August 7/Chicago/Loyola University -- A urologist at Loyola University Medical Center in Chicago warns consumers that iced tea contains high concentrations of oxalate, one of the key chemicals that can lead to kidney stones.

Though in healthy bodies kidney stones -- small crystals made up of minerals and salts found in the urine of kidneys or ureters -- are expelled naturally from the body, stones can grow large enough to become lodged in the small tubes that drain urine from the kidney to the bladder.

Men are four times more likely to develop kidney stones than women, and the risk rises over the age of 40. Postmenopausal women with low estrogen levels and women who have had their ovaries removed are also at increased risk.

One of the most common causes is dehydration. And summer heat coupled with the overconsumption of iced tea can increase the risk, said Dr. John Milner in a statement released last week.

“People are told that in the summertime they should drink more fluids,” Milner said in a statement. “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.”

Other foods that contain high amounts of oxalates and should be consumed in moderation for people at risk include spinach, chocolate, rhubarb and nuts, he added.

Though water is the best choice, freshly squeezed lemonade -- not the powdered form -- can also inhibit the growth of kidney stones given its high levels of citrates.