I’m just a cow, doing cow stuff.

We know two facts about kidney stones:

1. Nearly 80% of kidney stones are calcium based, according to the National Institutes of Health (NIH)
2. Milk has a lot of calcium; an 8 ounce glass of milk contains about 300 mg of calcium, according to Harvard University Health Services

So the logic should follow that consumption of more calcium should increase the chances of getting kidney stones, right?

Nope. In fact, it is just the opposite, at least for calcium oxalate stones, the most common stone by far.  It appears that calcium that comes from our food and beverages is actually beneficial, according to a study from the University of Wisconsin.

Our body does three major things with calcium:

1. Stores it in our bones and teeth
2. Uses it to help our muscles move and our nerves to function
3. Gets rid of it (poop or pee)

Oxalate is a chemical that is found in a number of foods, such as spinach, nuts, tea, and chocolate.  When consumed together with calcium, such as that from dairy products, the oxalate binds with excess calcium that is not stored or used in the intestines and passes harmlessly out of the body.

If there is not enough calcium in the intestines, i.e. it’s being absorbed by your body, then the oxalate passes into your kidneys and hooks up with any calcium atoms it can find, forming the crystals that are the starting point for kidney stones.

Mark’s Bottom Line

I don’t drink a lot of milk or eat yogurt, but I eat a lot of cheese.  The problem with most cheeses is that they are high in sodium, which has been found to increase the chances of kidney stones.  Some types of cheese are very dense in calcium as well.  I agree with the experts, in my own experiences, that milk is generally okay. If you enjoy a lot of dairy products, you might want to consider increasing your citrate intake, to aid in the prevention of kidney stones.

The general recommendation from kidney stone experts is to get about 800 mg of calcium through your food, either dairy or otherwise.  I recommend the guide from Harvard University Health Services (see sources below) as a good reference.
References:

• Harvard University Health Services – Calcium Content in Common Foods
• NIH – Calcium and Kidney Stones
• University of Wisconsin – Calcium May Help Prevent Kidney Stones