While calcium oxalate is a natural product in many foods, people with hyperoxaluria, oxalosis or a history of calcium oxalate kidney stones should know that many common foods are high in oxalates. Calcium oxalate stones are the most common type of kidney stone, formed when calcium crystallizes with oxalates. Diets high in oxalates can increase kidney stone formation. Controlling intake of high oxalate foods may help prevent calcium oxalate kidney stones.
Vegetables that are moderate or high in oxalates include endives, asparagus, eggplant, brussels sprouts, cucumbers, celery and beets. Also, most leafy green vegetables such as chard or beet greens are quite high in oxalate. As an example, raw spinach contains about 750 mg of oxalates per 100 g serving.
High oxalate fruits include rhubarb, figs, blueberries, blackberries, raspberries, kiwifruit, grapes and limes. In addition, citrus fruit peel such as lemon peel is high in oxalates. Because oxalates are resistant to cooking, products derived from citrus peel, such as orange marmalade, maintain their oxalate content. Rhubarb contains about 700 mg of oxalates per 100 g serving.
Nuts and Seeds
Most nuts and many types of seeds are high in oxalates. This includes tree nuts such as almonds, walnuts, cashews and pecans, which contain about 200 mg of oxalates per 100 g serving. Sunflower and sesame seeds are examples of seeds that are known for their oxalate content; sesame seeds have about 100 mg per 100 g serving.
Peanuts, pinto beans, black beans and soybeans are high in oxalates. So are products derived from these foods, such as peanut butter, refried pinto beans, and tofu, which is a fermented product of soybeans. Soy-based veggie burgers contain about 800 mg of oxalates per 100 g serving, while tofu contains about 200 mg of oxalates per 100 g serving, and peanuts contain about 180 mg of oxalates per 100 g serving.
Starches and Carbohydrates
A variety of foods in this group are high in oxalates. Grains such as wheat--the germ and the bran--are high in oxalates, as are rye, millet and oats. Starchy foods that are high in calcium oxalate include cornstarch, corn, potatoes and sweet potatoes. Sweet potatoes have about 60 mg of oxalates per 100 g serving.
Beer, tea and coffee are beverages that are high in oxalates. Because soy, chocolate and tomatoes are high in oxalates, soy milk, hot chocolate and tomato juice are all high in oxalates, too. A cafe mocha made with soy milk has about 100 mg of oxalates per 100 g serving.