Re: Does calcium supplements cause kidney stones?

Will taking calcium supplements cause an increase in kidney stones?

Not necessarily.

First thing to keep in mind is that there are a number of different types of kidney stones.  Uric acid, calcium oxalate, phosphate, struvite, etc.

There is some concern that the taking of calcium supplements can increase the risk of calcium oxalate stones if taken with oxalate sources such as coffee, tea, chocolate, rhubarb, etc.  This is not the case though.  When calcium and oxalic acid are taken together dietarily the two combine to form an insoluble salt that is not absorbed.  Therefore it cannot reach the kidneys.

There are a few ways though that calcium can increase the risk of stones. One is if the person takes large amounts of highly alkaline calcium oxide (hydroxide) or calcium carbonate.  These can alkalinize the urine too much, which can lead to the formation of calcium or phosphorus based stones.  The ingestion of large amounts of calcium ascorbate could increase the risk of calcium oxalate stones as the excess ascorbic acid is broken down in to oxalic acid binding with the calcium.