Journal of the American College of Nutrition, Vol 13, Issue 5 447-454, Copyright © 1994 by American College of Nutrition

CLINICAL TRIAL

Comparative effects of a Mg-enriched diet and different orally administered magnesium oxide preparations on ionized Mg, Mg metabolism and electrolytes in serum of human volunteers

B. T. Altura, C. Wilimzig, T. Trnovec, S. Nyulassy and B. M. Altura
Department of Physiology, State University of New York, Brooklyn, New York.

OBJECTIVE: To determine whether: 1) short-term dietary elevation in magnesium (Mg) intake could alter serum ionized Mg (IMg2+), total Mg (TMg); % ionized Mg (% IMg2+) and other cations; and 2) different formulated preparations of Mg oxide (MgO) in the presence and absence of phosphate could alter serum IMg2+, TMg, % IMg2+ and other cations in Mg-loaded subjects. METHODS: A randomized, triple cross-over study was performed on a rigorously defined group of normal male volunteers. Eighteen males were administered diets containing four to five times the United States recommended daily allowance (USRDA) of Mg followed by a randomization of three different MgO preparations, in the presence or absence of phosphate, containing equimolar amounts (12.34 mmol) of elemental Mg. Forty age-matched volunteers served as reference range controls. Specific ion selective electrodes were utilized to measure IMg2+, ionized calcium (ICa2+), sodium (Na+) potassium (K+) and hydrogen ion concentration (H+). Measurement of urinary excretion of Mg as well as TMg were determined by atomic absorption spectroscopy. RESULTS: Diets enriched with different oral formulations of Mg given for 6 days result in significant elevations in serum IMg2+ and % IMg2+ but not TMg, ICa2+, K+ or H+ in normal subjects. Although such Mg-loaded subjects demonstrate significant elevation in urinary excretion of Mg, no further changes in IMg2+, TMg or any of the serum cations were produced by ingestion of either of the three MgO preparations. Subjects showing normally low basal levels of serum IMg2+, (< or = 0.54 mM/L), could easily have their serum IMg2+ level manipulated by diets enriched with Mg, whereas subjects having average normal or high normal IMg2+ levels did not have their IMg2+ elevated significantly with either diets enriched with Mg or with exogenous MgO. CONCLUSION: These results indicate that since serum IMg2+ and % IMg2+, but not TMg, can be altered by dietary intake, previous or future findings which may indicate no change in TMg by diet may not reflect changes in biologically-active Mg.

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