Dr. Dean

Does Coffee Cause Kidney Stones?

Posting Date: 10/23/2000

Mike: I have a history of kidney stones and I also drink about a quart of coffee a day.

My friend's doctor says that too much coffee can cause kidney stones. Do you buy that?

Also, do you recommend I have the stones analyzed by a lab?

Dr. Dean: Kidney stones should absolutely be analyzed by a lab and health insurance plans should pay for such tests. An analysis to determine the composition of stones is as essential to a health evaluation as is knowing your blood pressure and your cholesterol level.

Kidney stones come in a few basic types; calcium in combination with oxalate, phosphate or carbonate is the most common. Uric acid stones are also somewhat common. Depending on which type of stones you have, you should avoid certain types of food.

As far as coffee is concerned, some studies find that coffee may thin the bones. If coffee does thin the bones, emphasis on "if," that process of thinning may be dumping extra calcium into the urine. Extra calcium in the urine seems to relate to some of the calcium-based kidney stones. So on one hand, avoiding coffee is recommended.

However, people with kidney stones are told to drink plenty of fluids to flush out urine. Coffee, being a diuretic, promotes urination and may in that way be helpful in fighting kidney stones.

I'm a coffee drinker and I won't let anyone slam coffee unnecessarily. But I have to tell you, Mike, that a quart of coffee a day is a lot of coffee. For the sake of your other body parts, you might want to modify that habit.