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Magnesium bioavailability from magnesium citrate and magnesium oxide
J S Lindberg1, M M Zobitz, J R Poindexter
1Center for Mineral Metabolism and Clinical Research, University of Texas, Southwestern Medical Center, Dallas 75235.
Journal of the American College of Nutrition
|February 1, 1990
Summary
Magnesium citrate demonstrates superior in vitro solubility and in vivo gastrointestinal absorbability compared to magnesium oxide. This suggests magnesium citrate is a more bioavailable magnesium supplement.
Area of Science:
- Biochemistry
- Pharmacology
- Human Physiology
Background:
- Magnesium is an essential mineral involved in numerous physiological processes.
- Dietary magnesium bioavailability can be influenced by its chemical form.
- Understanding the solubility and absorption of different magnesium compounds is crucial for nutritional science.
Purpose of the Study:
- To compare the in vitro solubility of magnesium citrate and magnesium oxide.
- To assess the in vivo gastrointestinal absorbability of magnesium citrate and magnesium oxide.
- To determine which magnesium salt offers better bioavailability.
Main Methods:
- In vitro solubility testing of magnesium citrate and magnesium oxide in varying hydrochloric acid concentrations (0-24.2 mEq).
- Assessment of magnesium salt reprecipitation after simulated pancreatic bicarbonate secretion.
- In vivo measurement of urinary magnesium levels in normal volunteers following oral administration of magnesium citrate and magnesium oxide loads.
Main Results:
- Magnesium oxide exhibited low solubility (43%) even in simulated peak acid conditions, while magnesium citrate showed high solubility (55%) in water alone.
- Magnesium citrate remained soluble and formed soluble complexes, unlike magnesium oxide.
- Urinary magnesium excretion was significantly higher after magnesium citrate intake compared to magnesium oxide, indicating greater absorption.
Conclusions:
- Magnesium citrate is significantly more soluble in vitro than magnesium oxide across a range of acid conditions.
- Magnesium citrate exhibits superior in vivo gastrointestinal absorbability and bioavailability compared to magnesium oxide.
- These findings support magnesium citrate as a more effective form for magnesium supplementation.