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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!

By Jennifer LaRue Huget  |  August 15, 2008; 7:00 AM ET
Categories:  General Health  
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That's a great column - I never knew any of that - thanks!

Posted by: Bob M | August 15, 2008 8:25 AM | Report abuse

Does this apply to all teas? I'm wondering if I should cut back on my drinking white tea, which I drink hot, each day. Thanks

Posted by: Hot tea also | August 15, 2008 11:04 AM | Report abuse

The statement "don't confuse citrate with citric acid, or Vitamin C" confuses ascorbic acid (vitamin C) with citric acid.
Citrates are 'salts' of citric acid.

Posted by: Larry | August 15, 2008 11:16 AM | Report abuse

Ms. Huget,

Citrate and citric acid are the same thing, though citrate generally refers to the conjugate base form of citric acid. It's Vitamin C that shouldn't be confused with citrate/citric acid.

Posted by: TEL1 | August 15, 2008 11:25 AM | Report abuse

isn't Vitamin C ascorbic acid?? It just gets confused with citric since they are in fruits together.

Posted by: amwhite1 | August 15, 2008 12:10 PM | Report abuse

After I had a calcium-oxalate stone, I was told I can't have black tea but can have green tea.

Posted by: Elsie | August 15, 2008 2:36 PM | Report abuse

ETA: The urologist also said that 95% of kidney stone prevention is not diet but drinking enough water.

Posted by: Anonymous | August 15, 2008 2:38 PM | Report abuse

Calcium binds oxalate in the gastrointestinal tract so it never gets to the kidneys. Water is the key, though, as the article says. A glass of water an hour after meals is a good idea.

Posted by: J Conrad | August 15, 2008 4:08 PM | Report abuse

are kidney stones genetic?

Posted by: gg | August 15, 2008 4:21 PM | Report abuse

Why do we bother living at all! Seems like everything is a contradiction. Tea is great for its antioxidants but now lay off because it causes Kidney stones. After working out, watching my carbs, watching my sugars, Cholesterol, blood pressure and Hypertension, you're not going to take my beloved Green and Peach teas! Man up and pass the stones!

Posted by: Eleventh Earl of Mar | August 15, 2008 4:53 PM | Report abuse

I had an episode with 3 kidney stones about a month ago and 2 a year and a half prior. Percocet does wonders but I also contracted a kidney infection. I was drinking alot of OJ, water and raspberry tea. I still drink OJ but just not as much and now completely cut out raspberry tea. Is it ok to drink green tea?

Posted by: Jeremy | August 15, 2008 4:56 PM | Report abuse

My daughter has had several kidney stones and her doctor told her to cut out dairy but Milner says the opposite. Are there different causes?

Posted by: Gramma | August 15, 2008 5:11 PM | Report abuse

I got kidney stones on my 31st b-day, they didnt and still dont know why ... I still have them. Mine have never gone away, I am 34 now. I drink lots of water and when it gets too bad I use pain meds. Ya cant just say CUT OUT TEA and you will be fine .. PFF Listen guys your DOC is the only one that can tell you what kind of stones and why .. I have cut out certain foods to stop them and it didnt do anything. SO dont believe all that you read!!

Posted by: Angela | August 15, 2008 5:42 PM | Report abuse

There are more than one kind of kidney stone, with different causes. As for the oxalate potential of tea, that can be neutralized by putting milk in your tea, (Hot or iced-- no lemon, please) as the oxalic acid will bind to the calcium in the milk and pass through your system, instead of binding to calcium in the blood.

Nobody really know as much as they think they do about why stones form. For each person geneticallly prone to oxalate kidney stones, there are millions more who never will get one.

Spinach actually has far more oxalate than tea (and there is a case of an Indian man who died from eating too much spinach one day), same goes for rhubarb which can be toxic if wrong parts are used.

However, the same rule about calcium and also eating in moderation applies to spinach and rhubarb. I love rhubarb-strawberry sauce on my ice cream.

Next time you do a story, ask the experts "is this the only way X is formed, from oxalic acid." Half of the trick of scientific journalism is ASKING the right questions, otherwise you wind up with a misleading article that can promote food hysteria.

Posted by: Wilbrod | August 15, 2008 6:10 PM | Report abuse

i had my first stone. it was surgically removed. cystomy. im was shock to here that ice tea will cause this. glad to know. going to drink more lemon water. thank you.

Posted by: nelson m | August 15, 2008 6:40 PM | Report abuse

Skim milk can cut some calories (compared to whole, 2%, 1.5%, and/or 0.5%) but still has calcium. Of course it will have some calcium but fewer calories than ice cream!

Posted by: E. Salinas | August 15, 2008 7:00 PM | Report abuse

Thanks for the info.... I usually have iced tea and peanuts to keep me awake during work, I work night shifts....So what can you recommend in place for iced tea-peanut comdo?

Posted by: Mae | August 15, 2008 8:11 PM | Report abuse

Only BLACK tea, folks--you can drink all the other kinds, just as long as the base is not black. There are all kinds of other teas you can substitute black tea for and they also have antioxidant properties and are quite tasty.

And on the "man up" suggestion to go ahead and pass a stone? Clearly you've never had to pass one so you'd be wise not to comment on this. Not only is passing a stone incredibly painful ...if the stone is large enough it can also cause damage to the ureters (stones are jagged not smooth) which can lead to other health problems.

You can take vitamin supplements as long as you TAKE THEM WITH FOOD. This way the vitamins and minerals can be properly absorbed instead of just passing through your system and overloading your kidneys. The most important preventative measure is to increase your water intake.

Posted by: A.M. | August 15, 2008 8:26 PM | Report abuse

The DSIB recommends a COMBINATION of Magnesium citrate and Potassium citrate for
oxalate kidney stone prevention.


for more information.

Posted by: Leslie K | August 16, 2008 3:16 PM | Report abuse

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