Oxalates are compounds produced by plants to protect them from insects and diseases. In small amounts, oxalates help the human body manage calcium. But in large amounts, they can crystallise, causing problems such as kidney stones, gout and arthritis. Since oxalates are naturally occurring in many foods, careful attention to diet is necessary to prevent or treat these problems.
Many fruits have high oxalate contents and should be avoided. Among them are berries (such as blackberries and raspberries), currants, figs, kiwi, oranges, papayas and starfruit. While lemon and lime juices do not contain high levels of oxalates, their peels do, and so baked goods, beverages and other products that might contain citrus zest or oil as well as juice.
Fruits high in oxalate can be replaced by fruits low in oxalates, such as apples, apricots, avocados, grapes, melon, peaches, pineapple and plums. Try grapes frozen for a snack, or make an apple salad with coconut (replacing high-oxalate walnuts) and yoghurt dressing.
Beets, broccoli, carrots, celery, okra, olives, potatoes, spinach and other dark leafy greens and tomatoes are all high in oxalates. This may seem very limiting at first, but there are other vegetables at your disposal. Red bell pepper, cauliflower, cucumber, green peas, cabbage, acorn squash, onions, pumpkin, asparagus and zucchini are all low in oxalates.
In addition, the oxalate content of some vegetables changes depending on how they are prepared. Tomatoes have a high oxalate content when cooked and canned, but lower oxalate content when fresh. Cauliflower's oxalate content can be lowered even more by boiling it. Broccoli has a high oxalate content when steamed, but is fine to eat fresh. Carrots should not be steamed or eaten raw, rather boiled, for a lower oxalate content.
Meats and Protein
Most meats and dairy products contain very low concentrations of oxalates. Beans and nuts, on the other hand, have high concentrations of oxalates (with the exception of coconut, black-eyed peas and yellow split peas). Green split peas, mung beans, chick peas, and tofu (made from soybeans) have lower concentrations of oxalates than most legumes. They still should be eliminated in the early stages of a low-oxalate diet, but they can be reintroduced slowly.
Corn, barley, rice, wheat, rye and millet all contain low amounts of oxalates. The concentration of oxalates in different types and brands of pasta varies. Wheat should be avoided in the early stages of a low-oxalate diet, but different types of wheat product can be introduced slowly, depending on the body's reaction.