Ascorbic Acid Ups Kidney Stone Risk

STOCKHOLMAscorbic acid supplements were associated with a higher risk of kidney stones in Swedish men, according to a new study published in JAMA Internal Medicine. Using the Cohort of Swedish Men, researchers had access to nearly 49,000 patients who provided detailed lifestyle and diet information (Arch Intern Med. 2013;173(2):1-2. doi:10.1001/jamainternmed.2013.2296). In the 11 years of follow-up, scientists noted 436 incidents of kidney stones.

Median ascorbic acid use was associated with a two-fold increased risk. Subjects taking less than seven tablets a week recorded a 1.66 relative risk (RR), compared to the 2.23 RR of taking more than seven tablets weekly. Researchers noted the average ascorbic acid supplement in Sweden contains 1000 mg of ascorbic acid. Multivitamin users did not experience an increased kidney stone risk.

"This certainly isnt the first time weve seen this possible association, but most experts believe the beneficial effects of vitamin C outweigh the possible adverse effects," said Cara Welch, Ph.D., Natural Products Association (NPA) vice president of scientific and regulatory affairs. "The accumulated evidence on vitamin C demonstrates that, even at the high doses in this study, it is a remarkably safe substance."