York, NY 10016 both NIDDK scientists and outside experts.
Phone: 1–800–622–9010 or 212–889–2210 The original version of this fact sheet was
Fax: 212–689–9261 reviewed by Gary Curhan, M.D., Harvard
Internet: www.kidney.org Medical School, and David Goldfarb, M.D.,
New York University School of Medicine.
Oxalosis and Hyperoxaluria Foundation
201 East 19th Street, Suite 12E
New York, NY 10003
You may also find additional information about this
Phone: 1–800–OHF–8699 topic by visiting MedlinePlus at www.medlineplus.gov.
(1–800–643–8699) or 212–777–0470 This publication may contain information about
Fax: 212–777–0471 medications. When prepared, this publication
Email: kimh@ohf.org included the most current information available.
For updates or for questions about any medications,
Internet: www.ohf.org contact the U.S. Food and Drug Administration toll-
free at 1–888–INFO–FDA (1–888–463–6332) or visit
Urology Care Foundation www.fda.gov. Consult your health care provider for
1000 Corporate Boulevard more information.
Linthicum, MD 21090
Phone: 1–800–828–7866 or 410–689–3700
Fax: 410–689–3998
Email: info@urologycarefoundation.org
Internet: www.UrologyHealth.org

7 Diet for Kidney Stone Prevention

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NIH Publication No.13–6425

February 2013

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