In pharmacokinetic comparisons, between MgGlycinate and MgOxide

[zack lim]

Here is what clinical studies and pharmacokinetic comparisons show:

1. Fractional Absorption
• Magnesium Oxide
• Has ~60% elemental magnesium by weight.
• But studies show only ~4% absorption (Firoz & Graber, Magnesium Research, 2001).
• For example, a 400 mg magnesium oxide tablet (240 mg elemental magnesium) yields only ~9.6 mg absorbed.
• Magnesium Glycinate
• Contains ~14% elemental magnesium.
• Absorption rates are much higher (commonly cited between 70–80%), largely due to amino acid chelation and transport via peptide/amino acid carriers (Coudray et al., Magnesium Research, 2005).
• A 400 mg magnesium glycinate capsule (56 mg elemental magnesium) may yield ~40–45 mg absorbed, which is >4x more than magnesium oxide for the same dosage weight.

2. Bioavailability Studies
• Walker et al., 2003 (Journal of the American College of Nutrition)
• Compared magnesium oxide, citrate, and amino acid chelates (like glycinate).
• Serum magnesium increased significantly more with glycinate and citrate than with oxide.
• Schuette et al., 1994 (Journal of the American College of Nutrition)
• Magnesium oxide showed minimal change in serum magnesium and urinary magnesium excretion (indicator of absorbed magnesium), while chelated forms like glycinate were significantly better.

3. Practical Impact
• Magnesium oxide is often used as a laxative or antacid because of its poor absorption.
• Magnesium glycinate is preferred for correcting magnesium deficiency and for people who need better GI tolerance.

Bottom line:
Despite magnesium oxide having more elemental magnesium, its poor solubility and limited absorption mechanisms result in much lower actual bioavailability. Magnesium glycinate, being a chelate, uses amino acid transport pathways and dissolves better, leading to significantly greater absorption and better physiological effect.



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