Iced Tea Not Best Summer Drink for Kidneys

Iced tea can contribute to kidney stones
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When you think of summer drinks, one of the most popular is iced tea, and lots of it. If you are prone to develop kidney stones, however, iced tea may not be the best beverage for you to enjoy this summer, according to a urologist from Loyola University Chicago Stritch School of Medicine, and here's why.

Iced tea can raise the risk of kidney stones

Much has been researched and written about the health benefits of tea, be it black, oolong, green, or white, although each has its own special qualities. For example, green tea has a high concentration of catechins, especially EGCG, which have demonstrated anticancer qualities and protection in the lungs of smokers while white tea is believed to possess the most anticancer properties of all the teas.

Black and oolong teas are made from fermented tea leaves, and they offer some other benefits. Studies have shown that black tea may reduce the risk of stroke, for example, while oolong has been associated with a reduction in cholesterol. All the teas have caffeine and theanine, which can enhance mental alertness.

But all of these teas also contains oxalate, a chemical that can lead to the formation of kidney stones. Although both hot and iced tea provide oxalate, people are much less likely to drink a great deal of hot tea, or at least enough to increase the risk of developing kidney stones.

However, individuals find it easy to drink lots of iced tea during the summer months, which could be bad news if they are among the estimated 10 percent of the US population who are susceptible to getting kidney stones. In fact, according to Dr. John Milner, assistant professor, Department of Urology at Loyola, "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."

More about kidney stones
Are you at risk for developing kidney stones? Risk factors for kidney stones include

  • Not drinking enough fluids (dehydration)
  • Family history
  • Age 40 years and older
  • Being male: men are 4 times more likely to develop kidney stones than are women
  • Eating a certain diet, especially one high in protein, sodium, and sugar
  • Obesity
  • Presence of other medical conditions, such as inflammatory bowel disease, chronic diarrhea, urinary tract infections, and hyperparathyroidism
  • Postmenopause/low estrogen levels in women

Kidney stones are composed of minerals and salt typically found in the urine in the kidneys or the tubes that drain urine from the kidney to the bladder (ureters). During the summer, people can become dehydrated, and they may drink large amounts of iced tea to combat it. The combination can raise the risk of kidney stones in people prone to their formation.

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If you develop kidney stones, you may or may not experience symptoms, as the stones are so tiny in many people, they don't cause any problems. In others, however, symptoms may come on suddenly and include excruciating pain in the lower back and/or groin, abdomen, or side. The pain may be accompanied by nausea and vomiting, blood in the urine, fever, chills, and difficulty urinating.

How to prevent kidney stones
Milner recommended choosing other beverages to satisfy your thirst this summer, such as real lemonade (using real lemons, not a powder), because lemons are a rich source of citrates, which inhibit the formation of kidney stones. Plain or sparkling water with a twist of lemon or lime quenches the thirst as well.

People who are prone to developing kidney stones also should reduce their intake of foods high in oxalates, such as wheat germ, Swiss chard, chocolate, rhubarb, nuts, and spinach, and also limit their use of salt and meat. Foods that provide calcium, such as yogurt and leafy greens, are recommended because calcium reduces the amount of oxalate the body absorbs.

Some experts have questioned whether green tea presents the same risk as black tea; that is, could you drink iced green tea rather than iced black tea and avoid the risk of kidney stones? Although some research indicates green tea poses a risk of kidney stone formation as does black tea, a few studies present another side to the story.

A 2010 study in CrystEngComm, for example, reported that green tea causes the oxalate crystals to form less stable crystals. The authors concluded that "Our results suggest that drinking green tea might be a good habit for the prevention of human stone formation."

To be safe, however, the take-home message from the Loyola study when it comes to drinking iced tea this summer comes from Milner: "don't overdo it. As with so many things involving a healthy lifestyle, moderation is key," so go easy on the iced tea and give your kidneys a break.

SOURCES:
Chen Z et al. Modulation of calcium oxalate crystallization by commonly consumed green tea. CrystEngComm 2010; 122:845.
Loyola University Stritch School of Medicine

Image: Wikimedia Commons

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