People who can't drink coffee, who are prone to kidney stones, should limit caffeine intake.

People who are prone to kidney stones should limit their caffeine intake, or they are more likely to develop kidney stones, according to a new study. When researchers gave some people with a history of kidney stones the equivalent of caffeine in two cups of coffee, they found a significant increase in calcium in their urine.

Linda Marcel of the University of Washington explains that calcium is an important component of stones, and their risk of developing kidney stones increases with excessive caffeine intake and an increase in the amount of calcium in their urine. Patients with stones should limit their caffeine intake, drink less than two cups of coffee a day, and consume less caffeine through other drinking methods than the same dose. How much is two cups? Dr. Linda said it should be 16 ounces, or two coffee pots, and beyond that, there is a risk of stones.

Previous studies have shown that people without stone tendencies also secrete more calcium after consuming caffeine, but does this also apply to people who are prone to stones? In response, Linda and Dr. Rogge Sutton of Columbia University conducted an experiment. They fasted 39 patients with stones and healthy people who had never had stones for 14 hours, and then asked them to drink water with caffeine. The researchers tested their urine two hours before and after they consumed caffeine, according to the researchers' report published in the journal Urology. Their urine levels of calcium, sodium, magnesium and citric acid all increased, suggesting that people who had never had kidney stones also had an increase in calcium secretion after taking caffeine.