High dietary magnesium intake decreases hyperoxaluria in patients with nephrolithiasis

To examine the relationship between urine magnesium and hyperoxaluria in a cohort of patients with recurrent stone formation.

A total of 311 patients with nephrolithaisis were evaluated. The patients were divided into quintiles of urine magnesium excretion, an accepted surrogate of dietary magnesium intake. Multivariate analysis was used to examine the relationship between magnesium and hyperoxaluria.

The mean patient age was 50.0 ± 14.9 years, the body mass index was 28.0 ± 5.9 kg/m(2), and 130 were women and 181 were men. The mean urine magnesium excretion was 100.8 ± 42.0 mg/d (range 17.8-224.8). On multivariate analysis, an increasing quintile of urine magnesium was associated with decreasing hyperoxaluria (β = -0.37, 95% confidence interval -0.6 to -0.14, P < .05 for trend). When analyzed as separate quintiles with the lowest quintile of magnesium as the referent, only the greatest quintile demonstrated a statistically significant decrease in hyperoxaluria (β = -1.7, 95% confidence interval -2.7 to -0.7, P < .05 for trend).

Increasing magnesium intake was associated with decreasing hyperoxaluria in this population of patients with stone formation. Our findings showed that high magnesium intake might be required to observe clinically significant effects from magnesium.