Association of Dietary Magnesium (Mg2+) and Potassium (K+) Intake with Mortality and Kidney Failure in the CRIC Study

Background: Increased intake of Mg2+ and K+ are each linked to lower risk of cardiovascular outcomes and death. While studies have shown improved kidney outcomes with increased dietary intake of Mg2+ or K+, data is limited in CKD patients. Methods: Using Chronic Renal Insufficiency Cohort data, we included subjects with baseline dietary surveys and a follow up measure of eGFR (n = 3318). Estimated daily Mg2+ (including supplemental) and K+ intake were examined as predictors for subsequent death or kidney failure*. Our final statistical model^ was repeated and stratified into groups of eGFR < 30 and ≥ 30 ml/min. Results: The median intake (mg/day) was 312 for Mg2+ and 2636 for K+. Higher Mg2+ and K+ intake were associated with a lower risk for death (Fig 1 a&c). Stratified analyses showed a similar relationship regardless of eGFR group (Fig 2 a&c). Mg2+ or K+ intake had no consistent relationship with kidney failure in the total cohort (Fig 1 b&d), but each appeared protective for kidney failure only in the eGFR ≥ 30 ml/min subgroup (Fig 2 b&d). Conclusion: Our data suggest Mg2+ and K+ intake are protective against death in CKD patients, regardless of degree of kidney disease. While not statistically significant in all models, our data also suggest both Mg2+ and K+ intake may be protective against kidney failure, but only in those with an eGFR ≥ 30 ml/min. Future research should study the benefits or potential harms of Mg2+ and/or K+ supplementation in CKD patients.