Magnesium – A Metal Essential to Life
(Part 2)

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

Magnesium is a major intracellular ion, along with potassium.  It is a cofactor in many enzyme systems and therefore affects almost all organ systems resulting in a broad spectrum of clinical symptoms.  It is critical in regulating all electrical activity in the body, smooth muscle contraction, skeletal muscle contraction, brain activity, heart rhythm, and over three hundred various enzymatic reactions.

Clinicians most often encounter magnesium levels in the low range of less than 1.7 mg/dL (normal range 1.7 to 2.2 mg/dL).  This can be treated with either oral supplements or intravenously when severe.   Since magnesium is stored in bone and interstitial fluid, hypomagnesemia diagnosed via a blood test alone does not necessarily reflect magnesium deficiency.

Excessive magnesium is very rarely encountered, but when present, may result in central nervous system depression, prolonged cardiac atrioventricular conduction time, cardiac arrest and respiratory arrest.  Causes include those that affect renal glomerular filtration rate.

There are many clinically important situations in which hypomagnesemia is encountered including alcoholism, starvation, diarrhea, intestinal malabsorption, lactation, hypothyroidism, acute pancreatitis, aldosteronism, prolonged intravenous feeding, chronic glomerulonephritis, and increased urinary loss.  Symptoms include weakness, muscle cramps, arrhythmias, hypertension, neuromuscular irritability, tremors, palpitations, paresthesias (tingling, numbness, or burning pain), confusion and epileptic seizures.  It is interesting to note that hypomagnesemia can be seen approximately 30% of the time in cases involving alcohol abuse and 85% of the time when delirium tremens is present in withdrawal.

Magnesium is absorbed orally at about 30% bioavailability from any water soluble salt, such as magnesium chloride or magnesium citrate.  The least expensive soluble (high bioavailability) oral magnesium salt available in supplements is citrate.  Magnesium aspartate, chloride, lactate, citrate and glycinate each have bioavailability four times greater than the oxide form and are equivalent to each other per amount of magnesium.  To help absorption and decrease the incidence of diarrhea, time released or long acting preparations are better than simple salt.

Serum magnesium levels are ordered only as a follow up to chronically low blood levels of calcium and potassium, and frequently overlooked.  Serum tests may be ordered when a person has symptoms that may be due to a magnesium deficiency.  Considering the implication of magnesium in so many faculties and diverse roles in the body, it is important to focus on this as much as we think of the other electrolytes.  Magnesium is often called the “forgotten cation” and this doesn’t have to be the case.