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.
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.


CONCLUSIONS
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.
Department of Physiology, State University of New York, Brooklyn, New York.
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Altura
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Wilimzig
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Trnovec
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Nyulassy
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D000293:Adolescent; D000328:Adult; D002118:Calcium / Q000097:blood; D002413:Cations, Divalent; D018592:Cross-Over Studies; D004032:Diet; D006801:Humans; D008274:Magnesium / Q000008:administration & dosage* / Q000097:blood* / Q000494:pharmacology; D008277:Magnesium Oxide / Q000008:administration & dosage* / Q000494:pharmacology; D008297:Male; D011188:Potassium / Q000097:blood; D011522:Protons; D012016:Reference Values; D012964:Sodium / Q000097:blood
D002413:Cations, Divalent; D011522:Protons; D008277:Magnesium Oxide; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium