Whole Blood Ionized Magnesium, a Novel Nutrition Biomarker for Magnesium Intake

Abstract

Objectives Most studies used serum magnesium concentration and total urine magnesium as nutrition biomarkers of magnesium, but whether these biomarkers are sensitive to changes in dietary intake of magnesium is uncertain. Whole blood ionized magnesium (iMg2+) is the free bioactive form of magnesium in the body, and therefore it could be more sensitive to the changes in magnesium intake. Thus, we aimed to compare the responses of iMg2+, serum magnesium concentration, and total urine magnesium following an oral dose of magnesium. Methods Healthy adults participated in a randomized, single-blind, placebo-controlled crossover trial. They were randomly assigned to 300 mg of magnesium chloride (MgCl2, ReMag®) or placebo, taken with a low-magnesium breakfast after 8-hours of fasting. Timed blood and urine samples were obtained beginning 15-minutes before breakfast, and then at 0, 0.5, 1, 2, 4, 6, 8, and 24-hours timepoints following breakfast. Pharmacokinetic analyses included area under the curve (AUC), the maximum concentration (Cmax), and the time to maximum concentration (Tmax) for iMg2+, serum magnesium concentration, and total urine magnesium. Data were analyzed using paired t-test and Wilcoxon signed-rank test, and reported as mean ± standard deviation, or as median and range, depending on normality. Results Seventeen participants were included in the data analyses. Responses were observed following MgCl2 compared to placebo for iMg2+ (AUC = 1.51 ± 0.96 vs. 0.84 ± 0.82, and Cmax = 1.38 ± 0.13 vs. 1.32 ± 0.07, both P < 0.05). We saw no response following MgCl2 versus placebo for serum magnesium concentration (AUC = 27.00 [0, 172.93] vs. 14.55 [0, 91.18], and Cmax = 2.38 [1.97, 4.01] vs. 2.24 [1.98, 4.31]), and for total urine magnesium (AUC = 201.74 ± 161.63 vs. 139.30 ± 92.84, and Cmax = 26.12 [12.91, 88.63] vs. 24.38 [13.51, 81.51]), both P > 0.05. Conclusions The response of iMg2+ to a single oral dose of magnesium was more pronounced than the responses of serum magnesium concentration and total urine magnesium. Therefore, iMg2+ may be a more sensitive nutrition biomarker for magnesium intake. Funding Sources Funding for this study was provided through an unrestricted educational grant from Think Healthy Group Inc.