Q. I have a friend who was told she probably got her kidney stones from taking vitamin C and calcium supplements. There isn’t a daily vitamin supplement out there that doesn’t contain one or the other, if not both. What’s the story on this?
A. The story is complicated, because the studies have given contradictory results. Calcium supplements appear to increase the risk of kidney stones (American Journal of Clinical Nutrition, Jul. 2011).
Some people make more kidney-stone forming oxalate after large doses (2,000 mg) of vitamin C (Journal of Nutrition, Jul. 2005). The amount you would get from a multi-vitamin, however, is not likely to cause problems.
