Relationship between short-term self-reported dietary magnesium intake and whole blood ionized magnesium (iMg) or serum magnesium (s-Mg) concentrations.

Objective: Since we and others have shown that supplemental magnesium raises whole blood ionized magnesium (iMg) we investigated the relationships between self-reported dietary magnesium intake and concentrations of whole blood iMg and serum magnesium (s-Mg).

Methods: We obtained whole blood iMg concentrations, as well as s-Mg concentrations, from a pilot, three-arm, randomized, controlled, crossover bioavailability study of magnesium supplements ( = 23; 105 measures). Dietary magnesium intake was assessed using three-day food records and the Nutrition Data System for Research (NDSR, University of Minnesota, MN, USA). Whole blood iMg was measured with an electrode analyser (NOVA Biochemical, Waltham, MA, USA), whereas s-Mg was measured using atomic absorption spectroscopy. A linear mixed-effects model was employed with dietary magnesium as the outcome variable and iMg, s-Mg, study treatment and study visit as fixed effects. We adjusted age, gender, race and body mass index covariates.

Results: Values for dietary magnesium, iMg and s-Mg were 303.8 ± 118.9 mg/day, 1.3 ± 0.1 mg/dL and 2.2 ± 4.1 mg/dL, respectively. No association was found between dietary magnesium intake and iMg -125 ± 176.95 ( = .49) or s-Mg -9.33 ± 5.04 ( = .08).

Conclusions: Whole blood iMg and s-Mg concentrations do not reflect short-term self-reported dietary intake in adults. Further research is needed to determine whether blood biomarkers of magnesium may reflect dietary magnesium intake.Key messagesDietary intake of magnesium, a shortfall nutrient, may be objectively measured using blood biomarkers of magnesium.Serum magnesium and whole blood iMg were not associated with short-term dietary intake of magnesium.