What Really Causes Kidney Stones (And Why Vitamin C Does Not)Submitted by Bob-45 on Tue, 02/12/2013 - 00:59
FOR IMMEDIATE RELEASE
Orthomolecular Medicine News Service, February 11, 2013
What Really Causes Kidney Stones
(And Why Vitamin C Does Not)
(OMNS Feb 11, 2013) A recent widely-publicized study claimed that vitamin C supplements increased the risk of developing kidney stones by nearly a factor of two. The study stated that the stones were most likely formed from calcium oxalate, which can be formed in the presence of vitamin C (ascorbate), but it did not analyze the kidney stones of participants. Instead, it relied on a different study of kidney stones where ascorbate was not tested. This type of poorly organized study does not help the medical profession or the public, but instead causes confusion.
The study followed 23,355 Swedish men for a decade. They were divided into two groups, one that did not take any supplements (22,448), and another that took supplements of vitamin C (907). The average diet for each group was tabulated, but not in much detail. Then the participants who got kidney stones in each group were tabulated, and the group that took vitamin C appeared to have a greater risk of kidney stones. The extra risk of kidney stones from ascorbate presented in the study is very low, 147 per 100,000 person-years, or only 0.15% per year.
Key points the media missed:
The number of kidney stones in the study participants who took ascorbate was very low (31 stones in over a decade), so the odds for statistical error in the study are fairly high.
The study was observational. It simply tabulated the intake of vitamin C and the number of kidney stones to try to find an association between them.
This method does not imply a causative factor because it was not a randomized controlled study, that is, vitamin C was not given to a group selected at random.
This type of observational study is fraught with limitations that make its conclusion unreliable.
It contradicts previous studies that have clearly shown that high dose ascorbate does not cause kidney stones.[2-6]
The study authors' conclusion that ascorbate caused the low rate of stones is likely due to a correlation between the choice of taking a vitamin C supplement with some other aspect of the participants' diet.
The study could not determine the nature of this type of correlation, because it lacked a detailed study of each patient's diet and a chemical analysis of each stone to provide a hint about the probable cause.