October 2017

Magnesium – A Metal Essential to Life

Dr. Joseph E. Graas, Scientific Director
Dr. Edward Moore, Medical Director
Dr. Paul Robandt, Scientific Director

Magnesium is the ninth most abundant element in the universe, the eighth most abundant element in the earth’s crust, the fourth most common element in the earth and the third most abundant element dissolved in seawater.1-3

Magnesium is the eleventh most abundant element by mass in the human body and is essential to some 300 enzymes.  An adult body contains approximately 25 g magnesium, with 50% to 60% present in the bones and most of the rest in soft tissues.4 Adenosine triphosphate (ATP), the primary energy source for cells, must be bound to magnesium to be biologically active.  The synthesis of DNA and RNA requires the presence of magnesium for catalytic action.

The interaction of magnesium with enzymes can either alter the shape of an enzyme or take part in the chemistry of the enzymatic reaction itself.  Magnesium is a Lewis acid that can facilitate hydrolysis and condensation reactions (e.g. phosphate ester hydrolysis and phosphoryl transfer) that would not normally occur at physiological pH values. 5,6  The binding of magnesium to DNA and RNA stabilizes their structure, and many enzymes involved in nucleic acid synthesis bind magnesium for both activation and catalysis.  Magnesium also stabilizes cell membranes by binding to the lipids comprising them, thus regulating transport across the membrane.

Inadequate magnesium in the diet can cause weakness and muscle spasms in addition to being associated with cardiovascular disease and high blood pressure, migraines, anxiety disorder, osteoporosis and cerebral infarction. 7,8 Excess magnesium is not normally a problem in adults, as too much magnesium will cause diarrhea and magnesium is efficiently excreted by the renal system.  However, infants lack this efficiency so should not be given magnesium supplements except when under a physician’s care.

Assessing magnesium status is difficult because most magnesium is inside cells or in bone. The most commonly used and readily available method for assessing magnesium status is measurement of serum magnesium concentration, even though serum levels have little correlation with total body magnesium levels or concentrations in specific tissues. Other methods for assessing magnesium status include measuring magnesium concentrations in erythrocytes, saliva, and urine; measuring ionized magnesium concentrations in blood, plasma, or serum; and conducting a magnesium-loading (or “tolerance”) test. No single method is considered satisfactory.9

Magnesium may be measured in the laboratory by various gravimetric, titrimetric, electrochemical, spectrophotometric and mass spectrometric techniques, but is most easily analyzed by complexation followed by spectrophotometry.  The most commonly-used reagent for spectrophotometry of magnesium is xylidyl blue, which forms a red complex and is measured at 530 nanometers (green light) in the visible spectrum.  A complexing agent and detergents are added to inhibit interference from calcium and proteins in solution.10 This is a rapid, easily-automated analysis.

References

  1. Housecroft, C. E.; Sharpe, A. G. (2008). Inorganic Chemistry (3rd ed.). Prentice Hall. pp. 305–306. ISBN 978-0131755536.
  2. Ash, Russell (2005). The Top 10 of Everything 2006: The Ultimate Book of Lists. Dk Pub. ISBN 0-7566-1321-3. Archived from the original on 2006-10-05.
  3. Anthoni, J Floor (2006). “The chemical composition of seawater”. seafriends.org.nz.
  4. Volpe SL. Magnesium. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Ames, Iowa; John Wiley & Sons, 2012:459-74
  5. Black, C. B.; Cowan, J.A. (1995). J.A. Cowan, ed. “Magnesium-dependent enzymes in nucleic acid biochemistry”. The Biological Chemistry of Magnesium. New York: VCH.
  6. Cowan, J. A. (2002). “Structural and catalytic chemistry of magnesium-dependent enzymes”. BioMetals. 15 (3): 225–235. PMID 12206389. doi:10.1023/A:1016022730880.
  7. Romani, Andrea, M.P. (2013). “Chapter 3. Magnesium in Health and Disease”. In Astrid Sigel; Helmut Sigel; Roland K. O. Sigel. Interrelations between Essential Metal Ions and Human Diseases. Metal Ions in Life Sciences. 13. Springer. pp. 49–79. doi:10.1007/978-94-007-7500-8_3.
  8. Larsson S. C.; Virtanen M. J.; Mars M.; et al. (March 2008). “Magnesium, calcium, potassium, and sodium intakes and risk of stroke in male smokers”. Arch. Intern. Med. 168 (5): 459–65. PMID 18332289. doi:10.1001/archinte.168.5.459.
  9. Magnesium Fact Sheet for Health Professionals, National Institute of Health (Office of Dietary Supplements), 11 February 2016
  10. Magnesium XB Reagent Set product information, Pointe Scientific, Rev. 3/09 P803-HM929-01