May 2/Chicago/Right Vision News --Men over 40 may want to avoid iced tea and start hitting the lemonade if they wish to lower their risk of kidney stones, according to experts.

Kidney stones, crystals that develop in the kidneys or the tubes that carry urine from the kidney to the bladder, affect 10% of the U.S. population, and men run a four times greater risk than women of developing them. The chance of forming kidney stones rises steeply after the age of 40.

Oxalate, a key chemical in the formation of kidney stones, comes in high concentrations in iced tea.

"For many people, iced tea is potentially one of the worst things they can drink," John Milner, an instructor in the department of urology at Loyola University Chicago Stritch School of Medicine, said in a news release. "For people who have a tendency to form kidney stones, it's definitely one of the worst things you can drink."

The failure to stay hydrated is a common cause of kidney stones. Summertime heat and humidity, which causes excessively sweating and dehydration, combined with an marked increase in iced tea consumption in the U.S., raises the risk of kidney stones during this time of year.

The Tea Association of the U.S.A. reports that Americans consume almost 1.91 billon gallons of iced teas a year, a dramatic rise presumably driven by the belief that the beverage is healthier than other alternatives such as soda and beer.

Milner said drinking water is the best way to stay properly hydrated, but if one is prone to developing kidney stones, flavoring water heavily with lemon or drinking lemonade may help.

From the May 10, 2010, Prepared Foods E-dition