What is the bioavailability of magnesium glycinate?

Bioavailability of Magnesium Glycinate

Organic magnesium salts, including magnesium glycinate, have superior bioavailability compared to inorganic forms like magnesium oxide, which has only about 4% absorption. 1

Comparative Bioavailability of Magnesium Formulations

Magnesium supplements are available in various formulations with significant differences in bioavailability:

• Organic vs. Inorganic Forms:

  • Organic magnesium compounds (including glycinate) demonstrate better absorption than inorganic compounds 1, 2
  • Magnesium oxide has particularly poor bioavailability (only about 4% absorption) despite having higher elemental magnesium content 1, 3

• Specific Formulations:

  • Magnesium citrate shows the highest bioavailability among commonly used formulations 1, 4
  • In a randomized, double-blind study, magnesium citrate demonstrated superior bioavailability compared to magnesium oxide and other preparations 4
  • Magnesium glycinate, as an amino acid-bound compound, generally has good bioavailability similar to other organic forms 5

Factors Affecting Magnesium Absorption

Several factors influence the absorption of magnesium supplements:

• Dosing Strategy:

  • Smaller, divided doses throughout the day may improve relative absorption compared to a single large dose 1
  • Taking magnesium at night when intestinal transit is slower may improve absorption 1

• Dose-Dependency:

  • The percentage of absorption is dose-dependent, with higher doses having proportionally lower absorption rates 2
  • Research shows that dividing high doses of magnesium compounds did not sufficiently increase tissue magnesium levels 5

Clinical Implications

When considering magnesium supplementation:

• Formulation Selection:

  • For general supplementation, magnesium citrate is often recommended due to its high bioavailability 1
  • Magnesium glycinate is a good alternative, particularly for those who experience gastrointestinal side effects with other forms

• Special Populations:

  • Patients with significant renal impairment should avoid magnesium supplements due to the risk of hypermagnesemia 1
  • Older individuals or those with illnesses may not maintain physiological levels with supplementation as effectively as healthy individuals 2

Common Pitfalls and Considerations

• Bioavailability Assessment:

  • Measuring ionized magnesium in whole blood may be more sensitive for assessing acute oral intake compared to serum and urinary magnesium measurements 6

• Side Effects:

  • Higher doses of magnesium are more likely to cause diarrhea through the creation of an osmotic gradient in the intestinal lumen 1
  • Magnesium glycinate is often better tolerated than other forms, particularly magnesium oxide or citrate, which are more likely to cause gastrointestinal disturbances

• Monitoring:

  • Serum magnesium levels should be checked periodically to monitor effectiveness and safety 1
  • Assessment of symptom improvement while monitoring for side effects, particularly gastrointestinal, is important 1