Purpose Almost everyone knows someone who
has had kidney stones. The kidneys filter the blood to remove
excess mineral salts and other soluble (dissolvable) wastes.
The kidneys also produce the urine that dissolves these wastes
and excretes them through the urinary tract. Kidney stones
form when the urine becomes so saturated with a certain
mineral that no more of it can dissolve into the urine (like
trying to dissolve too much sugar in your iced tea). The
undissolved portion of the mineral forms crystals that then
clump together and grow into hard stones. Kidney stones
usually develop in the kidneys. However they can form anywhere
in the urinary tract. This condition is medically known as
urolithiasis or nephrolithiasis.
When kidney stones are
quite tiny, they may pass unnoticed with the urine. Often
however, they grow too large to pass easily through the
urinary tract, and some stones have rough or sharp edges. When
these stones are passing through the urinary tract, it can be
quite painful. In some cases, kidney stones cannot pass on
their own, and treatment with specialized medical equipment or
surgery may be necessary.
For most people, kidney
stones are like dandelions in the lawn; they can be
eliminated, but they'll be back another year. Therefore, a
major part of the treatment for this condition is aimed at
preventing recurrences.
There are various types of
kidney stones. Because treatment for each differs, it is
important for the physician to determine the stone's mineral
content and to identify any medical conditions that may have
contributed to stone formation. Preventive treatment may be
with medications and/or changes in the diet.
About 80% of all kidney
stones are composed of calcium and other minerals, usually a
combination of calcium and oxalate. In some cases dietary
adjustments help to prevent the recurrence of these types of
stones.
Kidney stones occur in men
more than women, and may have a variety of causes including
your diet, your family genes, and other factors.
1.
Increase fluid intake. This is the
most important preventive measure for all patients who develop
kidney stones. It hinders the formation of stones by diluting
the urine. For example, more sugar can be dissolved in a full
glass of iced tea than in a half glass. Patients should drink
enough fluid to produce two quarts or more of urine each day.
As a guideline, drink 8-10 oz of fluid every hour while awake,
and 8-10 oz once during the night if awakened for some reason.
At least 50% of the total fluid intake should be water. In
warmer climates and for physically active people, an even
higher fluid intake is recommend
Another approach to
preventing kidney stones in adults is to eat calcium rich
foods and avoid oxalates. This works in two ways 1) reducing
the amount of oxalate available, and 2) if calcium is present
in the diet with oxalate, then calcium and oxalate bind in the
intestine. This way, less calcium and oxalate enter the blood
so that oxalates are not available to bind with calcium in the
kidney.
2. Moderate Calcium Intake: Unless told otherwise by your physician, it is not necessary
to deprive yourself of calcium; nor should you take it in
excess. Instead, moderate your intake, and you should
be fine. Calcium from food sources is absorbed during
digestion in the intestines. The body uses this mineral for
many important functions. Any excess that has been absorbed is
excreted or passed through the kidneys. The biggest portion of
calcium in the diet comes from milk and foods made from large
amounts of milk, such as cheeses and yogurt. The calcium in
these foods is usually easily absorbed. 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. You should not
use calcium supplements unless you talk to your doctor.
3.
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.
Beans
Grits
String, wax
Instant Coffee
Legume types (including baked beans
canned in tomato sauce)
Leeks
Beets
Nuts
Blackberries
Okra
Carob powder
Peels (lemon & lime)
Celery
Black Raspberries
Chocolate/cocoa other chocolate drink
mixes
Red currants
Dark Leafy greens
Rhubarb
Spinach
Soy products/tofu
Swiss chard
Strawberries
Beet greens
Summer Squash
Endive, escarole
Sweet potatoes
Parsley
Tea
Draft beer
Wheat bran
Fruit cake
Wheat germ
Eggplant
4. Sugar, sodium, and
animal protein: It has been found
that 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. The physician or registered dietitian
can recommend a daily protein intake for individual patients.
5. 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
The Austin Diagnostic Clinic, A
Multi-Specialty Medical Clinic
12221 MoPac Expressway North |
Austin, TX 78758 | 512.901.1111
Serving the communities of Austin, Round Rock, Pflugerville, San
Marcos and
Central Texas since 1952
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