Iced Tea Linked to Kidney Stones
Saturday, August 11, 2012
Iced tea contains high concentrations of oxalate, one of the key chemicals that lead to the formation of kidney stones, a common disorder of the urinary tract that affects about 10 percent of the population in the United States. "For people who have a tendency to form the most common type of kidney stones, iced tea is one of the worst things to drink," said Dr. John Milner, assistant professor, Department of Urology, Loyola University Chicago Stritch School of Medicine.
What causes kidney stones
The most common cause of kidney stones is not drinking enough fluids. And during the summer, people can become dehydrated from sweating. Dehydration, combined with increased iced tea consumption, raises the risk of kidney stones, especially in people already at risk.
"People are told that in the summertime they should drink more fluids," Milner said. "A lot of people choose to drink more iced tea, because it is low in calories and tastes better than water. However, in terms of kidney stones, they might be doing themselves a disservice."
The issue with iced tea
Though hot tea also contains oxalate, it's hard to drink enough to cause kidney stones, Milner said. About 85 percent of tea consumed in the United States is iced, according to the Tea Association of the USA. Men are four times more likely to develop kidney stones than women, and the risk rises dramatically after age 40. Postmenopausal women with low estrogen levels and women who have had their ovaries removed also are at increased risk.
Kidney stones are small crystals that form from minerals and salt normally found in the urine in the kidneys or ureters, the small tubes that drain urine from the kidney to the bladder. Kidney stones usually are so small they are harmlessly expelled from the body. But stones sometimes grow large enough to become lodged in the ureters.
Local expert: Gyan Pareek, MD
How much iced tea would be too much?
This is a difficult question to answer. For example, the exact amount of oxalate in an 8-oz. glass of iced tea is not known. What is known is that excessive intake (more than two glasses daily) will lead to increased oxalate in the urine. This in turn may lead to an increased chance of getting a kidney stone.
Men are four times more likely to develop kidney stones that women. Who else is at risk?
That number is a little high. Normally, men are two times more likely than women to form a kidney stone. That spread may be decreasing. Others at risk include obese patients, persons on certain medicines like topomax (used for headaches), patients who have had gastric bypass surgery as well as patients whose direct relatives may have had kidney stones. Others include patients who have conditions where calcium deposits may form in the kidney known as "medullary sponge kidney."
If we need to watch our iced tea intake, what's a better way to hydrate?
Water is the best way to hydrate. If an alternative source is sought, one should consider adding lemons to their diet. Lemons have citrate in them and can help prevent kidney stones from clumping together. Lemons can be taken in a lot of different forms from fresh lemons squeezed, lemon juice or even as lemonade.
Are there other sources of oxalates that we should keep an eye on?
Yes, normally green leafy vegetables, nuts, cashews, rhubarb, chocolates, and green tea are some common sources of oxalate. I tell my patients "everything in moderation." Extreme intake of any one food is not good.
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