Magnesium bioavailability from magnesium citrate and magnesium oxide

J. S. Lindberg, M. M. Zobitz, J. R. Poindexter, C. Y C Pak

Research output: Contribution to journalArticle

96 Scopus citations

Abstract

This study compared magnesium oxide and magnesium citrate with respect to in vitro solubility and in vivo gastrointestinal absorbability. The solubility of 25 mmol magnesium citrate and magnesium oxide was examined in vitro in solutions containing varying amounts of hydrochloric acid (0-24.2 mEq) in 300 ml distilled water intended to mimic achlorhydric to peak acid secretory states. Magnesium oxide was virtually insoluble in water and only 43% soluble in simulated peak acid secretion (24.2 mEq hydrochloric acid/300 ml). Magnesium citrate had high solubility even in water (55%) and was substantially more soluble than magnesium oxide in all states of acid secretion. Reprecipitation of magnesium citrate and magnesium oxide did not occur when the filtrates from the solubility studies were titrated to pH 6 and 7 to stimulate pancreatic bicarbonate secretion. Approximately 65% of magnesium citrate was complexed as soluble magnesium citrate, whereas magnesium complexation was not present in the magnesium oxide system. Magnesium absorption from the two magnesium salts was measured in vivo in normal volunteers by assessing the rise in urinary magnesium following oral magnesium load. The increment in urinary magnesium following magnesium citrate load (25 mmol) was significantly higher than that obtained from magnesium oxide load (during 4 hours post-load, 0.22 vs 0.006 mg/mg creatinine, p < 0.05; during second 2 hours post-load, 0.035 vs 0.008 mg/mg creatinine, p < 0.05). Thus, magnesium citrate was more soluble and bioavailable than magnesium oxide.

Original languageEnglish (US)
Pages (from-to)48-55
Number of pages8
JournalJournal of the American College of Nutrition
Volume9
Issue number1
DOIs
StatePublished - Feb 1 1990

Keywords

  • Hypocitraturia
  • Hypomagnesiuria
  • Magnesium
  • Nephrolithiasis
  • Solubility of salts

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Nutrition and Dietetics

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