Assessment of bioavailability of Mg from Mg citrate and Mg oxide by measuring urinary excretion in Mg-saturated subjects.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 32162607 · doi:10.1684/mrh.2019.0457
What was done
Fourteen healthy males underwent a 5-day saturation phase with 400 mg magnesium daily before receiving a single 400 mg dose of magnesium from either magnesium citrate (MgC) or magnesium oxide (MgO). Bioavailability was evaluated by measuring renal magnesium excretion in 24-hour urine and blood plasma magnesium concentrations at 0, 2, 4, 8, and 24 hours.
What was found
Single-dose MgC produced a statistically significant (P < 0.05) increase in 24-hour urinary magnesium excretion, whereas the increase following MgO was not statistically significant. Plasma magnesium concentrations were significantly higher for MgC compared to MgO at 4 hours (P < 0.05) and 8 hours (P < 0.05). Compared with baseline, MgC led to a significant increase in plasma magnesium at all measured time points, whereas MgO did not. The abstract provides P-values but reports no absolute numbers, means, or standard deviations.
Why it matters
This study provides evidence supporting the superior acute bioavailability of organic magnesium citrate over inorganic magnesium oxide in magnesium-saturated subjects.
Limits
The sample size was very small (14 participants) and restricted entirely to healthy males. Exact numerical measurements and effect sizes are omitted from the abstract. The study only evaluated acute single-dose pharmacokinetics over 24 hours rather than long-term tissue retention.
Cited by
- supports Magnesium oxide has very poor bioavailability compared to organic magnesium salts such as magnesium citrate, malate, taurate, and glycinate.