Too Much of a Good Vitamin

Kidney stones more likely to develop with high ascorbic acid intake

(RxWiki News) Vitamin supplements can be good for you, but even too much of a good thing can be bad. Too much vitamin C can increase the risk of kidney stones in men.

Men who took high doses of vitamin C (ascorbic acid) were more than twice as likely to develop kidney stones compared to men who didn't, researchers found.

According to this study's authors, high doses of ascorbic acid supplements should be avoided. They suggested that those with a history of kidney stones ought to be especially careful with these supplements.

"Be aware of your vitamin intake."

Laura Thomas, MSc, from the Institute of Environmental Medicine, Division of Nutritional Epidemiology, led a study looking into whether ascorbic acid supplements were linked with kidney stones in men.

The study included 48,850 men between 45 and 79 years of age who were part of the Cohort of Swedish Men (COSM). The men had their first case of kidney stones between January 1998 and December 2009.

Participants were surveyed on their diet and lifestyle characteristics. The men specifically listed their supplemental use of ascorbic acid, particularly 1,000 milligrams of the vitamin, and 20 other dietary supplements.

Men who had improbable energy intake, a pre-baseline cancer diagnosis or missing data prior to the start of the study were excluded. Men who had previously had kidney stones were also excluded.

The researchers found 436 first cases of kidney stones among men during the course of their study.

The chance of having kidney stones increased more than two-fold among those who took more than seven tablets of ascorbic acid each week, the researchers found.

Further, those who took less than seven tablets of ascorbic acid were still one and a half times more likely of developing kidney stones compared to those who didn't take the supplements.

"In conclusion, our results indicate that high-dose ascorbic acid supplements—one of the most commonly used vitamin preparations—are associated with a dose-dependent two-fold increased risk of kidney stone formation among men," the researchers wrote in their report.

Multivitamin use was not tied to an increased risk of kidney stones.

The risk linked with ascorbic acid could depend on the combination of nutrients consumed with the supplement and the dose size itself, according to researchers.

The findings can't be generalized to women as they typically have a lower kidney stone risk, according to the researchers.

The study was published in the March 11, 2013 issue of the journal JAMA Internal Medicine. The Swedish Research Council/Research Infrastructures and Karolinska Institutet KID funding supported the study.

No conflicts of interest were declared.

Review Date: 
June 15, 2013