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Circulating Ionized Magnesium as a Measure of Supplement Bioavailability: Results from a Pilot Study for Randomized Clinical Trial

Public Health Nutrition, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
Department of Nutrition and Food Studies, George Mason University, MS1F7, 4400 University Drive, Fairfax, VA 22030, USA
Think Healthy Group, Inc., 1301 20th Street NW, Washington, DC 20036, USA
Center for Magnesium Education & Research, 13-1255 Malama Street, Pahoa, HI 96778, USA
Department of Nutrition Science, Purdue University, 700 West State Street, West Lafayette, IN 47907, USA
Department of Applied Health Science, School of Public Health, Indiana University Bloomington, Bloomington, IN 47405, USA
Weaver and Associates Consulting, LLC, West Lafayette, IN 47906, USA
Author to whom correspondence should be addressed.
Nutrients 2020, 12(5), 1245;
Received: 24 March 2020 / Revised: 9 April 2020 / Accepted: 22 April 2020 / Published: 28 April 2020
(This article belongs to the Special Issue Magnesium in Human Health and Disease)
Oral supplementation may improve the dietary intake of magnesium, which has been identified as a shortfall nutrient. We conducted a pilot study to evaluate appropriate methods for assessing responses to the ingestion of oral magnesium supplements, including ionized magnesium in whole blood (iMg2+) concentration, serum total magnesium concentration, and total urinary magnesium content. In a single-blinded crossover study, 17 healthy adults were randomly assigned to consume 300 mg of magnesium from MgCl2 (ReMag®, a picosized magnesium formulation) or placebo, while having a low-magnesium breakfast. Blood and urine samples were obtained for the measurement of iMg2+, serum total magnesium, and total urine magnesium, during 24 h following the magnesium supplement or placebo dosing. Bioavailability was assessed using area-under-the-curve (AUC) as well as maximum (Cmax) and time-to-maximum (Tmax) concentration. Depending on normality, data were expressed as the mean ± standard deviation or median (range), and differences between responses to MgCl2 or placebo were measured using the paired t-test or Wilcoxon signed-rank test. Following MgCl2 administration versus placebo administration, we observed significantly greater increases in iMg2+ concentrations (AUC = 1.51 ± 0.96 vs. 0.84 ± 0.82 mg/dL•24h; Cmax = 1.38 ± 0.13 vs. 1.32 ± 0.07 mg/dL, respectively; both p < 0.05) but not in serum total magnesium (AUC = 27.00 [0, 172.93] vs. 14.55 [0, 91.18] mg/dL•24h; Cmax = 2.38 [1.97, 4.01] vs. 2.24 [1.98, 4.31] mg/dL) or in urinary magnesium (AUC = 201.74 ± 161.63 vs. 139.30 ± 92.84 mg•24h; Cmax = 26.12 [12.91, 88.63] vs. 24.38 [13.51, 81.51] mg/dL; p > 0.05). Whole blood iMg2+ may be a more sensitive measure of acute oral intake of magnesium compared to serum and urinary magnesium and may be preferred for assessing supplement bioavailability. View Full-Text
Keywords: magnesium; iMg; biomarkers; nutritional status; diet magnesium; iMg; biomarkers; nutritional status; diet
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Zhan, J.; Wallace, T.C.; Butts, S.J.; Cao, S.; Ansu, V.; Spence, L.A.; Weaver, C.M.; Gletsu-Miller, N. Circulating Ionized Magnesium as a Measure of Supplement Bioavailability: Results from a Pilot Study for Randomized Clinical Trial. Nutrients 2020, 12, 1245.

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