Could your diet be contributing to kidney stones?

Q. I have developed kidney stones. Is there anything that I might be eating or drinking that could have caused them? I drink two to three cups of mint tea daily — could that be the problem?

A. The types of food you eat and the amount of fluid you drink can sometimes contribute to the formation of kidney stones. Certainly, you can help prevent recurrent kidney stones by paying attention to your fluid and food intake.

Fill yourself with fluids

First and foremost, be sure you drink plenty of fluids every day and avoid dehydration. Kidney stones form when certain minerals concentrate in the urine and form hard crystals. By drinking plenty of fluid, you can decrease the concentration of these minerals. Drink 8 to 12 cups (64 to 96 ounces) a day.

There aren't any particular fluids that you need to avoid. But moderation, as always, is best. Alcohol and caffeine have a diuretic effect, causing the kidneys to make more urine. This is helpful for preventing kidney stones. But if you are drinking too much alcohol or caffeine and not enough water or other liquids, you can dehydrate.

Dietary tips

The most common type of kidney stone is the calcium oxalate stone. About 80% of all kidney stones are made of calcium oxalate. The name might make you think you should eat a low-calcium diet to avoid getting them, but you should actually do the opposite.

The problem is oxalate. Most people who develop calcium oxalate stones absorb too much oxalate. The extra oxalate is absorbed by the intestines and passed into the bloodstream. The body uses what it needs, and the extra oxalate is excreted in the urine. In the urine, the higher concentration of oxalate can combine with calcium to cause kidney stones.

Many of the foods we eat, including some very healthy foods, contain oxalate. So it is difficult to go on an oxalate-restricted diet. What can you do? This is where eating a high-calcium diet comes in. Calcium binds to the oxalate in your intestine. This way less oxalate can get absorbed into your bloodstream, and less will need to pass into your urine.

Some good sources of dietary calcium include low-fat or fat-free dairy products such as milk, yogurt, cottage cheese, and cheese. Other good sources of calcium include calcium-fortified orange juice, calcium-fortified soy milk, tofu, broccoli, sardines, collard greens, almonds, and black beans.

Higher protein intake, especially from animal protein, increases the likelihood of kidney stones. High-protein diets are acidic and reduce the amount of natural stone inhibitors in the urine. In addition, high-protein diets tend to contain more oxalate.

Tea and coffee

Tea and coffee in moderation are not a problem. In fact, some studies suggest that drinking moderate amounts of tea and coffee can actually decrease the risk of kidney stones. Tea and coffee do contain some oxalate, but the amount of water in these drinks more than compensates.

The two to three cups of mint tea you're drinking a day (as well as other herbal teas) should not cause a problem, as long as you are drinking additional amounts of other fluids. Black tea is the one tea that you might avoid, as it has much higher amounts of oxalate.

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