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Ascorbic acid supplements use has been associated with kidney stone formation (2015-08-07)

High-dose ascorbic acid supplements — one of the most commonly used vitamin preparations — are associated with a dose-dependent 2-fold increased risk of kidney stone formation among men.

For this study 48 850 men, aged 45 to 79 years at baseline, were recruited in 1997 (response rate, 49%). Detailed diet and lifestyle data were collected at baseline using a self-administered questionnaire.
During 11 years of follow-up researchers ascertained 436 first incident cases of kidney stones.
Analysis of kidney stone material collected from 3176 men, treated with extracorporeal shockwave lithotripsy in Stockholm County, found calcium oxalate to be the dominant component in 92.6% (H.-G.T., unpublished data). It could thus be assumed that at least 90% of the kidney stones in this study population were composed primarily of calcium oxalate.
Vitamin C is excreted in urine both in its unmetabolized form and as oxalate.

The results may not be generalizable to women, who typically have a much lower kidney stone risk.
Because the risk associated with ascorbic acid may depend both on the dose and on the combination of nutrients with which the ascorbic acid is ingested, these findings should not be translated to dietary vitamin C.

Data on the brand of supplement used were not available, and the researchers were not, therefore, able to fully characterize the dose taken.
However, previous studies have demonstrated that ascorbic acid preparations available on the Swedish market typically contain 1000 mg of ascorbic acid per tablet.

Currently there are no well-documented benefits of high-dose ascorbic acid supplement use, and therefore, it seems prudent to advise that high-dose preparations be avoided, particularly by those with a history of kidney stones.

For more information
Ascorbic Acid Supplements and Kidney Stone Incidence Among Men: A Prospective Study
Laura D. K. Thomas, MSc; Carl-Gustaf Elinder, MD; Hans-Göran Tiselius, MD; Alicja Wolk, DrMedSc; Agneta Åkesson, PhD
AMA Intern Med. 2013;173(5):386-388.
doi:10.1001/jamainternmed.2013.2296

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