Dietary magnesium supplementation in cats with chronic kidney disease: A prospective double-blind randomized controlled trial.

Abstract

BACKGROUND: Plasma total magnesium concentration (tMg) is a prognostic indicator in cats with chronic kidney disease (CKD), shorter survival time being associated with hypomagnesemia. Whether this risk factor is modifiable with dietary magnesium supplementation remains unexplored. OBJECTIVES: Evaluate effects of a magnesium-enriched phosphate-restricted diet (PRD) on CKD-mineral bone disorder (CKD-MBD) variables. ANIMALS: Sixty euthyroid client-owned cats with azotemic CKD, with 27 and 33 allocated to magnesium-enriched PRD or control PRD, respectively. METHODS: Prospective double-blind, parallel-group randomized trial. Cats with CKD, stabilized on a PRD, without hypermagnesemia (tMg >2.43&#x2009;mg/dL) or hypercalcemia (plasma ionized calcium concentration, (iCa) >6&#x2009;mg/dL), were recruited. Both intention-to-treat and per-protocol (eating &#x2265;50% of study diet) analyses were performed; effects of dietary magnesium supplementation on clinicopathological variables were evaluated using linear mixed effects models. RESULTS: In the per-protocol analysis, tMg increased in cats consuming a magnesium-enriched PRD (&#x3b2;, 0.25&#x2009;&#xb1;&#x2009;.07&#x2009;mg/dL/month; P&#x2009;<&#x2009;.001). Five magnesium supplemented cats had tMg >2.92&#x2009;mg/dL, but none experienced adverse effects. Rate of change in iCa differed between groups (P&#x2009;=&#x2009;.01), with decreasing and increasing trends observed in cats fed magnesium-enriched PRD and control PRD, respectively. Four control cats developed ionized hypercalcemia versus none in the magnesium supplemented group. Log-transformed plasma fibroblast growth factor-23 concentration (FGF23) increased significantly in controls (&#x3b2;, 0.14&#x2009;&#xb1;&#x2009;.05&#x2009;pg/mL/month; P&#x2009;=&#x2009;.01), but remained stable in the magnesium supplemented group (&#x3b2;, 0.05&#xb1;.06&#x2009;pg/mL/month; P&#x2009;=.37). CONCLUSIONS AND CLINICAL IMPORTANCE: Magnesium-enriched PRD is a novel therapeutic strategy for managing feline CKD-MBD in cats, further stabilizing plasma FGF23 and preventing hypercalcemia.