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Citric Acid &
Kidney Stones
What are kidney stones?
Kidney stones are crystals usually formed by
the precipitation of the mineral salt calcium oxalate from the
urine. The resulting hard, round stones (calculi) may cause severe pain,
especially as they pass down the urinary tract. Large stones may need to
be surgically removed or broken down using ultrasound therapy. Below are
kidney stone crystals, captured by colored scanning electron micrograph
(SEM).
What is citric acid? How can it help?
Citric acid is an organic acid and a natural
component of many fruits and fruit juices. It is not a vitamin or
mineral and is not required in the diet. However, citric acid, not to be
confused with ascorbic acid (vitamin C), is beneficial for people with
kidney stones. It
inhibits stone formation
and
breaks up small stones that are beginning to form.
Citric acid is protective; the more citric acid in your urine, the more
protected you are against forming new kidney stones.
Citrate,
used in calcium citrate supplements and in some medications (such as
potassium citrate), is closely related to citric acid and also has stone
prevention benefits. These medications may be prescribed to
alkalinize
your urine.
How does citric acid protect against kidney stones?
Citric acid makes urine less favorable for the formation of stones. In
its natural form, such as from citrus fruits, citric acid does not
alkalinize the urine as citrate (from medication) does. Rather, it
prevents small stones from becoming “problem stones” by coating them and
preventing other material from attaching and building onto the stones.
What are the
best food sources of citric acid?
Citric acid is most prevalent in citrus fruits and juices. Of these
fruits, lemons and limes have the most citric acid. While oranges,
grapefruits, and berries also contain appreciable amounts,
lemons and limes
will most significantly contribute to the citric acid content of your
urine. Pharmacological doses of citric acid, prescribed as potassium
citrate, are effective in the treatment of stones. However, treatment
may be costly and require as many as 12 tablets daily.
A half-cup (4 ounces) of pure lemon juice per day or 32 ounces of
prepared lemonade provide about the same amount of citric acid as does
pharmacological therapy.
Keep reading for tips to increase your citric acid intake and minimize
your risk for developing kidney stones. In addition to increasing your
citric acid consumption, drinking adequate fluids (at least ten 8-ounce
glasses per day) – more in hot weather or when physical activity
promotes heavy perspiration – may be the most powerful way to decrease
your risk of developing stones.
Easy Tips to Increase
Your Citric Acid Intake:
Eat
5 or more fruits and vegetables daily.
As lemons and limes provide the most citric acid per gram, these
tips focus on them. Remember, though, that increasing your intake
of all fruits and vegetables – especially the citrus variety –
will add to your citric acid intake and provide other health
benefits as well. For example, the potassium, magnesium, and
phytic acid (phytate) contained in fruits and vegetables protect
you against forming new stones. Other phytochemicals in plant
foods prevent cancer and other chronic diseases.
* Here’s a tip
to get more juice from lemons – roll them on a hard surface while
pressing down with your palm. Or, heat them for about 30 seconds
in the microwave before squeezing.
-
Squeeze fresh lemon (or
reconstituted lemon juice) into ice cube trays before freezing.
Directions: Fill trays almost full with water. Then, squeeze half
a lemon or more over the tray, and freeze. Use these cubes for
sprucing up plain tap water and other beverages. If you like the
taste of lime, use lime instead of, or in addition to, lemons.
Remember to drink at least 10 glasses of fluid every day to
keep your urine dilute enough to prevent stones.
-
Squeeze fresh
lemon or lime juice directly into your soda, fruit juice, tea, or
water.
-
Use lemon
juice. Dilute 2 ozs. lemon juice with 6 ozs. water and drink
twice a day – once in the morning and once in the evening – to
reach the goal of 4 ozs. lemon juice per day.
-
Drink
lemonade every day. Depending on your urinary citrate
concentration, 16-32 ozs. daily may be recommended, distributed
throughout the day. To make homemade lemonade, squeeze a ˝ cup (4
ounces) of fresh lemon juice into a pitcher of cold water; bottled
lemon juice may also be used. Add sugar or sugar substitute, if
desired. Make it by the glass for a single serving. Or, use
commercially available lemonade products and mixes. We strongly
recommend low-calorie lemonades and lemonade mixes (such as
Minute Maid Light, Tropicana Light, or Crystal Light).
These are high in citric acid but have little sugar and few
calories. Of the commercially-available lemonade products, those
that are ready-to-consume have more citric acid than those that
come as a powder.
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Make a lemon
or lime spritzer. Here’s how: Pour 2 cups fresh lemon or lime
juice (from about 9 medium size lemons or limes; or use lemon or
lime juice concentrate) into a large pitcher. Add 1 cup Splenda®,
a no-calorie sweetener made from sugar. When sugar is fully
dissolved, add 1 liter chilled club soda, thin lemon & lime
slices, and a few ice cubes. Stir and chill thoroughly before
serving.
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Use fresh
lemon on lettuce or spinach salads. You may find yourself
using
less of those high-fat salad dressings!
-
Use freshly
squeezed lemon or lime on fruit salads. Besides adding a zesty
taste, the acid in the juice will prevent cut fruits, such as
apples, from browning with exposure to air. You’ll have
better-looking and healthier fruit salads.
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Use lemon or
lime juice on fish and in marinades for any type of meat.
When looking for marinades and other recipes, try the ones that
call for lemon or lime juice, and incorporate them into your menus
at home.
-
Read the
label. Choose products that are high in citric acid. Some
lemon-lime sodas, for example, are relatively high in citric acid.
If you drink soda, consider switching to one that’s high in citric
acid.
Other nutritional changes that must be
considered:
In addition to limiting the intake of meat, sugar, salt, and fruit
juice (except lemon juice), a basic kidney-stone prevention program
should include:
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An increase of dietary fiber
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10,000 units of vitamin A
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300 mg of magnesium citrate
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100 mg of vitamin B6 each day
-
Vitamin C concerns : Studies have dispelled the myth that higher
amounts of vitamin C promote calcium oxalate kidney stone
formation.. But if you take three or more grams of vitamin C each
day, have your doctor measure your urinary oxalate.
Are citric acid and ascorbic acid the same
thing?
Citric acid and ascorbic acid are not the same thing. Indeed, ascorbic
acid is the more versatile and essential of the two acids.
Ascorbic acid,
or
vitamin C,
has a chemical make-up of C6H8O6. While it is found in citrus fruits,
billygoat plums, rose hips, blackcurrants, guavas, kiwi fruits, broccoli,
and Brussels sprouts are much better sources. Most animals can also
produce it themselves, although most fish, some birds, all guinea pigs,
and some primates — and man — cannot, and so must get it from other
sources.
In cooking, besides keeping cut fruits and vegetables from turning brown,
ascorbic acid promotes the growth of yeast, and so is also often added as
an enhancer to bread dough. In commercial food processing it is used as an
antioxidant preservative.
Citric acid
has one more oxygen atom than ascorbic acid; its formula is C6H8O7. It
occurs naturally in citrus fruits and some other fruits and vegetables. It
can also be synthetically produced from sugar.
Citric acid is used commercially to enhance the tartness in fruit-flavored
candy and in soft drinks. It is also added to some ice creams to keep fat
globules from coagulating. Some bakers use it in sourdough bread to
produce an especially assertive tang.
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