Vitamin C supplements tied to men's kidney stones: study
"It has long been suspected that high doses of vitamin C may increase the risk of kidney stones as some of the vitamin C absorbed by the body is excreted in urine as oxalate, one of the key components of kidney stones," said lead researcher Laura Thomas at the Karolinska Institutet in Stockholm.
Thomas and her team, whose findings appeared in JAMA Internal medicine, used data from a large study of middle-aged and elderly Swedish men who answered a series of questions on their diet and lifestyle, then were tracked for an average of 11 years.
The current analysis included 907 men who said they took regular vitamin C tablets and more than 22,000 who didn't use any nutritional supplements.
Of the vitamin C users, 3.4 percent developed kidney stones for the first time during the study, compared to 1.8 percent of non-supplement users. Men who took vitamin C supplements at least once a day had the highest risk of kidney stones.
Stones are made up of tiny crystals, which can be formed by calcium combining with oxalate. They usually pass on their own, but can cause severe pain in the process, though larger stones occasionally require surgery.
The findings don't prove that the vitamin itself triggers stones to form. But researchers said that because there are no clear benefits tied to taking high-dose vitamin C, people who have had stones in
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