Kidney Stones? Lay Off the Iced Tea

Bad news for iced-tea lovers who also happen to be kidney-stone prone. The refreshing beverage, which I favor because it's tasty even without sweetener, contains high concentrations of oxalate. Turns out oxalate's a key culprit in creating kidney stones.

And if you've ever passed one of those, you know it's worth doing just about anything to avoid them.

The irony is that folks who get kidney stones -- about 5 percent of the U.S. population, according to the National Institutes of Health, though that number's thought to be on the rise -- are supposed to drink lots of liquids to help prevent stones from forming. Just not iced tea.

Kidney stones occur when crystals of calcium and either oxalate or phosphate separate from the urine and bond together; urine contains chemicals that usually keep stones from forming, but those chemicals don't always succeed.

John Milner, a urologist at Loyola University Chicago Stritch School of Medicine, says his patients describe passing a kidney stone -- even a tiny one -- as the most painful experience they've endured. And "if you have one," Milner says, "your chance of having another within five years is 50-50."

Excess salt consumption and obesity are both tied to kidney stone formation, Milner says. Besides tea (and, yes, hot tea's as bad as iced) other high-oxalate foods include spinach, chocolate, nuts and rhubarb. (Say goodbye to that other summertime treat, strawberry-rhubarb pie.)

So what should you sip during these hot summer days? Milner suggests lemonade (made from real lemons, not a powdered mix). "The citrate in the lemons is actually a preventative agent for kidney stones," he says. To cut calories, he says, go ahead and use an artificial sweetener, none of which have been linked to kidney stones. But, he cautions, don't confuse citrate with citric acid, or Vitamin C, and start popping supplements. "Vitamin C gets metabolized to oxalate" and can encourage kidney stones to form if you ingest too much.

Milner recommends another warm-weather treat that can help ward off kidney stones. Contrary to what was once believed, calcium doesn't stimulate stone formation, but instead can inhibit their development. So, Milner suggests, to avoid stones and build your bones -- help yourself to some ice cream!