Effect of magnesium supplementation on the fractional intestinal absorption of 45CaCl2 in women with a low erythrocyte magnesium concentration

Metabolism. 2000 Aug;49(8):1092-6. doi: 10.1053/meta.2000.7711.


The cosupplementation of magnesium with calcium has been suggested to be beneficial in the prevention of osteoporosis. We investigated the effect of magnesium supplementation on parameters of bone resorption and fractional 45Ca absorption. Twenty apparently healthy women with a mean age of 39.2 +/- 9.2 years and an erythrocyte magnesium concentration less than 1.97 mmol/L were recruited into a controlled magnesium supplementation trial. During weeks 1 to 4, they received a daily control preparation, potassium/sodium citrate malate (PSCM). During weeks 5 to 8, the subjects received magnesium citrate malate (MCM) equivalent to 250 mg magnesium per day. During the fourth and eighth weeks, blood was collected for measurement of the serum intact parathyroid hormone (PTH) concentration and serum and erythrocyte magnesium concentration. Urine was collected for measurement of calcium, magnesium, creatinine, and deoxypyridinoline excretion. On the final day of each treatment period, 5 microCi45CaCl2 was administered orally, and the isotope was traced in the blood and urine over 7 hours. Urinary calcium, 45Ca, and deoxypyridinoline excretion, as well as serum intact PTH levels, showed no statistically significant changes as a result of magnesium supplementation. However, urinary magnesium excretion increased by 31.1% (P < .005) while fractional 45Ca absorption decreased by 23.5% (P < .001) as a result of magnesium supplementation. It is concluded that magnesium supplementation does not result in changes in bone resorption, while the fractional intestinal absorption of 45Ca appears to decrease.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amino Acids / urine
  • Bone Resorption / diet therapy
  • Bone Resorption / metabolism
  • Calcium / metabolism
  • Calcium / urine
  • Calcium Chloride / pharmacokinetics*
  • Calcium Radioisotopes*
  • Dietary Supplements*
  • Erythrocytes / drug effects
  • Erythrocytes / metabolism*
  • Female
  • Humans
  • Intestinal Absorption / drug effects*
  • Magnesium / administration & dosage*
  • Magnesium / adverse effects
  • Magnesium / blood*
  • Parathyroid Hormone / blood


  • Amino Acids
  • Calcium Radioisotopes
  • Parathyroid Hormone
  • deoxypyridinoline
  • Magnesium
  • Calcium Chloride
  • Calcium