If urine becomes excessively acidic, normally liquid waste products from the liver may solidify in the kidneys to form “stones” or “calculi”. Such phenomena are relatively rare and usually occur in people with an inherited abnormality in body chemistry.
Because vitamin C is thought of automatically as ascorbic acid by many individuals – including physicians – it is assumed that by taking large quantities of ascorbic acid one will acidify his urine and cause kidney stones to form. Such reasoning overlooks the fact that vitamin C in ascorbic acid form undergoes chemical modification before reaching the kidneys and subsequently does little to alter the acid levels of urine.
If you are concerned – possibly because of a family history of kidney disease – use non-acidifying calcium or potassium ascorbate as your source for C.