Dose-dependent effect seen with up to two-fold increased risk after multivariate adjustment
WEDNESDAY, Feb. 6 (HealthDay News) -- High-dose ascorbic acid supplements are associated with a significantly increased risk of kidney stone formation in men, according to a research letter published online Feb. 4 in JAMA Internal Medicine.
To examine the correlation between ascorbic acid supplements and kidney stones, Laura D.K. Thomas, from the Karolinska Institutet in Stockholm, and colleagues used diet and lifestyle data collected via a self-administered questionnaire completed by participants in the Cohort of Swedish Men. Participants reported their use of ascorbic acid and of 20 other supplement types. Men diagnosed with kidney stones prior to baseline (based on registry or self-reported data) were excluded.
During 11 years of follow-up, the researchers found that there were 436 first incident cases of kidney stones. Ascorbic acid use correlated with a significantly increased risk of kidney stones (age-adjusted relative risk [RR], 1.90; full multivariate adjusted RR, 1.95). There was no significant correlation between multivitamin use and kidney stone risk. In the full multivariate-adjusted model, the increased relative risk of kidney stones was seen in users of only ascorbic acid taking fewer than seven (RR, 1.66) and seven or more tablets per week (RR, 2.23), compared with supplement nonusers.
"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 authors write.
Full Text (subscription or payment may be required)