Summer is high season for drinking iced tea. However, a John Miller, Loyla University Medical Center urologist warns that iced tea can contribute to painful kidney stones because of its high concentration of oxalate, one of the key chemicals that lead to the formation of kidney stones.

Around 10% of people in the U.S. suffer from kidney stones, a common disorder of the urinary tract.

Dr. John Milner, assistant professor at the Department of Urology at Loyola University Chicago Stritch School of Medicine explains: “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.”

Drinking an insufficient amount of fluids is the most common cause of kidney stones, and during the summer, when people can become dehydrated from sweating, the combined effect of dehydration together with drinking a lot of iced tea can raise the chance of developing kidney stones, particular in those already at risk.

Milner said:

“People are told that in the summertime they should drink more fluids. 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.”

Even though hot tea also contains oxalate, Milner said that it is difficult to drink sufficient amounts to cause kidney stones and figures from the Tea Association of the USA reveal that around 85% of tea consumed in the United States is iced.

In comparison with women, men are four times more likely to develop kidney stones, and the risk rises dramatically for those aged 40 years or older. Women with low estrogen levels like postmenopausal women and those with their ovaries removed are also at a higher risk.

Kidney stones are small mineral and salt crystals that are typically deposited in the urine in the kidneys or ureters, the small tubes that transport the urine from the kidney to the bladder. Usually kidney stones are so small they are expelled in the urine without causing any harm. However, sometimes the stones grow large enough to get lodged in the ureters, causing pain and discomfort.

Milner recommends drinking water or real lemonade, not the powdered version to quench thirst and properly hydrate as the best option, saying: “Lemons are high in citrates, which inhibit the growth of kidney stones.”

He also recommends that those who are at risk for kidney stones should reduce certain foods that contain high concentrations of oxalates, including spinach, chocolate, rhubarb and nuts and eat less salt and meat, drink several glasses of water a day and eat foods that provide adequate amounts of calcium as this reduces the amount of oxalate the body absorbs.

For those drinking iced tea, who already suffering from kidney stones, Milner advises to consult a specialist to see if the drink could be a contributing factor, as it fairly simple to check an overproduction of oxalates.

Milner advises: “Like many people, I enjoy drinking iced tea in the summer. But don’t overdo it. As with so many things involving a healthy lifestyle, moderation is key.”

Written by Petra Rattue