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Why is Iced Tea and not Hot Tea bad for kidney stones?

By July 27, 2008 - 12:20pm
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I just read the EmpowHer News article that says ice tea is the worst thing that someone is who is prone to kidney stones can drink (which is my husband), due to the oxalates in the iced tea.

Why is it specifically ice tea and not hot tea? Aren't they made from the same thing? Is it actually more about the quantity of tea? (it is easier to drink a large quantity of iced tea than hot tea). Is there any such thing as tea without oxalates? As the article says, we drink tea because we thought it was healthier than soda, and we get tired of drinking water.

(you can read article here: https://www.empowher.com/news/kidneys-and-urinary-system/2008/07/25/iced...)

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EmpowHER Guest

I think it is a mater of quantity, let me explain:
Iced tea, since it is drank in large quantities, usually due to the hot environmental temperature, introduce a greater amount of oxalate than the hot variety (It's impossible to drink 1,5 liter of hot tea in the summer!)
Furthermore, being iced tea a processed food, the crystallized sugar in it contributes to stones formation.

September 11, 2013 - 6:11am
EmpowHER Guest

In answer to the question, "why would you be more likely to get kidney stones from ice tea?", I believe it has something to do with the fact that most people put milk in hot tea. The kidney stones that form from oxalate are made of oxalate and calcium. My understanding is that if the oxalate can combine with the calcium in the digestive system, it will not combine in the urine. Wouldn't the same also be true for calcium (in the milk) mixing with the oxalate (in the tea) inside the cup? I'm not a doctor so I'm not offering a medical opinion here. But it makes sense to me that this would be the difference between hot tea and ice tea.

March 25, 2012 - 10:14am

Yeah, in fact, drinking tea increased your chance of kidney stones. Otherwise, I think you should avoid caffeine and carbonated beverages which can make urine. Similarly, high sugar intake is associated with increased risk of kidney stones, so you can cut hundreds of calories and prevent future kidney stones by staying away from sugary drinks and foods. Keeping this step, you will pass your stones through your urine more effective.
(Link removed by EmpowHER moderator.)

February 19, 2010 - 8:58pm
(reply to mrsmaria7)

mrsmaria, no no no. The evidence on tea is mixed. The large study showed a modest decrease in kidney stones upon tea drinking. Nonetheless, tea, specifically black tea, is quite high in oxalates, which are responsible for most kidney stones. One suggestion is to be sure that the tea is either Green, Oolong or herbal, thus decreasing the oxalate content. Another is to go British, and add an ounce or so of cow's milk to each cup of (hot) tea. The calcium in the milk prevents the intestinal uptake of the oxalates. finally, in general, it's beneficial to keep fluid intake high. Water is recommended. So long as the kidneys have plenty of water, it's less likely that calcium oxalates will precipitate.

May 19, 2010 - 2:21pm
EmpowHER Guest

In other words the science does not support the hypothesis that drinking tea increased your chance of kidney stones. In fact the opposite is true.

April 24, 2009 - 9:19am

Interesting question. We have forwarded your question to a tea expert who may be able to supply us with an answer on this one.

We also found a little bit of information that addresses why tea may be an issue in terms of kidney stones, but does not distinguish between hot and iced teas.

"Two large prospective studies found that the risk of developing symptomatic kidney stones decreased by 8% in women (61) and 14% in men (62) for each 8-ounce (235 mL) mug of tea consumed daily. A study in rats concluded that the antioxidants in green tea may be involved in inhibiting calcium oxalate precipitation and thus kidney stone formation (63). The implications of these findings for individuals with a previous history of calcium oxalate stone formation are unclear. High fluid intake, including tea intake, is generally considered the most effective and economical means of preventing kidney stones (64). However, tea consumption has been found to increase urinary oxalate levels in healthy individuals (65), and some experts continue to advise people with a history of calcium oxalate stones to limit tea consumption."


Details to come.

July 28, 2008 - 10:14am
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