Magnesium bioavailability

On December 20, 2009, in Minerals, by Andrea

From Journal of The American College of Nutrition:


Magnesium bioavailability from magnesium citrate and magnesium oxide

J. S. Lindberg, M. M. Zobitz, J. R. Poindexter and C. Y. Pak
Center for Mineral Metabolism and Clinical Research, University of Texas, Southwestern Medical Center, Dallas 75235.

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 less than 0.05; during second 2 hours post-load, 0.035 vs 0.008 mg/mg creatinine, p less than 0.05). Thus, magnesium citrate was more soluble and bioavailable than magnesium oxide.

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3 Responses to “Magnesium bioavailability”

  1. penneynurse says:

    Where do you get your magnesium from? I have been taking mag from the local Walgreen, and just looked at the label, and sure enough it’s mag oxide. What brand do you get?

  2. Andrea says:

    I get mine from vitalady — and I can tell you, not a single “issue” with the citrate at all and I take it 2x a day.

    I almost miss that aspect of it some days…

  3. penneynurse says:

    I looked on and I see two different doses for the mag citrate, what is the recommended amount needed daily for post rny?

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