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Title: MAGNESIUM KINETICS IN ADOLESCENT GIRLS DETERMINED USING STABLE ISOTOPES: EFFECTS OF HIGH AND LOW CALCIUM INTAKE

Author
item SOJKA, JANICE - PURDUE UNIVERSITY
item WASTNEY, MERYL - GEORGETOWN UNIV. MED. CTR
item Abrams, Steven
item LEWIS, SARAH - PURDUE UNIVERSITY
item MARTIN, BERDINE - PURDUE UNIVERSITY
item WEAVER, CONNIE - PURDUE UNIVERSITY
item PEACOCK, MUNRO - INDIANA SCHOOL OF MED.

Submitted to: American Journal of Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Interactions between magnesium and calcium occur, but the mechanisms are not well understood. Human studies on the effect of high calcium intake on magnesium absorption have yielded contradictory results, so we decided to investigate this. We measured magnesium kinetics in adolescent girls participating in a calcium balance study, and taking in high amounts of calcium. We gave them both oral and intravenous stable isotopes of magnesium. The results, based on analysis of blood, urine and feces, showed that high calcium intake did not alter magnesium kinetics or balance in these adolescent girls. Our study established parameter values for magnesium kinetics in teenage girls based on the results we obtained after the dual-isotope administration.

Technical Abstract: Magnesium kinetics were measured in five adolescent girls who were participating in a calcium balance study. Two calcium levels were fed in a randomized crossover design. After an acclimation period, 26Mg was consumed orally and 25Mg was given intravenously, and then blood, urine, and feces were collected for 14 days. Total magnesium and percent enrichment were determined, and data were fitted to an eight-compartment model. There was no significant difference between high and low calcium intakes for any of the parameters examined. Mean values for control (800 mg/day) and high (1,800 mg/day) calcium intake were as follows: Mg intake, 305 +/- 30 and 286 +/- 9 mg/day; absorption (percent), 44 +/- 7 and 39 +/- 9; absorption (mg/day), 134 +/- 35 and 110 +/- 28; urinary excretion, 96 +/- 22 and 101 +/- 31 mg/day; fecal excretion, 175 +/- 32 and 200 +/- 11 mg/day; and magnesium balance, 13 +/- 35 and -34 +/- 48 mg/day, respectively. In conclusion, high calcium intake did not alter magnesium kinetics or balance in adolescent girls.