The vast majority of kidney stones are made of calcium oxalate.
“Oxalate comes from some foods we eat, and the body also produces oxalate,” explains Gary Curhan, a nephrologist and a professor of medicine at Harvard Medical School and professor of epidemiology at the Harvard School of Public Health. “Spinach has a huge amount. We advise people who have formed calcium oxalate stones not to eat spinach.”
Potatoes are another major source of calcium oxalate in the American diet. “Wheat bran and some nuts are also high in oxalate, though the amount differs by type,” explains Curhan. “But nuts and bran have health benefits, so I tell my patients to eat them in moderation unless they have a very high urine oxalate.”
Here is a list of some higher oxalate foods that you may want to avoid if you are prone to calcium oxalate kidney stones: