Oxalates are naturally-occurring chemicals in nature. The chemicals are found in the human body, as well as in animals, but are most common in fruits and vegetables. As a general rule, the leaves of a fruit and vegetable will contain more oxalates than the stems and shoots of the plant. Some rare medical conditions require low oxalate diets, and some health professionals believe that oxalates contribute the formation of kidney stones, so you may need to know which foods contain the most oxalates.


Fruits

Darker-colored fruits and vegetables produce more oxalates than lighter-colored plants, as a general rule. In general, a food is considered to have a high oxalate level if there are more than 10 milligrams of oxalates per serving of the food.

High oxalate fruits include many berries, including blackberries, blueberries, raspberries and strawberries. Red or purple grapes also tend to contain a high level of oxalates. Plums, currants, kiwis and tangerines also top the list for high-oxalate foods.

According to the University of Pittsburgh Medical Center, you will also find high levels of oxalate in the peels of many fruits, including oranges, lemons and limes. Remember, also, that juices made from high-oxalate fruits will have high oxalate levels.


Vegetables

There are a large number of green vegetables that contain high oxalate levels. These include spinach, parsley, green pepper, leeks, olives and celery. Non-green vegetables can contain a large number of oxalates as well; some of these include carrots, beets, beans (baked, dried and kidney beans), summer squash and sweet potatoes.


Other Foods

Black tea often contains high amounts of oxalates. This is one of the more controversial high-oxalate foods. Some doctors advise patients to avoid consuming large amounts of tea because they say it contributes to forming kidney stones, while others recommend tea as a preventive for kidney stones because of its diuretic qualities. Other dark drinks, such as hot chocolate, coffee and dark or robust beers, can include high doses of oxalate.

Wheat grains, including multi-grain bread, can have high oxalate levels. Other starch products, such as pretzels, rye or wheat bread and fruit cake can also contribute to high oxalate levels. Similarly, some soy products, such as soybeans and tofu, also fall into this category.

Pay attention to your intake of condiments as well. The University of Pittsburgh Medical Center advises that more than 1 tsp. of black pepper per day, as well as servings of marmalade and soy sauce, can result in high oxalate intake.

Interestingly enough, no meats appear on the lists of high oxalate foods. In fact, meats such as bacon, beef, pork and poultry appear on the list of low-oxalate foods from the University of Pittsburgh Medical Center.