- Calcium oxalate formation typically begins with the presence of excess amounts of calcium in the bloodstream, according to the Urology Channel. The kidneys remove this calcium from the blood, and a buildup of this mineral in the kidneys can cause it to combine with oxalate, a substance produced by the liver and found in certain foods.
- The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC) lists foods with high amounts of oxalate that include beets, spinach, rhubarb, wheat germ, peanuts, okra, sweet potatoes and chocolate.
- The Mayo Clinic and the NKUDIC list additional sources of oxalate or calcium concentration that include certain metabolic disorders, high vitamin D intake, intestinal bypass surgery and creation of an intentional opening between an organ and the skin's surface (ostomy surgery).
- The NKUDIC notes that food sources do not seem to raise levels of kidney stone formation unless an individual is otherwise susceptible to kidney stones.
- Calcium may also combine with phosphate to form calcium phosphate kidney stones, notes the Mayo Clinic.