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Kidney Stones
Kidney Stone Diet
Purpose
 The kidneys
filter the blood to remove excess mineral salts and other soluble
(dissolvable) wastes. They also produce the urine that dissolves
these wastes and excretes them through the urinary tract. Stones
form when the urine becomes so saturated with a certain mineral that no
more of it can dissolve into the urine. The undissolved portion of the mineral forms
crystals that clump together and grow hard. Usually develop in the kidneys,
but can form anywhere in
the urinary tract. Medically known as urolithiasis or
nephrolithiasis.
Small stones may pass unnoticed with the
urine. Often though, they grow too large and have rough or sharp edges. When these
stones are passing through the urinary tract, it can be quite painful.
In some cases, stones cannot pass on their own, and treatment
may be necessary. Prevention is important.
Summary:- Usually kidney stones are
calcium, oxalate and phosphate.
Food to Avoid
- A
doctor may recommend to not eat foods rich in oxalate.
Oxalate-Rich Foods
- Spinach, peanuts, chocolate and
sweet
potatoes.
Medium-Oxalate Foods
- Grits, grapes,
green
peppers and strawberries have a medium amount of oxalate.
Eat in small amounts.
Prevention
- Plenty of water,
orange
juice.
Causes of Kidney Stones
More common in times of prosperity. Men are affected than women.
Usually 95% crystalline, while the rest is organic
material. 80-85% are calcium
stones (usually calcium oxalate), 5-10% are uric
acid, 5-10% are "infection stones" (struvite and carbonate
apatite), and 1% are rare varieties, e.g. cystine stones.
Not explained by nutrition alone.
However, diet plays a major role in calcium and uric acid stones,
triggering the formation of stones if a person has a predisposition
(kidney design).
Studies have shown that
-
meat protein
leads to a marked increase in kidney stones.
-
The main risk factors for
calcium stones are a low volume of urine,
- increased excretion of oxalic
acid and calcium (less critical), and a deficiency of citrate, which
inhibits crystallization in the urine.
-
Overly acidic urine is the main
risk factor for the formation of uric acid stones.
Fluids - the most important element
-Drink enough fluid to produce urine of at least 2 litres a day.
-More
on days of profuse sweating or major physical exercise
-fluid
intake is distributed as equally as possible over the course of 24 hours
-Almost
all liquids are suitable, but bicarbonate and calcium-rich mineral
water as well as fruit juices are particularly beneficial.
-Formation of stones is promoted by large quantities of black
tea or iced tea (high oxalate content), cola (very acidic) and beer
("liquid binges" lead to an increase in oxalic acid and uric acid
excretion).
Vegetables - nuts -fruits
-Vegetables and fruits increase the urinary excretion of the
stone-inhibiting citrate.
-Foods with a high oxalate
content (spinach, rhubarb, beetroot, chard and nuts) kept to
minimum
-Combine
these high oxalate foods with foods providing a
plentiful supply of calcium (e.g. spinach with a cheese gratin), this
prevents the absorption of large quantities of oxalate
Meat, poultry, fish
-Excessive intake of protein from meat and fish increases the risk of
stone - the urine is over-acidified and the excretion of oxalate,
calcium and uric acid increases, while the excretion of citrate - which
helps inhibit stone formation - is decreased.
Milk and dairy products
-Contrary to earlier views, restriction of calcium is no longer
recommended.
Salt
-Sodium in common salt can increase the risk of stone formation,
probably by increasing the urinary excretion of calcium. On the other
hand, a drastic reduction of salt leads to a decrease in urinary volume.
A slightly reduced salt intake (to about 8 g per day) is recommended.
Sweets
-Excessive consumption of foods rich in sugar increases the urinary
excretion of calcium and thus possibly also the risk of kidney stone.
Probably more important, however, is the fact that chocolate, pralines
and products containing cocoa have high oxalate content.
-Eat sweets in moderation - exercise restraint especially with
chocolate, pralines and chocolate cakes.
Prevention of Kidney Stones - Dietary recommendations
-Balanced and varied diet
-normal
physical activities
How to eat if you have kidney stones:
Fats and oils:
-Use 2 teaspoonfuls (10 g) of high-quality vegetable oil (e.g. sunflower
oil, thistle oil, corn oil, olive oil, rapeseed oil) per day, unheated,
e.g. for salad dressings.
-Use not more than 2 teaspoonfuls (10 g) of cooking fat or oil per day
(e.g. peanut oil, olive oil) for the preparation of meals.
-Do not eat more than 2 teaspoonfuls (10 g) of spreading butter or
margarine per day on bread.
-Do not eat more than one high-fat meal per day, such as deep-fried or
breaded food, cheese dishes, fried potato, sausage, cream sauce, puff
pastry, cakes, chocolate.
Cereal products and potatoes:
Eat at least 3 portions of carbohydrate-rich foods per day, such as
bread (100% whole grain), potatoes (limit if you desire low carb diet),
rice (limit if you desire low carb diet), cereal (limit if you desire
low carb diet), or pasta (limit if you desire low carb diet), preferably
wholegrein products. Small portions.
Fruit:
Eat 3 portions of fruit a day (1 portion = 1 apple, 1 banana, 3
plums or a dish of berries), ideally raw.
Vegetables:
Eat 3 - 4 portions of vegetable per day, at least one of them raw, e.g.
as a dip or a mixed salad (1 portion = 100 g raw or 150 - 200 g cooked
vegetable).
Exercise restraint, however, with spinach, chard and rhubarb
(preferably eat these vegetables together with dairy products, e.g.
spinach with cheese gratin).
How to drink if you have kidney stones:
Liquids:
Drink at least 10 glasses /day, unsweetened and alcohol-free
liquids. Black tea or ice tea, cocoa drunk in small quantities.
Alcohol:
Limit: 2 glasses of wine or beer a day. 1 day a week without
alcohol.
- 8 glasses of unsweetened liquids daily
- Use less salt
- Limit meat
- Limit oxalate-rich foods
- High-fibre foods
Additional Nutrition Facts
-Diets for managing calcium kidney stones have adequate nutrients for
most healthy adults.
-Calcium
supplements are generally not recommended, unless approved by a
physician.
| Special Considerations |
- Increase fluid intake: Hinders the formation of stones by
diluting the urine.
- Calcium: Any excess that
has been absorbed is passed through the kidneys.
The biggest portion of calcium in the diet comes foods made from large amounts of milk, such as cheeses
and yogurt. The calcium in these foods is usually easily
absorbed. Other foods, such as dark green leafy vegetables,
contain significant amounts of calcium. However, they also
contain other substances which prevent the body from readily
absorbing the calcium. So, the amount of available calcium
in green leafy vegetables is less than in milk. Certain
antacids and over-the-counter medications also contain
calcium that may or may not be in a form the body can absorb
Usually the body does not absorb more calcium than is
needed. However, certain conditions can cause too much
calcium to be absorbed, or too much to be passed into the
kidneys. Too much calcium in the urine is medically known as
hypercalciuria. Only in certain cases of hypercalciuria may
calcium stones be prevented controlling the amount of
calcium in the diet.
| Food Sources of Calcium |
Gruyere Cheese, 1 oz.
Mozzarella Cheese, 1 oz
Cheddar Cheese, 1 oz.
Yogurt, 1/2 cup
Macaroni & Cheese, 1/2 cup
7" Homemade Waffle, 1
Vanilla Ice Cream, 1 cup
Ice Milk, 1 cup
American Cheese, 1 oz
Ricotta Cheese, 1/4 cup |
287
207
204
200
200
179
176
176
174
167 |
Instant Oatmeal, 3/4 cup
2% Cottage Cheese, 1 cup
Broccoli, 1 stalk
Pizza, 1 slice
Milk, 1/2 cup
Buttermilk, 1/2 cup
Baked Custard, 1/2 cup
Pudding, 1/2 cup
Blackstrap Molasses, 1 T
Instant Nonfat Dry Milk, 2 T |
163
155
150
150
150
150
149
146
137
105 |
If the physician has recommended a calcium controlled diet,
follow their instructions in all cases.
Patients on a calcium-controlled diet should consult the
physician before taking any over-the-counter medication or
vitamin supplement. For examples of foods containing calcium
that is easily absorbed, see the table Food Sources of
Calcium.
- Oxalic acid or oxalate is found mostly
in foods from plants. Calcium combines with oxalate in the
intestines. This reduces calcium's ability to be absorbed.
Sometimes oxalate or calcium oxalate stones form because
there is not enough calcium in the intestines. Then, too
much oxalate goes to the kidneys to be excreted. The medical
term for too much oxalate in the urine is hyperoxaluria. In
certain cases of oxalate or calcium oxalate stones, the
physician may recommend reducing oxalate intake along with a
slight increase in calcium. It is recommended that these
patients have no more than 50 mg of oxalate per day in the
diet. To do this, foods with high or moderate amounts of
oxalate should be reduced or eliminated from the diet.
Although there are many foods that contain large amounts of
oxalate, eight foods have been shown to be most at fault for
raising urine oxalate levels. They are rhubarb, spinach,
strawberries, chocolate, wheat bran, nuts, beets, and tea.
For more information about the oxalate content of foods, see
the table, Foods High in Oxalate on page 6.
- Sugar, sodium, and animal protein: Too much of these may also aggravate the
development of calcium or calcium oxalate stones. Some
sugars occur naturally in foods and that is not a concern.
However, people who get kidney stones may benefit from
avoiding packaged foods with large amounts of added sugars,
and from reducing sugars added in food preparation and at
the table.
Reducing sodium in the diet appears to reduce the amount of
calcium excreted in the urine. Consequently, people who
develop stones containing calcium may benefit from keeping
sodium intake between 2300 to 3500 mg a day.
A diet high in animal protein affects certain minerals in
the urine that may promote the formation of kidney stones.
Therefore, people who tend to develop kidney stones should
avoid eating more protein than the body needs each day.
- Insoluble fiber: Fiber is the
indigestible part of plants. There are two types of fiber:
soluble (dissolves in water) and insoluble. Both provide
important functions in the body, but it is insoluble fiber
(found in wheat, rye, barley, and rice) that may help to
reduce calcium in the urine. It combines with calcium in the
intestines, so the calcium is excreted with the stool
instead of through the kidneys. Insoluble fiber also speeds
up movement of substances through the intestine, so there
will be less time for calcium to be absorbed.
- Vitamin C: When vitamin C is used by
the body, oxalate is produced. Therefore, if the physician
has recommended reducing oxalate in the diet, taking vitamin
C supplements may not be a good idea. It should be discussed
with the physician.
|
Foods High in Oxalate
(More than 10 mg per 1/2 cup serving) |
Beans (string, wax)
Legume types (including baked beans
canned in tomato sauce)
Beets
Blackberries
Carob powder
Celery
Chocolate/cocoa, other chocolate drink mixes
Dark leafy greens
Spinach
Swiss chard
Beet greens
Endive, escarole
Parsley
Draft beer
Fruit cake
Eggplant |
Gooseberries
Grits (white corn)
Instant coffee (more than 8 oz/d)
Leeks
Nuts, nut butter
Okra
Peel: lemon, lime, orange
Raspberries (black)
Red currants
Rhubarb
Soy products (tofu)
Spinach
Strawberries
Summer squash
Sweet potatoes
Tea
Wheat bran
Wheat germ
|
Sample Menu For Kidney Stones
Calcium or Calcium Oxalate Stones |
| Breakfast |
Lunch |
Dinner |
grapefruit juice 1 cup
cereal 3/4 cup
skim milk 1 cup
scrambled eggs 1
white toast 2 slices
margarine 2 tsp
coffee 1 cup
water 1 cup |
white meat chicken 2 oz
wheat bread 2 slices
iceberg lettuce 1 cup
oil/vinegar dressing 1 Tbsp
cantaloupe 1 cup
lemonade 1 cup
sugar cookie 1
water 1 cup |
baked haddock 3 oz
white rice 1/2 cup
peas 1/2 cup
margarine 2 tsp
dinner roll 1
apple 1
animal crackers 16
water 1 cup |
| This Sample Diet Provides the Following |
| Calories |
1805 |
Fat |
51 gm |
| Protein |
81 gm |
Sodium |
1821 mg |
| Carbohydrates |
261 gm |
Potassium |
692 gm |
What Is It?
Kidney stones are abnormal, hard, chemical deposits that form inside
the kidneys. This condition also is called nephrolithiasis or
urolithiasis. Kidney stones are often as small as grains of sand and
pass out of the body in urine without causing discomfort. The deposits
can be the size of a pea, a marble or even larger. Some of these larger
stones are too big to be flushed from the kidney. Others manage to
travel into the narrow tube between the kidney and bladder (ureter),
where they become trapped. Trapped kidney stones can cause many
different symptoms, including extreme pain, blocked urine flow and
bleeding from the walls of the urinary tract.
Kidney stones are a very common problem, affecting 10% of people in
the United States. There are several different types of stones, and a
variety of reasons why stones form. Doctors have grouped kidney stones
into four different families, based on their chemical composition:
- Calcium oxalate stones — These stones account for more
than 75% of all kidney stones. They are more common in men than in
women, and they are more common in adults than in children. In 50%
of people with calcium stones, the stones form because of an
increased level of calcium in the urine, which probably is inherited
(genetic). In other people, calcium oxalate stones are caused by
another condition such as extra parathyroid hormone, high uric acid
levels (as in people who have gout), bowel disease, surgery for
obesity, or kidney problems.
- Struvite stones — These stones are made of magnesium and
ammonia (a waste product), and are related to urinary tract infections
caused by certain bacteria. Struvite stones used to account for 10% to
15% of all kidney stones, but they are less common now that urinary
tract infections are better recognized and treated. Struvite stones are
more common in women than in men, and they develop frequently in people
who have long-term bladder catheters.
- Uric acid stones — These stones account for 5% to 8% of
all kidney stones, and are more common in men than in women. Uric
acid stones form because of an abnormally high concentration of uric
acid in the urine. They often occur in people who have gout, a
disorder in which uric acid builds up in the blood and joints.
- Cystine stones — These rare stones account for less than 1%
of kidney stones. They are composed of the amino acid cystine, which is
a building block of proteins, and they are caused by an inherited
(genetic) defect.
Diagnosis
Your doctor will ask you about your symptoms and about any change in
the color of your urine. He or she will ask about your family history of
kidney stones, and whether you have had gout.
If you are in extreme pain, your doctor can use X-rays, computed
tomography (CT) scans or ultrasound to look for a kidney stone and see
if it is trapped. If you are able to collect a stone that you passed
from your urine, your doctor will send the stone to a lab for
analysis.
If you do not have any symptoms and you find a small kidney stone in
your urine, strain out the stone and save it for your doctor.
Expected Duration
It can take hours, days or weeks for a stone to
pass. The smaller the stone, the more likely it is to pass on
its own. The larger the stone, the greater the risk that it will remain
trapped in the ureter, significantly obstructing the flow of urine and
eventually causing infection.
Prevention
In general, you can help to prevent kidney stones by drinking plenty
of fluids and avoiding dehydration.
You can prevent calcium oxalate stones by eating low-fat dairy
products and other calcium-rich foods. Taking calcium supplements,
however, can increase the risk of stone formation. Calcium in your diet
binds oxalate inside the intestines to decrease the amount of oxalate
that gets into the blood, so less spills in the urine. People who
excrete too much oxalate into their urine should avoid eating foods high
in oxalate, including beets, spinach, chard and rhubarb. Tea, coffee,
cola, chocolate and nuts also contain oxalate, but these can be used in
moderation. Eating too much salt and meat can cause more kidney stones
to form.
Treatment
A trapped stone eventually flushes out on its own, especially if you drink plenty of fluids. With
a doctor's supervision, it is likely that you can remain at home, taking
pain medicine as needed until the stone dislodges and flushes away. If
the stone is too large to pass on its own, if your pain is severe, or if
you have infection or significant bleeding, it may be necessary for you
to have your stone removed or broken into fragments that can pass more
easily. Doctors have several options:
- Extracorporeal lithotripsy — Shock waves applied
externally break kidney stones into smaller fragments, which are
then swept away in the urine stream.
- Percutaneous ultrasonic lithotripsy — A narrow tubelike
instrument is passed through a small incision in the back to the kidney,
where ultrasound breaks up the kidney stones. The stone fragments are
then removed.
- Laser lithotripsy — A laser breaks up stones in the
ureter. The stones then pass on their own.
- Ureteroscopy — A very small telescope is inserted into the
ureter and guided to the bladder. The stone is then either fragmented or
removed.
It is rare that surgery is required.
Once a kidney stone has been removed, you can sometimes prevent new
stones from forming with medications or changes in diet. For example,
thiazide diuretic medications may be prescribed for some people with
calcium stones, while some people with uric acid stones may be treated
with allopurinol (Aloprim, Zyloprim).
When To Call A Professional
Call your doctor whenever you have:
- Severe pain in your back or side, with or without nausea and
vomiting
- Unusually frequent urination or a persistent urge to urinate
- A burning and discomfort when urinating
- Urine that is colored pink or tinged with blood
Because trapped kidney stones can lead to a urinary tract infection,
call your doctor if you have fever and chills, or if your urine becomes
cloudy or foul smelling.
Prognosis
Up to half of people who pass a
kidney stone will never pass a second.
Additional Info
National Institute of Diabetes and Digestive and Kidney Disorders
Office of Communications and Public Liaison Building 31, Room 9A04
Center Drive, MSC 2560 Bethesda, MD 20892-2560 Phone: (301) 496-3583
Fax: (301) 496-7422
http://www.niddk.nih.gov/
American Foundation for Urologic Disease 1000 Corporate Blvd.,
Suite 410 Linthicum, MD 21090 Phone: (410) 689-3990 Toll-Free: (800)
828-7866 Fax: (410) 689-3998
http://www.afud.org/
National Kidney Foundation 30 East 33rd St. New York, NY 10016
Phone: (212) 889-2210 Toll-Free: (800) 622-9010 Fax: (212) 689-9261
http://www.kidney.org/
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