Use of ascorbic acid supplements may increase the risk of kidney stones in men, according to data published online ahead of print in JAMA Internal Medicine.

In a prospective population-based study of men who participated in the Cohort of Swedish Men, Laura D. K. Thomas, MSc, of the Karolinska Institutet in Stockholm, Sweden, and colleagues identified 436 new kidney stone cases during 11 years of follow-up. Compared with non-users of ascorbic acid supplements, users had a significant twofold increased risk of kidney stones; multivitamin use was not associated with kidney stone risk. Users of only ascorbic acid taking fewer than seven tablets per week (median) had a significant 66% increased risk of kidney stones and users taking seven or more tablets per week had a significant 2.2 times increased risk in a fully adjusted model.

The researchers noted that a previous analysis of kidney stone material collected from 3,176 men treated with shockwave lithotripsy in Stockholm County found that calcium oxalate was the dominant component in 92.6% of cases. “It could thus be assumed that at least 90% of the kidney stones in our study population were composed primarily of calcium oxalate,” Dr. Thomas’ team wrote.

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