Since about 70 % of all
kidney stones are made up by
calcium oxalate, avoiding fruit and vegetables that
contain a high amount of oxalate might be part of
any strategy to avoid the build up of further
stones. It doesn't mean however, that you have to
avoid them altogether, as you will see later on.
What exactly is oxalate? It is a substance that
occurs naturally in plants, animals and the human
body. Chemically speaking it belongs to the organic
acids, the exact formula being C2O42−. There are two
sources of oxalate for the human body. First of all
it is produced within human cells, the body converts
certain substances (like Vitamin C for example) to
oxalate. The second source are oxalate rich foods,
like certain fruit and vegetable. Recent research
has shown, that the oxalate intake has a relatively
small impact, other factors, like intake of water,
protein and calcium also play and important role.
Rather than strict diets doctors tend to recommend a
diet reduced in oxalate, with "as little oxalate as
can be tolerated" without compromising too much
quality of day to day life.
So if your doctor told you to avoid high oxalate
food, here is a small list of some of the groceries
that you should use with moderation: rhubarb,
buckwheat, black pepper, parsley, poppy seed,
eggplant, green beans, amaranth, spinach, chard,
beets, cacao, chocolate (sad, but true), some nuts
like almonds and soy products.
What about fruit? First some fruit containing a
lot of oxalate, that should better be avoided:
Kiwis, black- and blueberries, star fruit, the peel
of citrus fruit, grapes, gooseberries, dried figs,
raspberries, tangerines and red currants. You see,
the list is not too long, there is quite a lot left
to get your five a day!
Here a list of fruit low in oxalate: peeled
apples, avocado, canned cranberries, green seedless
grapes, lemon or lime juice, mangoes melons,
cantaloupe, honeydew, watermelon, nectarines, papaya
and raisins.
Fruit that contains a medium level of oxalate:
apples with their peel, apricots, black currants,
cherries, dried cranberries, grapefruit, grapes,
oranges, peaches, pears, plums and prunes.
Whenever you eat something and get this funny
furry feeling in your mouth (think of rhubarb or raw
blackthorn fruit) there is a good chance it has to
do with the oxalate in the fruit.
Following a diet low in oxalate is one stone in
the mosaic that can help you prevent the development
of new kidney stones. You should see your doctor
though before going on a special diet in order to
determine if your kidney stones are actually caused
by too much oxalate in the urine. He also will tell
you what to do about your protein and calcium
intake, which are two other factors of significance.
Eating more fruit with a low oxalate content might
help you in your quest to avoid kidney stones, but
they are just one part of the puzzle!
