Calcium kidney stones make up the majority of kidney stones, representing about 80 percent of the total incidence of renal stone disease. Calcium combines with oxalate and phosphate in the intestines and urinary tract to promote the formation of solid, calcium stones. While there is no direct cause of calcium oxalate kidney stones per se, a number of factors can influence calcium oxalate stone formation.
Genetics
According to the National Institutes of Diabetes and Dietary and Kidney Diseases (NIDDK), genetics and family history contribute strongly to kidney stone formation. Calcium oxalate kidney stones form in individuals who have high levels of calcium, oxalate and acid in their urine. The exact reasons for above normal levels of calcium and oxalate are largely unknown but can involve genetic factors that regulate the absorption of calcium and oxalate and promote kidney stone formation.
Diet
Calcium can combine with oxalate during digestion to form calcium oxalate. When calcium combines with oxalate, it is not readily absorbed into the body and stones can form as the kidneys and urinary tract collect high levels of calcium oxalate. According to the Oxalosis and Hyperoxaluria Foundation, a diet rich in oxalate-containing foods can promote stone formation. This includes a lot of dark leafy vegetables such as spinach, chard and beets as well as chocolate, black tea and soy bean crackers. Interestingly, diets rich in calcium have little effect on stone formation and may actually protect against kidney stone risk, according to the NIDDK. The use of calcium supplements or vitamin D or vitamin C supplements may however promote kidney stones and should be avoided by those at risk for kidney stones. Regular use of calcium carbonate antacids can also increase stone formation.
Acid in the Urine
Calcium oxalate and calcium phosphate precipitate from the urine more readily to form a stone when urine becomes too acidic. A diet rich in protein and meats can increase urine acidity and help stones to form. Insulin resistance also increases urine acidity and the risk for stone formation, putting diabetics and obese individuals at risk for calcium stones.
Inadequate Fluids
Calcium, oxalate, and acids also concentrate in the urine of individuals with inadequate fluid intake levels. For this reason, it is recommended that those at risk for calcium kidney stones drink at least 12 glasses of water per day. This will help to flush excess calcium and oxalate from the kidneys and also help to decrease urine acidity.
