Caffeine increases kidney stones risk

People who are prone to kidney stones should limit their caffeine intake. An increase in urinary calcium increases the risk of stones because calcium is an important ingredient in kidney stones - so high levels are more likely to result in stones.Previous research has shown that people who do not tend to form kidney stones also excrete more calcium in their urine after consuming caffeine (found in tea, coffee, chocolate, caffeinated soft drinks, etc). Researchers from the University of British Columbia in Vancouver, Canada, investigated whether this was also true for people who were prone to stones. They asked 39 people with kidney stones and nine who never had stones to drink caffeine added to water after 14 hours of fasting. The researchers tested their urine 2 hours before and after they consumed caffeine. It was found that the stone-formers showed an increase in calcium, sodium, magnesium and citrate in their urine. The same pattern also occurred in the people with no history of kidney stones. The researchers explained that more calcium and sodium in urine increases the risk of kidney stones, while increases in magnesium and citrate appear to protect people from kidney stones.
The researchers recommended that stone sufferers should limit themselves to less than two cups of coffee per day or a comparable amount of caffeine from other sources.

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